@article {Kiazadeh2016, title = {Improving positive and negative bias illumination stress stability in parylene passivated IGZO transistors}, journal = {Applied Physics Letters}, volume = {109}, number = {5}, year = {2016}, note = {

cited By 0

}, abstract = {

The impact of a parylene top-coating layer on the illumination and bias stress instabilities of indium-gallium-zinc oxide thin-film transistors (TFTs) is presented and discussed. The parylene coating substantially reduces the threshold voltage shift caused by continuous application of a gate bias and light exposure. The operational stability improves by 75\%, and the light induced instability is reduced by 35\%. The operational stability is quantified by fitting the threshold voltage shift with a stretched exponential model. Storage time as long as 7 months does not cause any measurable degradation on the electrical performance. It is proposed that parylene plays not only the role of an encapsulation layer but also of a defect passivation on the top semiconductor surface. It is also reported that depletion-mode TFTs are less sensitive to light induced instabilities. This is attributed to a defect neutralization process in the presence of free electrons. {\textcopyright} 2016 Author(s).

}, doi = {10.1063/1.4960200}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981155175\&partnerID=40\&md5=ab02bba3454e040f574ba707d0f5408e}, author = {Kiazadeh, A.a b , Gomes, H.L.b c , Barquinha, P.a , Martins, J.a , Rovisco, A.a , Pinto, J.V.a , Martins, R.a , Fortunato, E.a} } @article {Bahubalindruni2016515, title = {Influence of Channel Length Scaling on InGaZnO TFTs Characteristics: Unity Current-Gain Cutoff Frequency, Intrinsic Voltage-Gain, and On-Resistance}, journal = {Journal of Display Technology}, volume = {12}, number = {6}, year = {2016}, note = {

cited By 0

}, pages = {515-518}, abstract = {

This paper presents a study concerning the role of channel length scaling on IGZO TFT technology benchmark parameters, which are fabricated at temperatures not exceeding 180\, ^{\circ}C. The parameters under investigation are unity current-gain cutoff frequency, intrinsic voltage-gain, and on-resistance of the bottom-gate IGZO TFTs. As the channel length varies from 160 to 3 μm, the measured cutoff frequency increases from 163 {\rm kHz} to 111.5 {\rm MHz}, which is a superior value compared to the other competing low-temperature thin-film technologies, such as organic TFTs. On the other hand, for the same transistor dimensions, the measured intrinsic voltage-gain is changing from 165 to 5.3 and the on-resistance is decreasing from 1135.6 to 26.1 k{\O}mega. TFTs with smaller channel length (3 μ m) have shown a highly negative turn-on voltage and hump in the subthreshold region, which can be attributed to short channel effects. The results obtained here, together with their interpretation based on device physics, provide crucial information for accurate IC design, enabling an adequate selection of device dimensions to maximize the performance of different circuit building blocks assuring the multifunctionality demanded by system-on-panel concepts. {\textcopyright} 2005-2012 IEEE.

}, doi = {10.1109/JDT.2016.2550610}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84975226429\&partnerID=40\&md5=687f1cb91fe43efa5721263d3371517a}, author = {Bahubalindruni, P.G.a , Kiazadeh, A.b , Sacchetti, A.b , Martins, J.b , Rovisco, A.b , Tavares, V.G.c , Martins, R.b , Fortunato} } @article {Lyubchyk20162317, title = {Influence of post-deposition annealing on electrical and optical properties of ZnO-based TCOs deposited at room temperature}, journal = {Physica Status Solidi (A) Applications and Materials Science}, volume = {213}, number = {9}, year = {2016}, note = {

cited By 0

}, pages = {2317-2328}, abstract = {

The post-deposition modification of ZnO-based transparent conductive oxides (TCOs) can be the key to produce thin films with optoelectronic properties similar to indium tin oxide (ITO), but at a much lower cost. Here, we present electro-optical results achieved for post-deposition annealing of Al{\textendash}Zn{\textendash}O (AZO), AZO:H, Ga{\textendash}Zn{\textendash}O:H (GZO:H), and Zn{\textendash}O:H (ZNO:H) thin films deposited by RF sputtering at room temperature. These studies comprise results of thermal annealing at atmospheric pressure, vacuum, forming gas, H2 and Ar atmospheres, and H2 and Ar plasmas, which lead to significant enhancement of their electro-optical properties, which are correlated to morphological and structural improvements. The post-deposition annealing leads to an enhancement in resistivity above 40\% for AZO, AZO:H, and GZO:H, reaching ρ ≈ 2.6{\textendash}3.5 {\texttimes} 10-4 Ωcm, while ZnO:H showed a lower improvement of 13\%. The averaged optical transmittance in the visible region is about 89\% for the investigated TCOs. Such results match the properties of state-of-art ITO (ρ ≈ 10-4 Ωcm and transmittance in VIS range of 90\%) employing much more earth-abundant materials. {\textcopyright} 2016 WILEY-VCH Verlag GmbH \& Co. KGaA, Weinheim

}, doi = {10.1002/pssa.201532891}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982994261\&partnerID=40\&md5=6f0dcdc9c81a8b2d1f6806fc96322f3c}, author = {Lyubchyk, A., Vicente, A., Alves, P.U., Catela, B., Soule, B., Mateus, T., Mendes, M.J., {\'A}guas, H., Fortunato, E., Martins, R.} } @article {Zubizarreta2016218, title = {The influence of target erosion grade in the optoelectronic properties of AZO coatings growth by magnetron sputtering}, journal = {Applied Surface Science}, volume = {380}, year = {2016}, note = {

cited By 0

}, pages = {218-222}, abstract = {

Aluminum-doped zinc oxide (AZO) transparent conductor coating has emerged as promising substitute to tin-doped indium oxide (ITO) as electrode in optoelectronic applications such as photovoltaics or light emitting diodes (LEDs). Besides its high transmission in the visible spectral region and low resistivity, AZO presents a main advantage over other candidates such as graphene, carbon nanotubes or silver nanowires; it can be deposited using the technology industrially implemented to manufacture ITO layers, the magnetron sputtering (MS). This is a productive, reliable and green manufacturing technique. But to guarantee the robustness, reproducibility and reliability of the process there are still some issues to be addressed, such as the effect and control of the target state. In this paper a thorough study of the influence of the target erosion grade in developed coatings has been performed. AZO films have been deposited from a ceramic target by RF MS. Structure, optical transmittance and electrical properties of the produced coatings have been analyzed as function of the target erosion grade. No noticeable differences have been found neither in optoelectronic properties nor in the structure of the coatings, indicating that the RF MS is a stable and consistent process through the whole life of the target. {\textcopyright} 2016 Elsevier B.V.

}, doi = {10.1016/j.apsusc.2016.01.147}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956679889\&partnerID=40\&md5=4936f4ce30d8cdc0381712bed0d3be11}, author = {Zubizarreta, C.a , G-Berasategui, E.a , Ciarsolo, I.a , Barriga, J.a , Gaspar, D.b , Martins, R.b , Fortunato, E.b} } @article {Ara{\'u}jo201618235, title = {Influence of the Substrate on the Morphology of Self-Assembled Silver Nanoparticles by Rapid Thermal Annealing}, journal = {Journal of Physical Chemistry C}, volume = {120}, number = {32}, year = {2016}, note = {

cited By 0

}, pages = {18235-18242}, abstract = {

Metal nanoparticles are of great interest for light trapping in photovoltaics. They are usually incorporated in the rear electrode of solar cells, providing strong light scattering at their surface plasmon resonances. In most cases, the nanoparticles are self-assembled by solid-state dewetting over a transparent conductive oxide (TCO) layer incorporated in the cell{\textquoteright}s rear electrode. Up to now, this process has been optimized mainly by tuning the thermal annealing parameters responsible for dewetting, or the thickness of the precursor metallic layer; but little attention has been paid to the influence of the underlying TCO layer properties on the morphology of the nanoparticles formed, which is the focus of the present article. This work investigates Ag nanoparticles structures produced on distinct surfaces by a simple, fast and highly reproducible method employing rapid thermal annealing. The results indicate that both the thermal conductivity and surface roughness of the TCO layer play a determinant role on the morphology of the nanostructures formed. This is of particular relevance, since we show in the study performed that the parasitic absorption of these Ag nanostructures is reduced, while the scattering is enhanced when the Ag nanostructures are formed on TCO layers with the highest conductivity and the lowest surface roughness (\~{}1 nm). These results unveil novel possibilities for the improvement of plasmonic nanostructures fabricated by thermal dewetting, via the careful adjustment of the physical properties of the underlying surface. {\textcopyright} 2016 American Chemical Society.

}, doi = {10.1021/acs.jpcc.6b04283}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983523367\&partnerID=40\&md5=04a6d23c9f55b5f3583cd9d3c1d6c372}, author = {Ara{\'u}jo, A., Mendes, M.J., Mateus, T., Vicente, A., Nunes, D., Calmeiro, T., Fortunato, E., {\'A}guas, H., Martins, R.} } @article {Bahubalindruni2016419, title = {InGaZnO thin-film-transistor-based four-quadrant high-gain analog multiplier on glass}, journal = {IEEE Electron Device Letters}, volume = {37}, number = {4}, year = {2016}, note = {

cited By 0

}, pages = {419-421}, abstract = {

This letter presents a novel high-gain four-quadrant analog multiplier using only n-type enhancement indium- gallium-zinc-oxide thin-film-transistors. The proposed circuit improves the gain by using an active load with positive feedback. A Gilbert cell with a diode-connected load is also presented for comparison purposes. Both circuits were fabricated on glass at low temperature (200 {\textdegree}C) and were successfully characterized at room temperature under normal ambient conditions, with a power supply of 15 V and 4-pF capacitive load. The novel circuit has shown a gain improvement of 7.2 dB over the Gilbert cell with the diode-connected load. Static linearity response, total harmonic distortion, frequency response, and power consumption are reported. This circuit is an important signal processing building block in large-area sensing and readout systems, specially if data communication is involved. {\textcopyright} 2016 IEEE.

}, doi = {10.1109/LED.2016.2535469}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963839212\&partnerID=40\&md5=2d6c653ce01a9594eae321daaf5151c2}, author = {Bahubalindruni, P.G.a , Tavares, V.G.b , Borme, J.c , De Oliveira, P.G.b , Martins, R.a , Fortunato, E.a , Barquinha, P.a} } @article {Bernacka-Wojcik2016208, title = {Inkjet printed highly porous TiO2 films for improved electrical properties of photoanode}, journal = {Journal of Colloid and Interface Science}, volume = {465}, year = {2016}, note = {

cited By 1

}, pages = {208-214}, abstract = {

The aim of presented work is to show the improvements obtained in the properties of TiO2 films for dye sensitized solar cells fabricated by inkjet printing using an innovative methodology. We describe the development and properties of TiO2-based inks used in a lab-scale printer, testing various commercial TiO2 pastes. The porosity of the deposited inkjet printed TiO2 films is much higher than using the conventional "doctor blade" deposition technique, as the ink solvent evaporates during the droplet fly from the nozzle to the substrate due to its picoliter volume and the applied heating of a printing stage (70{\textdegree}C). Thanks to higher surface area, the dye sensitized solar cells incorporating inkjet printed TiO2 film gave higher efficiencies (ηmax≈3.06\%) than the more compact films obtained by the "doctor blade" method (ηmax≈2.56\%). Furthermore, electrochemical analysis indicates that for whole tested thickness range, the inkjet printed layers have higher effective electron diffusion length indicating their better transport properties. {\textcopyright} 2015 Elsevier Inc..

}, doi = {10.1016/j.jcis.2015.11.070}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949845705\&partnerID=40\&md5=dfd09ca0f5ea733f88ccc7526af80904}, author = {Bernacka-Wojcik, I.a b , Wojcik, P.J.a b , Aguas, H.a , Fortunato, E.a , Martins, R.a} } @article {Jin2016, title = {Interpreting anomalies observed in oxide semiconductor TFTs under negative and positive bias stress}, journal = {AIP Advances}, volume = {6}, number = {8}, year = {2016}, note = {

cited By 0

}, abstract = {

Oxide semiconductor thin-film transistors can show anomalous behavior under bias stress. Two types of anomalies are discussed in this paper. The first is the shift in threshold voltage (VTH) in a direction opposite to the applied bias stress, and highly dependent on gate dielectric material. We attribute this to charge trapping/detrapping and charge migration within the gate dielectric. We emphasize the fundamental difference between trapping/detrapping events occurring at the semiconductor/dielectric interface and those occurring at gate/dielectric interface, and show that charge migration is essential to explain the first anomaly. We model charge migration in terms of the non-instantaneous polarization density. The second type of anomaly is negative VTH shift under high positive bias stress, with logarithmic evolution in time. This can be argued as electron-donating reactions involving H2O molecules or derived species, with a reaction rate exponentially accelerated by positive gate bias and exponentially decreased by the number of reactions already occurred. {\textcopyright} 2016 Author(s).

}, doi = {10.1063/1.4962151}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984677284\&partnerID=40\&md5=f3cff1341caca5041c8a817faa91e99f}, author = {Jin, J.W.a , Nathan, A.b , Barquinha, P.c , Pereira, L.c , Fortunato, E.c , Martins, R.c , Cobb, B.d} } @article {Gaspar2013, title = {Influence of the layer thickness in plasmonic gold nanoparticles produced by thermal evaporation}, journal = {Scientific Reports}, volume = {3}, year = {2013}, note = {

cited By 23

}, abstract = {

Metallic nanoparticles (NPs) have received recently considerable interest of photonic and photovoltaic communities. In this work, we report the optoelectronic properties of gold NPs (Au-NPs) obtained by depositing very thin gold layers on glass substrates through thermal evaporation electron-beam assisted process. The effect of mass thickness of the layer was evaluated. The polycrystalline Au-NPs, with grain sizes of 14 and 19 nm tend to be elongated in one direction as the mass thickness increase. A 2 nm layer deposited at 250 C led to the formation of Au-NPs with 10-20 nm average size, obtained by SEM images, while for a 5 nm layer the wide size elongates from 25 to 150 nm with a mean at 75 nm. In the near infrared region was observed an absorption enhancement of amorphous silicon films deposited onto the Au-NPs layers with a corresponding increase in the PL peak for the same wavelength region.

}, doi = {10.1038/srep01469}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876533482\&partnerID=40\&md5=38d58ebe9cddcbd08fe83d79ea94226f}, author = {Gaspar, D.a , Pimentel, A.C.a , Mateus, T.a , Leit{\~a}o, J.P.b , Soares, J.b , Falc{\~a}o, B.P.b , Ara{\'u}jo, A.a , Vicente, A.a , Filonov} } @conference {Kondaiah2012, title = {Influence of substrate bias voltage on the physical, electrical and dielectric properties of RF magnetron sputtered TiO 2 films}, booktitle = {IOP Conference Series: Materials Science and Engineering}, volume = {30}, number = {1}, year = {2012}, note = {

cited By 1

}, abstract = {

Titanium oxide (TiO 2) finds potential applications in various fields such as solar cells, optical coatings due to its high refractive index and it also has been widely used in memory devices owing to its high dielectric constant. TiO 2 films have been deposited on p-type silicon (100) substrates by RF magnetron sputtering technique. Thickness, structure and surface morphology of the films were analyzed by using α-step profilometer, Raman spectroscopy and atomic force microscope respectively. Thin film capacitors of the type Al/TiO 2/Si were fabricated by evaporation of Aluminium on to the TiO 2 films. The current - voltage and capacitance - voltage characteristics were carried out to understand the electrical conduction and dielectric properties of the deposited films with a stack of Al/TiO 2/Si. The leakage current density was decreased and capacitance was increased with increase of substrate bias voltage.

}, doi = {10.1088/1757-899X/30/1/012005}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858213569\&partnerID=40\&md5=1b5b835ce4fd25ade17f0c92018b5bd6}, author = {Kondaiah, P.a , Sekhar, M.C.a , Chandra, S.V.J.b , Martins, R.b , Uthanna, S.a , Elangovan, E.b} } @article {Gokulakrishnan2012589, title = {Investigation of O 7+ swift heavy ion irradiation on molybdenum doped indium oxide thin films}, journal = {Radiation Physics and Chemistry}, volume = {81}, number = {6}, year = {2012}, note = {

cited By 6

}, pages = {589-593}, abstract = {

Molybdenum (0.5at\%) doped indium oxide thin films deposited by spray pyrolysis technique were irradiated by 100MeV O 7+ ions with different fluences of 5{\texttimes}10 11, 1{\texttimes}10 12 and 1{\texttimes}10 13ions/cm 2. Intensity of (222) peak of the pristine film was decreased with increase in the ion fluence. Films irradiated with the maximum ion fluence of 1{\texttimes}10 13ions/cm 2 showed a fraction of amorphous nature. The surface microstructures on the surface of the film showed that increase in ion fluence decreases the grain size. Mobility of the pristine molybdenum doped indium oxide films was decreased from ~122 to 48cm 2/Vs with increasing ion fluence. Among the irradiated films the film irradiated with the ion fluence of 5{\texttimes}10 11ions/cm 2 showed relatively low resistivity of 6.7{\texttimes}10 -4Ωcm with the mobility of 75cm 2/Vs. The average transmittance of the as-deposited IMO film is decreased from 89\% to 81\% due to irradiation with the fluence of 5{\texttimes}10 11ions/cm 2. {\textcopyright} 2012 Elsevier Ltd.

}, doi = {10.1016/j.radphyschem.2012.02.037}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859705759\&partnerID=40\&md5=34854fc0c82b187eddac1eecafa59fa3}, author = {Gokulakrishnan, V.a , Parthiban, S.a c , Elangovan, E.c , Jeganathan, K.b , Kanjilal, D.d , Asokan, K.d , Martins, R.c , Fortuna} } @article {Wang20102674, title = {Influence of deposition pressure on N-doped ZnO films by RF magnetron sputtering}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {10}, number = {4}, year = {2010}, note = {

cited By 3

}, pages = {2674-2678}, abstract = {

N-doped ZnO films were deposited on glass substrates by RF magnetron sputtering with different deposition pressures. The samples were characterized by X-ray diffraction (XRD), atomic force morphology (AFM), X-ray photoelectron spectroscopy (XPS), Hall measurements and optical spectrophotometer. The XRD patterns confirmed that the films are polycrystalline and the influence of deposition pressure on the structural properties. AFM microstructures also authenticated the change in the size and shape of the grains as a function of deposition pressure; the root mean square (RMS) roughness has reached a maximum (10.65 nm) at 1.5 x 10 -2 mbar. XPS spectra revealed the change in the chemical composition. The amount of adsorbed oxygen and nitrogen at oxide sites has reached the maximum at 9.0 x 10 -3 mbar, where the film showed p-type conductivity. The optical transmittance spectra have indicated that the absorption edge is shifted towards the shorter wavelength at higher deposition pressure. Correspondingly, the optical band gap is increased from 2.17 to 2.80 eV. The average visible transmittance in the wavelength ranging 500-800 nm has been increased from 49\% to 82\%. Copyright {\textcopyright} 2010 American Scientific Publishers All rights reserved.

}, doi = {10.1166/jnn.2010.1401}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954993809\&partnerID=40\&md5=29d2991a74d06de0753ea9a728a0764a}, author = {Wang, J.a , Elamurugu, E.a , Franco, N.b , Alves, E.b , Botelho Do Rego, A.M.c , Gon{\c c}alves, G.a , Martins, R.a , Fortunato, E.a} } @article {Wang20102326, title = {Influence of oxygen partial pressure on properties of N-doped ZnO films deposited by magnetron sputtering}, journal = {Transactions of Nonferrous Metals Society of China (English Edition)}, volume = {20}, number = {12}, year = {2010}, note = {

cited By 5

}, pages = {2326-2330}, abstract = {

N-doped ZnO films were radio frequency (RF) sputtered on glass substrates and studied as a function of oxygen partial pressure (OPP) ranging from 3.0{\texttimes}10-4 to 9.5{\texttimes}10-3 Pa. X-ray diffraction patters confirmed the polycrystalline nature of the deposited films. The crystalline structure is influenced by the variation of OPP. Atomic force microscopy analysis confirmed the agglomeration of the neighboring spherical grains with a sharp increase of root mean square (RMS) roughness when the OPP is increased above 1.4{\texttimes}10-3 Pa. X-ray photoelectron spectroscopy analysis revealed that the incorporation of N content into the film is decreased with the increase of OPP, noticeably N 1s XPS peaks are hardly identified at 9.5{\texttimes}10-3 Pa. The average visible transmittance (380-700 nm) is increased with the increase of OPP (from \~{}17 to 70), and the optical absorption edge shifts towards the shorter wavelength. The films deposited with low OPP (<= 3.0{\texttimes}10-4 Pa) show n-type conductivity and those deposited with high OPP (>= 9.0{\texttimes}10-4 Pa) are highly resistive (\>105 {\textperiodcentered}cm) {\textcopyright} 2010 The Nonferrous Metals Society of China.

}, doi = {10.1016/S1003-6326(10)60649-8}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651074162\&partnerID=40\&md5=56c6c73b6903f0e78e69ca34c4238d7c}, author = {Wang, J.-Z.a b , Elangovan, E.b , Franco, N.c , Alvese, A.c , Rego, A.d , Martins, R.b , Fortunato, E.b} } @article {Bernacka-Wojcik20101229, title = {Inkjet printed and "doctor blade" TiO2 photodetectors for DNA biosensors}, journal = {Biosensors and Bioelectronics}, volume = {25}, number = {5}, year = {2010}, note = {

cited By 28

}, pages = {1229-1234}, abstract = {

A dye sensitized TiO2 photodetector has been integrated with a DNA detection method based on non-cross-linking hybridization of DNA-functionalized gold nanoparticles, resulting in a disposable colorimetric biosensor. We present a new approach for the fabrication of dye sensitized TiO2 photodetectors by an inkjet printing technique-a non-contact digital, additive, no mask and no vacuum patterning method, ideal for cost efficient mass production. The developed biosensor was compared against a dye sensitized photodetector fabricated by the traditional "doctor blade" method. Detection of gold nanoparticle aggregation was possible for concentrations as low as 1.0 nM for the "doctor blade" system, and 1.5 nM for the inkjet printed photodetector. The demonstrated sensitivity limits of developed biosensors are comparable to those of spectrophotometric techniques (1.0 nM). Our results show that a difference higher than 17\% by traditional photodetector and 6\% by inkjet printed in the photoresponses for the complementary and non-complementary gold nanoprobe assays could be attained for a specific DNA sequence from Mycobacterium tuberculosis, the etiologic agent of human tuberculosis. The decrease of costs associated with molecular diagnostic provided by a platform such as the one presented here may prove of paramount importance in developing countries. {\textcopyright} 2009 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.bios.2009.09.027}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149094849\&partnerID=40\&md5=5a7a74e727bbc691efc26e51a326e84d}, author = {Bernacka-Wojcik, I.a , Senadeera, R.a b , Wojcik, P.J.a , Silva, L.B.a , Doria, G.c d , Baptista, P.c , Aguas, H.a , Fortunato,} } @article {Olziersky2010, title = {Insight on the SU-8 resist as passivation layer for transparent Ga 2 O3 - In2 O3-ZnO thin-film transistors}, journal = {Journal of Applied Physics}, volume = {108}, number = {6}, year = {2010}, note = {

cited By 32

}, abstract = {

{A nonvacuum and low temperature process for passivating transparent metal oxides based thin-film transistors is presented. This process uses the epoxy-based SU-8 resist which prevents device degradation against environmental conditions, vacuum or sputtering surface damage. The incorporation of SU-8 as a passivation layer is based on the ability of this polymer to provide features with high mechanical and chemical stability. With this approach, lithography is performed to pattern the resist over the active area of the device in order to form the passivation layer. The resulting transistors demonstrate very good electrical characteristics, such as μFE =61 cm2 /V s

}, doi = {10.1063/1.3477192}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957740514\&partnerID=40\&md5=c035abb8be52b3a1285c1065b6c55e3c}, author = {Olziersky, A.a , Barquinha, P.b , Vil̀, A.a , Pereira, L.b , Gonalves, G.b , Fortunato, E.b , Martins, R.b , Morante, J.R.a c} } @article {Parthiban2010406, title = {Investigations on high visible to near infrared transparent and high mobility Mo doped In2O3 thin films prepared by spray pyrolysis technique}, journal = {Solar Energy Materials and Solar Cells}, volume = {94}, number = {3}, year = {2010}, note = {

cited By 35

}, pages = {406-412}, abstract = {

High visible to near infrared (NIR) transparent Mo (0-1 at\%) doped In2O3 (IMO) thin films with high carrier mobility were deposited on Corning-1737 glass substrates at 400 {\textdegree}C by spray pyrolysis experimental technique. The films were annealed in vacuum (\~{}1{\texttimes}10-4 mbar) at 550 {\textdegree}C for 45 min. XRD analysis confirmed that indium oxide belongs to cubic bixbyite structure. The preferred growth orientation along (2 2 2) plane for low Mo doping level shifts to (4 0 0) for higher Mo doping levels. Crystallite sizes extracted from the XRD data corroborate the changes in full-width at half-maximum due to the variation in Mo doping. Scanning electron microscopy study illustrates the evolution in surface microstructures as a function of Mo doping. The negative sign of Hall coefficient confirmed n-type conductivity. Films with high mobility of \~{}149 cm2/(V s), carrier concentration of \~{}1.0{\texttimes}1020 cm-3, resistivity of \~{}4.0{\texttimes}10-4 Ω cm and high figure of merit of \~{}1.02{\texttimes}10-2 Ω-1 were observed for post-annealed films (0.5 at\% Mo). The obtained high average transparency of \~{}83\% in the wavelength range 400-2500 nm confirms that transmittance is well extended into the NIR region. {\textcopyright} 2009 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.solmat.2009.10.017}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-75149167355\&partnerID=40\&md5=d9b4a2a7b5c28cbbdd92c9df6fc4a80e}, author = {Parthiban, S.a , Elangovan, E.b , Ramamurthi, K.a , Martins, R.b , Fortunato, E.b} } @article {Elangovan20092123, title = {Indium molybdenum oxide thin films: A comparative study by two different RF sputtering systems}, journal = {Physica Status Solidi (A) Applications and Materials Science}, volume = {206}, number = {9}, year = {2009}, note = {

cited By 3

}, pages = {2123-2127}, abstract = {

Indium molybdenum oxide thin films were deposited using different radio-frequency sputtering units on glass substrates at room temperature from an In 2O 3 (95 wt.\%): Mo (5 wt.\%) target. The film thickness ranges between 160 and 275 nm. The chamber volume of Unit-1 was ̃2.4 times larger than that of Unit-2. Apart from the chamber volume, a significant difference between the two units was the sputtering pressure. The films were characterized by their structural, morphological, optical, and electrical properties. A strong reflection from (222) plane was obtained for the ̃275 nm thick films deposited in Unit-1. The films deposited with \<275 nm thickness and those deposited in Unit-2 are close to amorphous with a small crystalline fraction. The surface of the films deposited in Unit-1 is comprised of randomly arranged crystallites, which is restructured with the increasing film thickness to become a well defined "rice field" like structure (275 nm thick). The films deposited in Unit-2 are comprised of many holes on the surface that is presumably due to back sputtering. The average visible transmittance calculated in the wavelength between 400 and 800 nm ranges from 70 to 82\%. The optical band gap is found to vary between 3.80 and 3.86 eV. The lowest bulk resistivity of the films deposited in Unit-1 was increased from ̃4.06{\texttimes}10 -3 to 4.07{\texttimes}10 -1ωcm when deposited in Unit-2. The carrier concentration was decreased from 1.31{\texttimes}10 20 to 1.03{\texttimes}10 18 cm -3 but the Hall mobility increased from 11.7 to 15.0 cm2 V -1 s -1. {\textcopyright} 2009 WILEY-VCH Verlag GmbH \& Co. KGaA, Weinheim.

}, doi = {10.1002/pssa.200881796}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349136686\&partnerID=40\&md5=e4e298151cf9ed7abe77db17739dd05d}, author = {Elangovan, E., Martins, R., Fortunato, E.} } @article {Wang2009813, title = {Intrinsic P type ZNO films deposited by RF magnetron sputtering}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {9}, number = {2}, year = {2009}, note = {

cited By 6

}, pages = {813-816}, abstract = {

ZnO films were deposited on c-plane sapphire substrates in Ar atmosphere by ii magnetron sputtering and were post-annealed at 400{\textdegree}C in green gas (95\% N2 + 5\% H2). The properties of the as-grown and annealed films have been characterized by X-ray diffraction (XRD), Rutherford backscattering (RBS), elastic recoil detection analysis (ERDA), Hall measurement and photoluminescence spectra. XRD studies confirmed the variation in strain and an improvement in crystallinity. From RBS and ERDA analysis, the presence of H atoms on the surface of the as-grown ZnO films was evidenced. Annealing in green gas increased the amount of H in the film. Compared with the as-grown films, the ultra exciting intensity obviously decreases in the annealed films and new optical active centres in the blue/violet (~3.0 eV) and red (~1.9) regions are emerged in the PL spectrum. The positive sign of Hall coefficient confirmed the low (-type conductivity in the as grown films, which was improved after annealing. However, the (-type conductivity was not stable, especially for the annealed sample it changes from ( type to n type after 9 days. Copyright {\textcopyright} 2009 American Scientific Publishers All rights reserved.

}, doi = {10.1166/jnn.2009.C030}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349240322\&partnerID=40\&md5=8ac1b9200580d42fb22574ce9cd70357}, author = {Wang, J.a , Martins, R.a , Barradas, N.P.c , Alves, E.c , Monteiro, T.b , Peres, M.b , Elamurugu, E.a , Fortunato, E.a} } @article {Martins20082580, title = {Identification of unamplified genomic DNA sequences using gold nanoparticle probes and a novel thin film photodetector}, journal = {Journal of Non-Crystalline Solids}, volume = {354}, number = {19-25}, year = {2008}, note = {

cited By 7

}, pages = {2580-2584}, abstract = {

This paper describes a novel colorimetric method for detection of nucleic acid targets in a homogeneous format with improved sensitivity by means of a system based on the combination of a tunable monochromatic light source and an amorphous/nanocrystalline silicon photodetector that detects color and light intensity changes undergone by samples/assays containing tailored gold nanoparticles probes. This new low cost, portable, fast and simple optoelectronic platform, with the possibility to be re-used, permits detection of at least 400 fentomole of specific DNA sequences without target or signal amplification and was applied to the rapid detection of human pathogens in large variety of clinical samples such as Mycobacterium tuberculosis. {\textcopyright} 2008 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.jnoncrysol.2007.09.074}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-43049117461\&partnerID=40\&md5=e463cecb6fa64b0984a4de8b23a0e711}, author = {Martins, R.a , Baptista, P.b , Silva, L.a , Raniero, L.a d , Doria, G.b c , Franco, R.c , Fortunato, E.a} } @article {Wang2008242, title = {Influence of different carrier gases on the properties of ZnO films grown by MOCVD}, journal = {Boletin de la Sociedad Espanola de Ceramica y Vidrio}, volume = {47}, number = {4}, year = {2008}, note = {

cited By 1

}, pages = {242-244}, abstract = {

ZnO films were grown on sapphire (001) substrate by atmospheric MOCVD using diethyl zinc and tertiary butanol precursors. The influence of different carrier gases (H2 and He) on the properties was analyzed by their structural (XRD), microstructural (SEM) and compositional (SIMS) characterization. The intensity of the strongest diffraction peak from ZnO (002) plane was increased by about 2 orders of magnitude when He is used as carrier gas, indicating the significant enhancement in crystallinity. The surface of the samples grown using H2 and He carrier gases was composed of leaf-like and spherical grains respectively. Hydrogen [H] content in the film grown using H2 is higher than that using He, indicating that the [H] was influenced by the H2 carrier gas. Ultraviolet emission dominates the low temperature PL spectra. The emission from ZnO films grown using He show higher optical quality and more emission centers.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-54949098522\&partnerID=40\&md5=ff52a06346956a17a55b38ac25b766bd}, author = {Wang, J.a , Elamurugu, E.a , Sallet, V.b , Lusson, A.b , Amiri, G.b , Jomard, F.b , Martins, R.a , Fortunato, E.a} } @article {Cui20081507, title = {Influence of oxygen/argon pressure ratio on the morphology, optical and electrical properties of ITO thin films deposited at room temperature}, journal = {Vacuum}, volume = {82}, number = {12}, year = {2008}, note = {

cited By 29

}, pages = {1507-1511}, abstract = {

Transparent conductive oxides (TCOs) such as indium tin oxide (ITO) thin films onto glass substrates are widely used as transparent and conductive electrodes for a variety of technological applications including flat panel displays, solar cells, smart windows, touch screens, etc. ITO films on glass and polycarbonate (PC) substrates were prepared at room temperature (RT) and at different PO2. The films were characterized in terms of the surface roughness (δ), sheet resistance, the refractive index (n) and extinction coefficient (k). The free carrier density (nc) and the carrier mobility (μ) of the ITO (In2O3:Sn) films were measured and studied. The nc and μ values vary in different ratio of oxygen partial pressure (PO2) of ITO deposition. The observed changes in the ITO film resistivity are due to the combined effect of different parameter values for nc and μ. From AFM analysis and spectra calculations, the surface roughness values of the ITO films were studied and it was observed that the δ values were lower than 15 nm. The energy band gap Eg ranges from 3.26 eV to 3.66 eV as determined from the absorption spectrum. It was observed an increase on the energy band gap as the PO2 decrease in the range of 20-2\% PO2. The Lorentz oscillator classical model has also been used to fit the ellipsometric spectra in order to obtain both refractive index n and extinction coefficient κ values. {\textcopyright} 2008 Elsevier Ltd. All rights reserved.

}, doi = {10.1016/j.vacuum.2008.03.061}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-49249130712\&partnerID=40\&md5=e05a0deef745ddd0e174da4e8a0b9e00}, author = {Cui, H.-N.a , Teixeira, V.a , Meng, L.-J.b , Martins, R.c , Fortunato, E.c} } @article {Prabakaran20082610, title = {Investigation of hydrocarbon coated porous silicon using PECVD technique to detect CO2 gas}, journal = {Journal of Non-Crystalline Solids}, volume = {354}, number = {19-25}, year = {2008}, note = {

cited By 3

}, pages = {2610-2614}, abstract = {

In the present work, we investigate the influence of hydrocarbon (CHx) thin film coating on porous silicon (PS) by plasma enhanced chemical vapor deposition (PECVD) technique to detect CO2 gas. The fabricated CHx/PS heterojunction device shows up to one and two orders of magnitude enhancement in current under CO2 gas exposure. FTIR spectroscopy measurements reveal a remarkable structural modification of the CHx/PS device during CO2 gas exposure. Further, the enhancement of CHx related absorbance bands by a factor 6.2 for the CHx/PS specimen in comparison with PS confirm the good quality of the deposited CHx thin films. {\textcopyright} 2007 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.jnoncrysol.2007.10.101}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-43049117472\&partnerID=40\&md5=70ff473fea519df9080a1b80d84a9233}, author = {Prabakaran, R., Silva, L., Fortunato, E., Martins, R., Ferreira, I.} } @article {Gon{\c c}alves20078562, title = {Influence of post-annealing temperature on the properties exhibited by ITO, IZO and GZO thin films}, journal = {Thin Solid Films}, volume = {515}, number = {24 SPEC. ISS.}, year = {2007}, note = {

cited By 85

}, pages = {8562-8566}, abstract = {

In this work we present a study on the effect of annealing temperatures on the structural, morphological, electrical and optical characteristics of gallium doped zinc oxide (GZO), indium zinc oxide (IZO) and indium-tin-oxide (ITO) films. GZO and IZO films were deposited at room temperature by r.f. magnetron sputtering, whereas the ITO films were commercial ones purchased from Balzers. All films were annealed at temperatures of 250 and 500~{\textdegree}C in open air for 1 h. The GZO and ITO films were polycrystalline. The amorphous structure of as-deposited IZO films becomes crystalline on high temperature annealing (500~{\textdegree}C). The sheet resistivity increased with increase in annealing temperature. GZO films showed an increase of 6 orders of magnitude. The optical transmittance and band gap of as-deposited films varied with annealing. The highest transmittance (over 95 \%) and maximum band gap (3.93~eV) have been obtained for ITO films. {\textcopyright} 2007 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.tsf.2007.03.126}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548859816\&partnerID=40\&md5=267b751d0606809c2517387c924b8574}, author = {Gon{\c c}alves, G., Elangovan, E., Barquinha, P., Pereira, L., Martins, R., Fortunato, E.} } @article {Wang20078785, title = {Influence of substrate temperature on N-doped ZnO films deposited by RF magnetron sputtering}, journal = {Thin Solid Films}, volume = {515}, number = {24 SPEC. ISS.}, year = {2007}, note = {

cited By 24

}, pages = {8785-8788}, abstract = {

Nitrogen-doped ZnO films were deposited by RF magnetron sputtering in 75\% of N2 / (Ar + N2) gas atmosphere. The influence of substrate temperature ranging from room temperature (RT) to 300~{\textdegree}C was analyzed by X-ray diffractometry (XRD), spectrophotometry, X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS) and Hall measurements setup. The XRD studies confirmed the hexagonal ZnO structure and showed that the crystallinity of these films increased with increasing substrate temperature (Ts). The optical studies indicate the average visible transmittance in the wavelength ranging 500-800~nm increases with increasing Ts. A minimum transmittance (9.84\%) obtained for the films deposited at RT increased with increasing Ts to a maximum of 88.59\% at 300~{\textdegree}C (500-800~nm). Furthermore, it was understood that the band gap widens with increasing Ts from 1.99~eV (RT) to 3.30~eV (250~{\textdegree}C). Compositional analyses (XPS and SIMS) confirmed the nitrogen (N) incorporation into the ZnO films and its decreasing concentration with increasing Ts. The negative sign of Hall coefficients confirmed the n-type conducting. {\textcopyright} 2007 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.tsf.2007.03.061}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548840549\&partnerID=40\&md5=3215ee9c0dff23875eaa9f3bb4d674cb}, author = {Wang, J.a , Sallet, V.b , Jomard, F.b , Botelho do Rego, A.M.c , Elamurugu, E.a , Martins, R.a , Fortunato, E.a} } @article {Wang20078780, title = {Influence of the reactive N2 gas flow on the properties of rf-sputtered ZnO thin films}, journal = {Thin Solid Films}, volume = {515}, number = {24 SPEC. ISS.}, year = {2007}, note = {

cited By 25

}, pages = {8780-8784}, abstract = {

Nitrogen (N)-doped ZnO thin films were RF sputtered with different N2 volume (ranging from 10\% to 100\%) on sapphire (001) substrates. The influence of N2 vol.\% on the properties of ZnO films was analyzed by various characterization techniques. The X-ray diffraction studies showed that the films grow along the preferential (002) crystallographic plane and the crystallinity varied with varying N2 vol.\%. The films sputtered with 25~vol.\% N2 showed better crystallinity. The transmittance was decreased with increasing N2 volume until 25\% and was almost constant above 25\%. A maximum optical band gap (2.08~eV) obtained for 10~vol.\% N2 decreased with increasing N2 volume to reach a minimum of 1.53~eV at 100\%. The compositional analysis confirmed the incorporation of N into ZnO films, and its concentration increased with increasing N2 volume to reach a maximum of \~{} 3.7 {\texttimes} 1021~atom/cm3 at 75\% but then decreased slightly to 3.42 {\texttimes} 1021~atoms/cm3. The sign of Hall coefficient confirmed that the films sputtered with <= 25~vol.\% N2 possess p-type conductivity which changes to n-type for \> 25~vol.\% N2. {\textcopyright} 2007 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.tsf.2007.03.062}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548827052\&partnerID=40\&md5=f043056a98a20b71a1e8c6dd5c9d9c9d}, author = {Wang, J.a , Sallet, V.b , Jomard, F.b , Botelho do Rego, A.M.c , Elamurugu, E.a , Martins, R.a , Fortunato, E.a} } @article {Pereira20061737, title = {Impedance study of the electrical properties of poly-Si thin film transistors}, journal = {Journal of Non-Crystalline Solids}, volume = {352}, number = {9-20 SPEC. ISS.}, year = {2006}, note = {

cited By 4

}, pages = {1737-1740}, abstract = {

The aim of this work is to study the electrical characteristics of polycrystalline silicon (poly-Si) thin film transistors (TFTs) using spectroscopic impedance technique, where the poly-Si active layer was obtained by metal induced crystallization of amorphous silicon. From the study performed a theoretical model that fitted the impedance data is proposed, in order to obtain the separate contributions of each region that constitutes the TFT namely the channel, non accumulated region and contacts. {\textcopyright} 2006 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.jnoncrysol.2006.01.066}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745454055\&partnerID=40\&md5=e6cf3e25b2383f0c6528bcefe983fda4}, author = {Pereira, L., Raniero, L., Barquinha, P., Fortunato, E., Martins, R.} } @conference {Wang20061010, title = {Influence of the ex-situ and in-situ annealed self-buffer layer on ZnO film}, booktitle = {Physica Status Solidi C: Conferences}, volume = {3}, number = {4}, year = {2006}, note = {

cited By 1

}, pages = {1010-1013}, abstract = {

Two self-buffer layers were grown on c-plane sapphire substrates by atmospheric MOCVD method using DEZn, tert-butanol as precursors and H 2 as carrier gas. Then, they were respectively annealed in growth process and oxygen environment. After that, ZnO films were respectively grown on them. XRD spectra show that all the films were grown in [002] orientation. Furthermore, the film with a buffer layer annealed in oxygen exhibits much higher crystal quality. Its FWHM of the rocking curve is only 567arcsec. Furthermore, its Raman scattering spectrum appears a much stronger E2 mode peak at 436cm-1 and its PL spectrum appears a shoulder at 3.367eV on the higher energy side. {\textcopyright} 2006 WILEY-VCH Verlag GmbH \& Co. KGaA,.

}, doi = {10.1002/pssc.200564704}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646242258\&partnerID=40\&md5=b1d58b240fe670937288805b904e49c3}, author = {Wang, J.c , Sallet, V.a , Amiri, G.a , Rommelluere, J.-F.a , Lusson, A.a , Rzepka, E.a , Lewis, J.E.b , Galtier, P.a , Fortunato} } @article {Wang20061527, title = {Influence of the self-buffer layer on ZnO film grown by atmospheric metal organic chemical vapor deposition}, journal = {Thin Solid Films}, volume = {515}, number = {4}, year = {2006}, note = {

cited By 2

}, pages = {1527-1531}, abstract = {

ZnO films with and without a self-buffer layer were grown on c-plane sapphire substrates by atmospheric metal organic chemical vapor deposition. The influence of the buffer layer thickness, annealing temperature and annealing time on ZnO films has been investigated. The full width at half maximum of the ω-rocking curve of the optimized self-buffer layer sample is only 395~arc~sec. Its surface is composed of regular columnar hexagons. After the buffer layer was introduced, the A1 longitudinal mode peak at 576~cm- 1, related to the defects, disappears in Raman spectra. For the photoluminescence, besides the strong donor binding exciton peak at 3.3564~eV, an ionized donor binding exciton and a free exciton peak is respectively observed at 3.3673 and 3.3756~eV at the high-energy side in the spectrum of the sample with the buffer layer. {\textcopyright} 2006 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.tsf.2006.04.027}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750842088\&partnerID=40\&md5=00eda684de22b4e898c7bcaecca38756}, author = {Wang, J.c , Sallet, V.a , Amiri, G.a , Rommelluere, J.-F.a , Lusson, A.a , Lewis, J.E.b , Galtier, P.a , Fortunato, E.c , Martin} } @article {Barquinha20061749, title = {Influence of the semiconductor thickness on the electrical properties of transparent TFTs based on indium zinc oxide}, journal = {Journal of Non-Crystalline Solids}, volume = {352}, number = {9-20 SPEC. ISS.}, year = {2006}, note = {

cited By 148

}, pages = {1749-1752}, abstract = {

Multicomponent amorphous oxides are starting to emerge as a class of appealing semiconductor materials for application in transparent electronics. In this work, a high performance bottom-gate n-type transparent thin-film transistors are reported, being the discussion primarily focused on the influence of the indium zinc oxide active layer thickness on the properties of the devices. For this purpose, transparent transistors with active layer thicknesses ranging from 15 nm to 60 nm were produced at room temperature using rf magnetron sputtering. Optical transmittance data in the visible range reveals average transmittance higher than 80\%, including the glass substrate. The devices work in the enhancement mode and exhibit excellent saturation drain currents. On-off ratios above 107 are achieved, but this value tends to be lower for devices with thicker semiconductor films, as a result of the decrease in the resistance of the channel region with increasing thickness. Channel mobilities are also quite respectable, with some devices presenting values around 40 cm2/V s, even without any annealing or other post-deposition improvement processes. Concerning the evolution of threshold voltage with the thickness, this work shows that it increases from about 3 V in thicker films up to about 10 V in the thinnest ones. The interesting electrical properties obtained and the versatility arising from the fact that it is possible to modify them changing only the thickness of the semiconductor makes this new transparent transistors quite promising for future transparent ICs. {\textcopyright} 2006 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.jnoncrysol.2006.01.067}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744780986\&partnerID=40\&md5=8525275495b8a98612da95e1efa30042}, author = {Barquinha, P., Pimentel, A., Marques, A., Pereira, L., Martins, R., Fortunato, E.} } @article {Barquinha2006319, title = {Influence of time, light and temperature on the electrical properties of zinc oxide TFTs}, journal = {Superlattices and Microstructures}, volume = {39}, number = {1-4}, year = {2006}, note = {

cited By 26

}, pages = {319-327}, abstract = {

In this work we present a study concerning the influence of some of the most important external factors on the electrical properties of transparent thin-film transistors (TFTs), using zinc oxide produced at room temperature as the semiconductor material. Electrical characterization performed sixteen months after the production of the devices showed a decrease in the on/off ratio from 8{\texttimes}105 to 1{\texttimes}105, mainly due to the increase of the off-current. We also observed a small increase in the saturation mobility, a decrease in the threshold voltage and an increase in the gate voltage swing (by factors of about 1.2, 0.9 and 1.6, respectively). Exposure to ambient light does not have a noticeable effect on the electrical properties, which is an important point as regards the application of these devices in active matrix displays. Some variation of the electrical properties was only detectable under intense white light radiation. In order to evaluate the temperature effect on the TFTs, they were also characterized at 90 {\textdegree}C. At this temperature we noticed that the off-current increased more than two times, and the other electrical properties had a small variation, returning to their initial values after cooling, meaning that the process is totally reversible. {\textcopyright} 2005 Elsevier Ltd. All rights reserved.

}, doi = {10.1016/j.spmi.2005.08.057}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-29344450647\&partnerID=40\&md5=bdc9f018528c06fc9760fe0d59bc1ccf}, author = {Barquinha, P., Fortunato, E., Gon{\c c}alves, A., Pimentel, A., Marques, A., Pereira, L., Martins, R.} } @article {Martins200613, title = {Insights on amorphous silicon nip and MIS 3D position sensitive detectors}, journal = {Materials Science Forum}, volume = {514-516}, number = {PART 1}, year = {2006}, note = {

cited By 2

}, pages = {13-17}, abstract = {

This work aims to report results of the spatial and frequency optical detection limits of integrated arrays of 32 one-dimensional amorphous silicon thin film position sensitive detectors with nip or MIS structure, under continuous and pulsed laser operation conditions. The arrays occupy a total active area of 45 mm2 and have a plane image resolution better than 15 μm with a cut-off frequency of about 6.8 kHz. The non-linearity of the array components varies with the frequency, being about 1.6\% for 200 Hz and about 4\% for the cut-off frequency (6.8 kHz).

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-37849015836\&partnerID=40\&md5=b739843d5eb7fa40c0b28a3354336ce4}, author = {Martins, R.a , Costa, D.a , {\'A}guas, H.a , Soares, F.a , Marques, A.a b , Ferreira, I.a , Borges, P.b , Pereira, S.b , Raniero, L.} } @article {{\'A}guas20061787, title = {Investigation of a-Si:H 1D MIS position sensitive detectors for application in 3D sensors}, journal = {Journal of Non-Crystalline Solids}, volume = {352}, number = {9-20 SPEC. ISS.}, year = {2006}, note = {

cited By 4

}, pages = {1787-1791}, abstract = {

This paper presents the results achieved in optimized 1D position sensitive detectors (PSD) using a metal-insulator-semiconductor (MIS) structure and different length to width ratios, in order to determine the optimal geometrical factor for the desired 3D integration. The results show that the optimized MIS PSD produced, exhibited linearity errors as low as 0.8\% and sensitivities of 32 mV/cm, for a 5 mW spot beam intensity at a wavelength of 532 nm. The sensors can achieve a longitudinal spatial resolution of 1.25 μm (estimated by modulation transfer function calculation), while the transverse resolution depends on the minimum width used for each sensor. The calculated Jones parameter of the sensors is higher than 1011 J, with a fall-off parameter of 0.012 cm-1, indicating a high signal to noise detection ratio. {\textcopyright} 2006 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.jnoncrysol.2005.09.042}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745444243\&partnerID=40\&md5=5d54f4d3e8343e8716f73a14d7bd8650}, author = {{\'A}guas, H., Pereira, L., Raniero, L., Costa, D., Fortunato, E., Martins, R.} } @conference {Raniero2005543, title = {Influence of hydrogen plasma on electrical and optical properties of transparent conductive oxides}, booktitle = {Materials Research Society Symposium Proceedings}, volume = {862}, year = {2005}, note = {

cited By 0

}, pages = {543-548}, abstract = {

In this work we study the optical and electrical behavior of ZnO:Ga, ITO and IZO films deposited on glass after sustaining different hydrogen plasma conditions and exposure times. This work was complemented by analyzing the surface morphology of the set of films, which allow us to determine the role of hydrogen plasma on the film{\textquoteright}s properties such as Hall mobility, free carrier concentration, sheet resistance, optical transmittance, figure of merit and state of the surface. Apart from that, the performances of solar cells using an intrinsic layer constituted by nanocrystalline silicon will be also presented. The data show that the electrical properties of solar cells were improved by using ZnO:Ga as front contact, allowing a high current density collection and single pin solar cells with efficiencies exceeding 11\%. {\textcopyright} 2005 Materials Research Society.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-30644469792\&partnerID=40\&md5=73948bf7714962bb18ad8ee8f1271ec1}, author = {Raniero, L., Gon{\c c}alves, A., Pimentel, A., Ferreira, I., Zhang, S., Pereira, L., {\'A}guas, H., Fortunato, E., Martins, R.} } @article {Pereira2005102, title = {Influence of metal induced crystallization parameters on the performance of polycrystalline silicon thin film transistors}, journal = {Thin Solid Films}, volume = {487}, number = {1-2}, year = {2005}, note = {

cited By 14

}, pages = {102-106}, abstract = {

In this work, metal induced crystallization using nickel was employed to obtain polycrystalline silicon by crystallization of amorphous films for thin film transistor applications. The devices were produced through only one lithographic process with a bottom gate configuration using a new gate dielectric consisting of a multi-layer of aluminum oxide/titanium oxide produced by atomic layer deposition. The best results were obtained for TFTs with the active layer of poly-Si crystallized for 20 h at 500 {\textdegree}C using a nickel layer of 0.5 nm where the effective mobility is 45.5 cm2 V-1 s-1. The threshold voltage, the on/off current ratio and the sub-threshold voltage are, respectively, 11.9 V, 5.55{\texttimes}104 and 2.49 V/dec. {\textcopyright} 2005 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.tsf.2005.01.045}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-22944482823\&partnerID=40\&md5=c443e5f82479780a6c3c621996b04144}, author = {Pereira, L., Barquinha, P., Fortunato, E., Martins, R.} } @article {Raniero2005349, title = {Influence of the layer thickness and hydrogen dilution on electrical properties of large area amorphous silicon p-i-n solar cell}, journal = {Solar Energy Materials and Solar Cells}, volume = {87}, number = {1-4}, year = {2005}, note = {

cited By 3

}, pages = {349-355}, abstract = {

The aim of this work is to present data concerning the optimization of performances of a large area amorphous silicon p-i-n solar cell (30{\texttimes}40 cm2) deposited by plasma enhanced chemical vapour deposition (PECVD) at 27.12 MHz. In this work the solar cell was split into small areas of 0.126 cm2, aiming to study the device performance uniformity, where emphasis was put on the role of the n-layer thickness. The solar cells were studied through the spectral response behaviour in the 400-750 nm range as well as by the behaviour of the AC impedance. Solar cells with fill factor of 0.58, open circuit voltage of 0.83 V, short circuit current density of 17.14 mA/cm2 and an efficiency of 8\% were obtained at growth rates higher than 0.3 nm/s. {\textcopyright} 2004 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.solmat.2004.08.014}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-17644411994\&partnerID=40\&md5=24b3843ee56a6e1dcd85bdee2d2a7b67}, author = {Raniero, L., Martins, N., Canhola, P., Zhang, S., Pereira, S., Ferreira, I., Fortunato, E., Martins, R.} } @article {Pereira2005210, title = {Influence of the oxygen/argon ratio on the properties of sputtered hafnium oxide}, journal = {Materials Science and Engineering B: Solid-State Materials for Advanced Technology}, volume = {118}, number = {1-3}, year = {2005}, note = {

cited By 44

}, pages = {210-213}, abstract = {

In this work we have focused our attention on the role of the gas mixture (O2/Ar) used during HfO2 thin film processing by r.f. magnetron sputtering, to produce dielectrics with suitable characteristics to be used as gate dielectric. Increasing the O2/Ar ratio from 0 to 0.2, the films properties (optical gap, permittivity, resistivity and compactness) are improved. At these conditions, films with a band gap around 5 eV were produced, indicating a good stoichiometry. Also the flat band voltage has a reduction of almost three times indicating also a reduction of the same order on the fixed charge density at the semiconductor-insulator interface. The dielectric constant is around 16 which is very good, since the surface of the silicon where the HfO2 films were deposited contains a SiO 2 layer of about 3 nm that gives an effective dielectric constant above 20, close to the HfO2 stoichiometric value (\~{}25). Further increase on the O2/Ar ratio does not produce significant improvements. {\textcopyright} 2004 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.mseb.2004.12.030}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-15344339242\&partnerID=40\&md5=dc4fa9092a6a0017715d3aedf3135a4f}, author = {Pereira, L., Barquinha, P., Fortunato, E., Martins, R.} } @article {Barquinha2004243, title = {Influence of the deposition conditions on the properties of titanium oxide produced by r.f. magnetron sputtering}, journal = {Materials Science in Semiconductor Processing}, volume = {7}, number = {4-6 SPEC. ISS.}, year = {2004}, note = {

cited By 13

}, pages = {243-247}, abstract = {

This work refers to the electro-optical and structural characteristics of titanium oxide (TiOx) thin films produced by radio frequency (r.f.) magnetron sputtering that present promising performances for gate dielectric applications, alone or in mixed tandem structures, such as with Al yOz films, taking advantage of its high dielectric constant. Films produced with a O2/Ar ratio between 0.1 and 0.15 present an improved stochiometry and density where the resistivity overcomes 1011 Ω cm and the fixed charge density decreases below 10 12 cm-2. The deposition pressure influences greatly the growth rate that seems to be a determinant factor dictating the films properties. {\textcopyright} 2004 Elsevier Ltd. All rights reserved.

}, doi = {10.1016/j.mssp.2004.09.116}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-9544232544\&partnerID=40\&md5=08955064e13e1daa1473051f69d00b43}, author = {Barquinha, P., Pereira, L., {\'A}guas, H., Fortunato, E., Martins, R.} } @article {Nedev2004108, title = {Influence of the rapid thermal annealing on the properties of thin a-Si films}, journal = {Materials Science Forum}, volume = {455-456}, year = {2004}, note = {

cited By 0

}, pages = {108-111}, abstract = {

The variation of the structure, morphology and the electrical properties of thin amorphous silicon films caused by Rapid Thermal Annealing is studied. The films annealed at 1200{\textdegree}C for 2 minutes change their structure to polycrystalline and as a result their resistivity decreases by 4 orders of magnitude. Due to the small thickness of the as deposited amorphous silicon the obtained poly-Si is strongly irregular and has many discontinuities in its texture.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-3142658011\&partnerID=40\&md5=a51bb9a36b0e33a7e17d6cdc2ea5c9e1}, author = {Nedev, N.a b , Beshkov, G.a , Fortunato, E.b , Georgiev, S.S.a b , Ivanov, T.a , Raniero, L.b , Zhang, S.b c , Martins, R.b} } @article {Assun{\c c}{\~a}o2003401, title = {Influence of the deposition pressure on the properties of transparent and conductive ZnO:Ga thin-film produced by r.f. sputtering at room temperature}, journal = {Thin Solid Films}, volume = {427}, number = {1-2}, year = {2003}, note = {

cited By 231

}, pages = {401-405}, abstract = {

Highly conducting and transparent gallium doped zinc oxide thin films have been deposited at high growth rates by r.f. magnetron sputtering at room temperature on inexpensive soda lime glass substrates. The argon sputtering pressure was varied between 0.15 and 2.1 Pa. The lowest resistivity was 2.6 {\texttimes} 10-4 Ω cm (sheet resistance ≈6 Ω/sq. for a thickness ≈600 nm) and was obtained at an argon sputtering pressure of 0.15 Pa and a r.f. power of 175 W. The films present an overall transmittance in the visible spectra of approximately 90\%. The increase on the resistivity for higher sputtering pressures is due to a decrease of both, mobility and carrier concentration, and is associated to a change on the surface morphology. The low resistivity, accomplished with a high growth rate (290 {\r A}/min) and with a room temperature deposition enables these films deposition onto polymeric substrates for flexible optoelectronic devices. {\textcopyright} 2002 Elsevier Science B.V. All rights reserved.

}, doi = {10.1016/S0040-6090(02)01184-7}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037416605\&partnerID=40\&md5=63176f58a8de9bde447957a7e36cd3ba}, author = {Assun{\c c}{\~a}o, V.a , Fortunato, E.a , Marques, A.a , {\'A}guas, H.a , Ferreira, I.a , Costa, M.E.V.b , Martins, R.a} } @article {{\'A}guas2002387, title = {Influence of a DC grid on silane r.f. plasma properties}, journal = {Vacuum}, volume = {64}, number = {3-4}, year = {2002}, note = {

cited By 2

}, pages = {387-392}, abstract = {

In this work we show that it is possible to control the plasma regime in the region close to the substrate in r.f. silane discharges. The PECVD reactor works in a modified triode configuration, where the control over the plasma regime is performed by polarising a grid electrode, placed close to the r.f. electrode, with a DC power source. Besides that, the DC grid allows also to control the energy of the ion bombardment, because the plasma potential will be a function of the voltage (Vpol) applied to the DC grid. The silane plasma was characterised with a Langmuir probe and an impedance probe. We were able to identify three plasma regimes in the region close to the substrate: γ' regime for Vpol\<0 V; γ'-α regime for 0 V\<Vpol\<40 V; and α regime for Vpol40 V. The γ' regime is associated with a high concentration of dust particles in plasma and high electron energy (≈8eV), while the α regime is associated with a free dust plasma and low electron energy (≈2eV). The intermediate regime, γ'-α, is characterised by the presence of smaller particles (≈2-5nm) that can be beneficial for the film{\textquoteright}s properties. {\textcopyright} 2002 Elsevier Science Ltd. All rights reserved.

}, doi = {10.1016/S0042-207X(01)00343-8}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036136012\&partnerID=40\&md5=fdbc699fbf0bf7299f825847f61b230c}, author = {{\'A}guas, H., Fortunato, E., Martins, R.} } @article {Ferreira2002591, title = {Influence of hydrogen gas dilution on the properties of silicon-doped thin films prepared by the hot-wire plasma-assisted technique}, journal = {Key Engineering Materials}, volume = {230-232}, year = {2002}, note = {

cited By 0

}, pages = {591-594}, abstract = {

P- and n-type silicon thin films have been produced using a new hot wire plasma assisted deposition process that combines the conventional plasma enhanced chemical vapor deposition and the hot wire techniques. The films were produced in the presence of different hydrogen gas flow and their optoelectronic, structural and compositional properties have been studied. The optimized optoelectronic results achieved for n-type Si:H films are conductivity at room temperature of 9.4(Ωcm)-1 and optical band gap of 2eV while for p-type SiC:H films these values are 1 {\texttimes} 10-2(Ωcm)-1 and 1.6eV, respectively. The films exhibit the required optoelectronic characteristics and compactness for device applications such as solar cells.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036434960\&partnerID=40\&md5=680eabba156e5241216387c48e230358}, author = {Ferreira, I., Vilarinho, P., Fernandes, F., Fortunato, E., Martins, R.} } @article {Fantoni2002151, title = {Influence of the intrinsic layer characteristics on a-Si:H p-i-n solar cell performance analysed by means of a computer simulation}, journal = {Solar Energy Materials and Solar Cells}, volume = {73}, number = {2}, year = {2002}, note = {

cited By 20

}, pages = {151-162}, abstract = {

In this paper a set of one-dimensional simulations of a-Si:H p-i-n junctions under different illumination conditions and with different intrinsic layer are presented. The simulation program ASCA permits the analysis of the internal electrical behaviour of the cell allowing a comparison among the different internal configurations determined by a change in the input set. Results about the internal electric configuration will be presented and discussed outlining their influence on the current tension characteristic curve. Considerations about the drift-diffusion and the generation-recombination balance distributions, outlined by the simulation, can be used to explain the correlation between the basic device output, the i-layer characteristics (thickness and DOS), the incident radiation intensity and photon energy. {\textcopyright} 2002 Elsevier Science B.V. All rights reserved.

}, doi = {10.1016/S0927-0248(01)00120-9}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036605126\&partnerID=40\&md5=a4be0908ef11a190a7bc219046e9412f}, author = {Fantoni, A.a b , Viera, M.a , Martins, R.b} } @article {{\'A}guas2002583, title = {Influence of the plasma regime on the structural, optical and transport properties of a-Si:H thin films}, journal = {Key Engineering Materials}, volume = {230-232}, year = {2002}, note = {

cited By 0

}, pages = {583-586}, abstract = {

In this work we show that it is possible to control the plasma species present near the substrate surface, from what is usually associated with an α regime (a plasma free of particles) to a γ{\textquoteright} regime (a plasma where particles are present) and simultaneously control the energy of the ions striking the substrate during a-Si:H deposition from a silane glow discharge in a modified triode (MT) type PECVD reactor, where a DC mesh electrode biased with Vpol is located in front of the r.f electrode. The presence of large particles in the plasma leads to the deposition of the films with the poorest optoelectronic properties. When the particle size in the plasma decrease the film properties improve, but, when particles are no longer present in the plasma region close to the substrate, like in a α like regime, the properties of the films deteriorate again. The results show that the best transport properties are achieved for the films deposited in the α-γ{\textquoteright} transition regime corresponding to 0V\<Vpol\<51V. Under this condition the films present a dark conductivity, σ d ≈ 10-11 (Ωcm)-1, photosensitivity, S ≈ 107, activation energy, ΔE ≈ 0.9 eV, hydrogen content, CH ≈ 10\%, factor of microstructure, R ≈ 0.085 and an optical gap, Eop ≈ 1.77 eV.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036436562\&partnerID=40\&md5=2732b40d068ebcd3cc9670443d94695e}, author = {{\'A}guas, H., Martins, R., Fortunato, E.} } @article {Fortunato2002610, title = {Influence of the strain on the electrical resistance of zinc oxide doped thin film deposited on polymer substrates}, journal = {Advanced Engineering Materials}, volume = {4}, number = {8}, year = {2002}, note = {

cited By 21

}, pages = {610-612}, abstract = {

Tensile tests were performed on PET films coated with Al doped zinc oxide films by RF magnetron sputtering. During the tensile elongation, the electrical resistance of the oxide was evaluated in situ. The results indicate that the increase in the electrical resistance is related to the crack debsity and crack width, which also depends on the film thickness.

}, doi = {10.1002/1527-2648(20020806)4:8<610::AID-ADEM610>3.0.CO;2-1}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036671534\&partnerID=40\&md5=c9a1a7d9d7e3b9a0f6321b7986abdb2c}, author = {Fortunato, E.a , Nunes, P.a , Marques, A.a , Costa, D.a , {\'A}guas, H.a , Ferreira, I.a , Costa, M.E.V.b , Godinho, M.H.a , Almeida} } @article {Nunes20011125, title = {Influence of the annealing conditions on the properties of ZnO thin films}, journal = {International Journal of Inorganic Materials}, volume = {3}, number = {8}, year = {2001}, note = {

cited By 52

}, pages = {1125-1128}, abstract = {

The effect of annealing treatment (in the presence of different types of atmospheres) on the performances of zinc oxide thin films (intrinsic and doped with In and Al) prepared by spray pyrolysis have been studied, with the aim to determine more adequate conditions to improve the properties of the films. The results show that the annealing treatment leads to substantial changes in the structural, electrical and optical characteristics of ZnO thin films. The most significant improvements were obtained after annealing in forming gas (reduction atmosphere) at 200{\textdegree}C during 2 h. The ZnO:In film after heat treatment was the one that exhibited the lowest resistivity (p=5.2x10-2 ωcm) and a high transmittance (T=86\%). {\textcopyright} 2001 Elsevier Science Ltd. All rights reserved.

}, doi = {10.1016/S1466-6049(01)00113-1}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035208404\&partnerID=40\&md5=2e96a43682da913cb765146a0d72fb08}, author = {Nunes, P., Fortunato, E., Martins, R.} } @article {Nunes20011129, title = {Influence of the deposition conditions on the gas sensitivity of zinc oxide thin films deposited by spray pyrolysis}, journal = {International Journal of Inorganic Materials}, volume = {3}, number = {8}, year = {2001}, note = {

cited By 50

}, pages = {1129-1131}, abstract = {

In this work we present preliminary results on the sensitivity to methane gas of zinc oxide thin films deposited by spray pyrolysis. It was found that using highly resistive (above 104 Ω cm) thin films and by performing the measurements at 200{\textdegree}C a sensitivity better than one order of magnitude was found to detect 2000 ppm of methane. A linear dependence on the sensitivity between 100 and 2000 ppm of methane was also obtained. {\textcopyright} 2001 Elsevier Science Ltd. All rights reserved.

}, doi = {10.1016/S1466-6049(01)00136-2}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035208286\&partnerID=40\&md5=9aa84ec636f148d08ce6d83cb02d346f}, author = {Nunes, P., Fortunato, E., Lopes, A., Martins, R.} } @article {{\'A}guas200111, title = {Influence of the plasma regime on the structural, optical, electrical and morphological properties of a-Si:H thin films}, journal = {Materials Science Forum}, volume = {382}, year = {2001}, note = {

cited By 3

}, pages = {11-20}, abstract = {

{In this work we report how it is possible to control the plasma regime near the substrate surface, from predominantly α to predominantly γ{\textquoteright}, passing trough and intermediate α-γ{\textquoteright} regime, and simultaneously control the energy of the ions striking the substrate during a-Si:H deposition from a silane glow discharge in a modified triode type PECVD reactor. To do so, we apply a DC voltage (Vpol to a set of grids placed in front of the r.f. electrode and by doing this, we control the energy of the ions striking the substrate during the film{\textquoteright}s growth and the plasma regime near the substrate. Under a plasma of the γ{\textquoteright} regime, the surface roughness is high and the films are poorly compact. In the α-γ{\textquoteright} regime, the ion bombardment is moderate and the films are highly smooth and compact. In the α regime the ion bombardment is higher and so the films can become more compact but the surface roughness increases and the electrical properties deteriorate. The results achieved show that the best transport properties are achieved for the films deposited in the α-γ{\textquoteright} regime corresponding to a Vpol of 38 V. Under this condition the films presented a dark conductivity, σd = 6.2{\texttimes}10-12 (Ωcm)-1, activation energy, ΔE ≈ 0.9 eV, hydrogen content

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035682789\&partnerID=40\&md5=91718c4ebd3a1dc5162c1fafa64aea93}, author = {{\'A}guas, H., Martins, R., Nunes, Y., Maneira, M., Fortunato, E.} } @article {Nunes2001277, title = {Influence of the post-treatment on the properties of ZnO thin films}, journal = {Thin Solid Films}, volume = {383}, number = {1-2}, year = {2001}, note = {

cited By 157

}, pages = {277-280}, abstract = {

In this work a study of the influence of the annealing treatment (atmosphere and temperature) on the properties of zinc oxide thin films (intrinsic and doped with indium and aluminum) prepared by spray pyrolysis is presented. The result shows that the type of atmosphere (reduction or oxidant) has an important role in the changes observed in the structural, electrical and optical properties of the ZnO thin films. The ZnO thin film doped with indium, presents the lowest resistivity (ρ = 5.8{\texttimes}10-3 Ωcm) associated to a high transmittance (T = 86\%), characteristics required for application on optoelectronic devices.

}, doi = {10.1016/S0040-6090(00)01577-7}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035246835\&partnerID=40\&md5=b6fef2a67cc9d2aa0f45b48be8a02d4e}, author = {Nunes, P., Fortunato, E., Martins, R.} } @article {Ba{\'\i}a2001244, title = {Influence of the process parameters on structural and electrical properties of r.f. magnetron sputtering ITO films}, journal = {Thin Solid Films}, volume = {383}, number = {1-2}, year = {2001}, note = {

cited By 26

}, pages = {244-247}, abstract = {

This paper presents results of the role of the oxygen concentration (CO) and the deposition pressure (pd) on structural and electrical properties of indium tin oxide films produced by r.f. magnetron sputtering. The films were annealed in air, followed by a reannealed stage in hydrogen, aiming to improve the film{\textquoteright}s transparency and conductivity. The results achieved show that the films texture grain size, structure and compactness is more influenced by CO than by pd, the same does not happen with the electrical properties.

}, doi = {10.1016/S0040-6090(00)01589-3}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-2942746184\&partnerID=40\&md5=bfd887999ac9907260e9597310027833}, author = {Ba{\'\i}a, I., Fernandes, B., Nunes, P., Quintela, M., Martins, R.} } @article {Martins20001094, title = {Improvement of a-Si:H device stability and performances by proper design of the interfaces}, journal = {Journal of Non-Crystalline Solids}, volume = {266-269 B}, year = {2000}, note = {

cited By 6

}, pages = {1094-1098}, abstract = {

This paper deals with a new design method for the interfaces of a-Si:H pin solar cells that improves the stability and performances of devices deposited in a single batch chamber process. The method consists in removing a deposited sacrificial layer placed between the p/i and/or i/n interfaces by etching. This layer is an absorber of defects and impurities that are introduced in the interfaces, mainly from the chamber walls cross-contamination and the substrate surface. The results achieved increase the device fill factor and short circuit current density, respectively towards 75\% and 16.3 mA cm-2, with a final efficiency of about 10\%, before light soaking experiments. {\textcopyright} 2000 Elsevier Science B.V. All rights reserved.

}, doi = {10.1016/S0022-3093(99)00909-6}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0007246306\&partnerID=40\&md5=e7fcbcb5287125fa7f583fd30e4a5f77}, author = {Martins, R., Ferreira, I., Cabrita, A., Fortunato, E.} } @article {Nunes199945, title = {Influence of the doping and annealing atmosphere on zinc oxide thin films deposited by spray pyrolysis}, journal = {Vacuum}, volume = {52}, number = {1-2}, year = {1999}, note = {

cited By 58

}, pages = {45-49}, abstract = {

Undoped and doped (indium and aluminium) zinc oxide (ZnO) thin films have been prepared by spray pyrolysis, and the effect of the doping and annealing atmosphere on the electrical, optical and structural properties of the produced films has been investigated. The deposited films have a high resistivity. Annealing the films in an argon atmosphere or under vacuum leads to a substantial reduction of the electrical resistivity of the films and to an increase on the degree of cristallinity of the deposited material. The most pronounced changes were observed in the films annealed in Argon. The results also indicate that doping highly influences the electrical and structural properties of the films, which is more pronounced in the films doped with Indium. {\textcopyright} 1998 Elsevier Science Ltd. All rights reserved.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032777967\&partnerID=40\&md5=1a1a61ffda881e1da92bb4fafd5d9fe8}, author = {Nunes, P.a , Malik, A.a , Fernandes, B.a , Fortunato, E.a , Vilarinho, P.b , Martins, R.a} } @conference {Ferreira1999831, title = {Influence of the H2 dilution and filament temperature on the properties of P doped silicon carbide thin films produced by hot-wire technique}, booktitle = {Materials Research Society Symposium - Proceedings}, volume = {507}, year = {1999}, note = {

cited By 1

}, pages = {831-836}, abstract = {

This work deals with the role of hydrogen dilution and filament temperature on the morphology, structure and electrical properties of nanocrystalline boron doped silicon carbide thin films produced by hot-wire technique. The structural and morphological data obtained by XRD, SEM and micro-Raman show that for filament temperatures and hydrogen dilutions above 2100 {\textdegree}C and 90\%, respectively, the surface morphology of the films is granular with a needle shape, while for lower filament temperatures and hydrogen dilutions the surface morphology gets honeycomb like. The SIMS analysis reveals that films produced with filament temperatures of about 2200 {\textdegree}C and hydrogen dilution of 99\% present a higher hydrogen and carbon incorporation than the films produced at lower temperatures and hydrogen dilutions. These results agree with the electrical and optical characteristics recorded that show that the films produced exhibit optical gaps in the range from 1.8 to 2 eV and transverse conductivities ranging from 10-1 S/cm to 10-3 S/cm, consistent with the degree of films crystallinity and carbon incorporation recorded.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032678424\&partnerID=40\&md5=81996dc8d0f5fec657735b6a59067cc5}, author = {Ferreira, I., Aguas, H., Mendes, L., Fernandes, F., Fortunato, E., Martins, R.} } @article {Martins1998144, title = {Investigation of the amorphous to microcrystalline phase transition of thin film silicon produced by PECVD}, journal = {Thin Solid Films}, volume = {317}, number = {1-2}, year = {1998}, note = {

cited By 9

}, pages = {144-148}, abstract = {

We have deposited by Plasma Enhanced Chemical Vapour Deposition phosphorus doped amorphous and microcrystalline silicon films, as a function of the RF power (10-300 W), using a PH3/(SiH4 + H2 + He)mixture. It was found that films microcrystallization occurs for powers above 130 W, where a clear phase transition occurs. The microcrystalline films produced present high dark conductivities and optical band gaps, where the crystalline volume fraction is above 25\%, as revealed by micro Raman spectroscopy. The Hall mobility have been also determined for amorphous and microcrystalline films, as a function of temperature, in the range 280-340 K. The data show that for the microcrystalline films the conduction is mainly in the extended states of the microcrystals, confirming also the double sign anomaly. That is, for n-type films, the sign is positive for the amorphous case while it is negative for the microcrystalline case. {\textcopyright} 1998 Elsevier Science S.A.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032048851\&partnerID=40\&md5=560bdeecd60a2fe9ddb0c139457ce7e4}, author = {Martins, R.a b , Ma{\c c}arico, A.a b , Ferreira, I.a b , Nunes, R.a b , Bicho, A.a b , Fortunato, E.a b} } @conference {Lavareda199659, title = {Improved a-Si:H TFT performance using a-Six-Ni1-x/a-SixC1-x stack dielectrics}, booktitle = {Materials Research Society Symposium - Proceedings}, volume = {424}, year = {1996}, note = {

cited By 1

}, pages = {59-64}, abstract = {

In this paper we present a study on the electrical characteristics (conductivity, σ and relative dielectric constant, εr) of amorphous silicon nitride (a-SixN1-x) and carbide (a-SixC1-x) films deposited by PECVD, used as dielectric materials in TFT devices, aiming to select the most adequate alloy that lead to improve device performances. Besides that, double stack a-SixN1-x/a-SixC1-x structures were developed and applied as dielectric layers on TFTs, whose performances show to be superior to those ones using single silicon nitride or silicon carbide as dielectric.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030399823\&partnerID=40\&md5=4e4eecf30f5c81dd94a29596a1017d06}, author = {Lavareda, G., Fortunato, E., Carvalho, C.Nunes, Martins, R.} } @conference {NunesdeCarvalho1996861, title = {Improvement of the ITO-p interface in a-Si:H solar cells using a thin SiO intermediate layer}, booktitle = {Materials Research Society Symposium - Proceedings}, volume = {420}, year = {1996}, note = {

cited By 1

}, pages = {861-865}, abstract = {

The use of ITO thin films on glass/ITO/p-i-n/metal amorphous silicon solar cells is reviewed. It is suggested a new application for silicon monoxide thin films on the ITO-p interface, as an intermediate layer, to minimize the ITO thin film deterioration process, during the early stage of exposure to a silane plasma rich in hydrogen. The thickness of the silicon monoxide thin films is chosen not to worsen the optical and electrical properties of the ITO thin films. The ITO-p interface is optimized (due to impurities diffusion decrease), leading to an overall improvement of the device performance.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030407693\&partnerID=40\&md5=36f09248d418819f380bd5c995d8d881}, author = {Nunes de Carvalho, C., de Nijs, J.M.M., Ferreira, I., Fortunato, E., Martins, R.} } @conference {deCarvalho199625, title = {Improvement of the ITO-P interface in a-Si:H solar cells using a thin SiO intermediate layer}, booktitle = {Materials Research Society Symposium - Proceedings}, volume = {426}, year = {1996}, note = {

cited By 0

}, pages = {25-29}, abstract = {

The use of ITO films on glass/ITO/p-i-n/metal amorphous silicon solar cells is reviewed. It is suggested a new application for silicon monoxide thin films on the ITO-p interface, as an intermediate layer, to minimize the ITO thin film deterioration process, during the early stage of exposure to a silane plasma rich in hydrogen. The thickness of the silicon monoxide thin films is chosen not to worsen the optical and electrical properties of the ITO thin films. The ITO-p interface is optimized (due to impurities diffusion decrease), leading to an overall improvement of the device performance.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030380927\&partnerID=40\&md5=e78c732740cf51a4a3acd6773ef1ac4d}, author = {de Carvalho, C.Nunes, de Nijs, J.M.M., Ferreira, I., Fortunato, E., Martins, R.} } @article {Martins19962143, title = {Interpretation of the static and dynamic characteristics of 1-D thin film position sensitive detectors based on a-Si:H p-i-n Diodes}, journal = {IEEE Transactions on Electron Devices}, volume = {43}, number = {12}, year = {1996}, note = {

cited By 7

}, pages = {2143-2152}, abstract = {

In this work, we present a model to interpret the steady-state and the dynamic detection limits of 1-D Thin Film Position Sensitive Detectors (1-D TFPSD) based on p-i-n a-Si:H devices. From this, an equivalent electric circuit is derived and the predicted values are compared with the experimental results obtained in 1-D TFPSD devices, with different sizes. The model is also able to determine the device characteristics that influence the spatial limits and the response time of the device. {\textcopyright} 1996 IEEE.

}, doi = {10.1109/16.544385}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030379338\&partnerID=40\&md5=ccecaf09a3766c27fcb1cd1beab43793}, author = {Martins, R.F.P., Fortunato, E.M.C.} } @article {Vieira19941109, title = {Influence of photodegradation on the υτ and microstructure of pin a-Si:H devices}, journal = {Vacuum}, volume = {45}, number = {10-11}, year = {1994}, note = {

cited By 0

}, pages = {1109-1111}, abstract = {

Pin solar cells of a-Si:H were light soaked. The cell characteristics, the optoelectronic properties and the microstructure parameter, as well as the hydrogen content and density of states of the i-layer, were monitored throughout the entire light-induced degradation process and compared with the corresponding μτ product (for both carriers) inferred through steady photoconductivity and FST measurements. Results suggest a correlation between the decrease of μτ product for electrons and the increase of the fraction of hydrogen bonded on internal surfaces, showing structural changes during the degradation process. {\textcopyright} 1994.

}, doi = {10.1016/0042-207X(94)90037-X}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028516523\&partnerID=40\&md5=5a1957c989300a417d847bb77d88e115}, author = {Vieira, M., Fortunato, E., Carvalho, C., Lavareda, G., Martins, R.} } @article {Martins19839, title = {The interpretation of the electric and optical properties of a-Si:H films produced by rf glow discharge through dark conductivity, photoconductivity and pulse controlled capacitance-voltage measurements}, journal = {Journal of Non-Crystalline Solids}, volume = {57}, number = {1}, year = {1983}, note = {

cited By 0

}, pages = {9-22}, abstract = {

This paper deals with the interpretation of transport properties of amorphous silicon hydrogenated films (a-Si:H) through dark conductivity, photoconductivity and pulse controlled capacitance-voltage measurements. a-Si:H films were produced by rf glow discharge coupled either inductively or capacitively to a 3\% SiH4/Ar mixture at different crossed electromagnetic static fields. The data concerned with the dark activation energy, photoactivation energy, variation of the density of localized states and photosensitivity, (σph/σd)25{\textdegree}C, of a-Si:H films can account for their optoelectronic properties which are strongly dependent on the deposition parameters. We also observed that crossed electromagnetic static fields applied during film formation influences hydrogen incorporation in a different manner than previously proposed. {\textcopyright} 1983.

}, doi = {10.1016/0022-3093(83)90404-0}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020807008\&partnerID=40\&md5=1807d96fc8f9c108f34290a029959a49}, author = {Martins, R., Dias, A.G., Guimar{\~a}es, L.} }