@article {Lorenz2016, title = {The 2016 oxide electronic materials and oxide interfaces roadmap}, journal = {Journal of Physics D: Applied Physics}, volume = {49}, number = {43}, year = {2016}, note = {

cited By 0

}, abstract = {

Oxide electronic materials provide a plethora of possible applications and offer ample opportunity for scientists to probe into some of the exciting and intriguing phenomena exhibited by oxide systems and oxide interfaces. In addition to the already diverse spectrum of properties, the nanoscale form of oxides provides a new dimension of hitherto unknown phenomena due to the increased surface-to-volume ratio. Oxide electronic materials are becoming increasingly important in a wide range of applications including transparent electronics, optoelectronics, magnetoelectronics, photonics, spintronics, thermoelectrics, piezoelectrics, power harvesting, hydrogen storage and environmental waste management. Synthesis and fabrication of these materials, as well as processing into particular device structures to suit a specific application is still a challenge. Further, characterization of these materials to understand the tunability of their properties and the novel properties that evolve due to their nanostructured nature is another facet of the challenge. The research related to the oxide electronic field is at an impressionable stage, and this has motivated us to contribute with a roadmap on {\textquoteright}oxide electronic materials and oxide interfaces{\textquoteright}. This roadmap envisages the potential applications of oxide materials in cutting edge technologies and focuses on the necessary advances required to implement these materials, including both conventional and novel techniques for the synthesis, characterization, processing and fabrication of nanostructured oxides and oxide-based devices. The contents of this roadmap will highlight the functional and correlated properties of oxides in bulk, nano, thin film, multilayer and heterostructure forms, as well as the theoretical considerations behind both present and future applications in many technologically important areas as pointed out by Venkatesan. The contributions in this roadmap span several thematic groups which are represented by the following authors: novel field effect transistors and bipolar devices by Fortunato, Grundmann, Boschker, Rao, and Rogers; energy conversion and saving by Zaban, Weidenkaff, and Murakami; new opportunities of photonics by Fompeyrine, and Zuniga-Perez; multiferroic materials including novel phenomena by Ramesh, Spaldin, Mertig, Lorenz, Srinivasan, and Prellier; and concepts for topological oxide electronics by Kawasaki, Pentcheva, and Gegenwart. Finally, Miletto Granozio presents the European action {\textquoteright}towards oxide-based electronics{\textquoteright} which develops an oxide electronics roadmap with emphasis on future nonvolatile memories and the required technologies. In summary, we do hope that this oxide roadmap appears as an interesting up-to-date snapshot on one of the most exciting and active areas of solid state physics, materials science, and chemistry, which even after many years of very successful development shows in short intervals novel insights and achievements. Guest editors: M S Ramachandra Rao and Michael Lorenz. {\textcopyright} 2016 IOP Publishing Ltd.

}, doi = {10.1088/0022-3727/49/43/433001}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992395868\&partnerID=40\&md5=c4c21b5579a87a37f490b2b1f349931f}, author = {Lorenz, M.a , Ramachandra Rao, M.S.b , Venkatesan, T.c , Fortunato, E.d , Barquinha, P.d , Branquinho, R.d , Salgueiro, D.d , Ma} } @article {Liu2016, title = {Hole mobility modulation of solution-processed nickel oxide thin-film transistor based on high-k dielectric}, journal = {Applied Physics Letters}, volume = {108}, number = {23}, year = {2016}, note = {

cited By 0

}, abstract = {

Solution-processed p-type oxide semiconductors have recently attracted increasing interests for the applications in low-cost optoelectronic devices and low-power consumption complementary metal-oxide-semiconductor circuits. In this work, p-type nickel oxide (NiOx) thin films were prepared using low-temperature solution process and integrated as the channel layer in thin-film transistors (TFTs). The electrical properties of NiOx TFTs, together with the characteristics of NiOx thin films, were systematically investigated as a function of annealing temperature. By introducing aqueous high-k aluminum oxide (Al2O3) gate dielectric, the electrical performance of NiOx TFT was improved significantly compared with those based on SiO2 dielectric. Particularly, the hole mobility was found to be 60 times enhancement, quantitatively from 0.07 to 4.4 cm2/V s, which is mainly beneficial from the high areal capacitance of the Al2O3 dielectric and high-quality NiOx/Al2O3 interface. This simple solution-based method for producing p-type oxide TFTs is promising for next-generation oxide-based electronic applications. {\textcopyright} 2016 Author(s).

}, doi = {10.1063/1.4953460}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84974623209\&partnerID=40\&md5=5175cf435ed8257a8148ba904ce90163}, author = {Liu, A.a b c , Liu, G.a b c , Zhu, H.a b c , Shin, B.d , Fortunato, E.e , Martins, R.e , Shan, F.a b c} } @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 {Liu2016, title = {Solution-Processed Alkaline Lithium Oxide Dielectrics for Applications in n- and p-Type Thin-Film Transistors}, journal = {Advanced Electronic Materials}, volume = {2}, number = {9}, year = {2016}, note = {

cited By 0

}, abstract = {

High-k alkaline lithium oxide (LiOx) thin films are fabricated by spin-coating method. The LiOx thin films are annealed at different temperatures and characterized by various techniques. An optimized LiOx dielectric is achieved at an annealing temperature of 300 {\textdegree}C and exhibits wide bandgap of ≈5.5 eV, smooth surface, relatively permittivity of ≈6.7, and low leakage current density. The as-fabricated LiOx thin films are integrated, as gate dielectrics, in both n-channel indium oxide (In2O3) and p-channel cupric oxide (CuO) transistors. The optimized In2O3/LiOx thin-film transistor (TFT) exhibits high performance and high stability, such as Ion/Ioff of 107, electron mobility of 5.69 cm2 V-1 s-1, subthreshold swing of 70 mV dec-1, negligible hysteresis, and threshold voltage shift of 0.1 V under bias stress for 1.5 h. Meanwhile, the p-channel CuO TFT based on LiOx dielectric shows high Ion/Ioff of 105 and hole mobility of 1.72 cm2 V-1 s-1. All the electrical performances are achieved at an ultra-low operating voltage of 2 V. Considering the simple procedure, the moderate annealing temperature, and the low power consumption merits, these outstanding characteristics represent a significant advance toward the development of battery compatible and portable electronics. {\textcopyright} 2016 WILEY-VCH Verlag GmbH \& Co. KGaA, Weinheim

}, doi = {10.1002/aelm.201600140}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978872985\&partnerID=40\&md5=4aa037be9fb7e08f7c4b9f1de20ecc93}, author = {Liu, A.a b c , Liu, G.a b c , Zhu, C.a b c , Zhu, H.a b c , Fortunato, E.d , Martins, R.d , Shan, F.a b c} } @article {Liu2015, title = {Low-Temperature, Nontoxic Water-Induced Metal-Oxide Thin Films and Their Application in Thin-Film Transistors}, journal = {Advanced Functional Materials}, year = {2015}, note = {

cited By 4; Article in Press

}, abstract = {

Here, a simple, nontoxic, and inexpensive "water-inducement" technique for the fabrication of oxide thin films at low annealing temperatures is reported. For water-induced (WI) precursor solution, the solvent is composed of water without additional organic additives and catalysts. The thermogravimetric analysis indicates that the annealing temperature can be lowered by prolonging the annealing time. A systematic study is carried out to reveal the annealing condition dependence on the performance of the thin-film transistors (TFTs). The WI indium-zinc oxide (IZO) TFT integrated on SiO2 dielectric, annealed at 300 {\textdegree}C for 2 h, exhibits a saturation mobility of 3.35 cm2 V-1 s-1 and an on-to-off current ratio of ≈108. Interestingly, through prolonging the annealing time to 4 h, the electrical parameters of IZO TFTs annealed at 230 {\textdegree}C are comparable with the TFTs annealed at 300 {\textdegree}C. Finally, fully WI IZO TFT based on YOx dielectric is integrated and investigated. This TFT device can be regarded as "green electronics" in a true sense, because no organic-related additives are used during the whole device fabrication process. The as-fabricated IZO/YOx TFT exhibits excellent electron transport characteristics with low operating voltage (≈1.5 V), small subthreshold swing voltage of 65 mV dec-1 and the mobility in excess of 25 cm2 V-1 s-1. {\textcopyright} 2015 WILEY-VCH Verlag GmbH \& Co. KGaA, Weinheim.

}, doi = {10.1002/adfm.201500056}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926433781\&partnerID=40\&md5=8e7f711ea425ac91758ed11ead3b66e5}, author = {Liu, G.a , Liu, A.a , Zhu, H.a , Shin, B.b , Fortunato, E.c , Martins, R.c , Wang, Y.a , Shan, F.a} } @article {Lyubchyk201525, title = {Nanocrystalline thin film silicon solar cells: A deeper look into p/i interface formation}, journal = {Thin Solid Films}, volume = {591}, year = {2015}, note = {

cited By 1

}, pages = {25-31}, abstract = {

The p/i interface plays a major role in the conversion efficiency of nanocrystalline silicon (nc-Si:H) solar cells. Under plasma-enhanced chemical vapor deposition (PECVD) of the intrinsic (i) nc-Si:H layer, ion bombardment can severely affect the underlying p-doped layer and degrade the solar cell performance. The core of the present work is to investigate the effect of light and heavy ion bombardment on the structural modifications of the p-layer during the p/i interface formation. The properties of the nc-Si:H materials deposited under distinct conditions are analyzed and correlated to the deposition rate and the resulting cell efficiency. To recreate the ion bombardment during the initial stages of the i-layer deposition on the p-layer, hydrogen plasma treatment was performed for 30 s (light ion bombardment), after which a flux of silane was introduced into the deposition chamber in order to initiate the heavy ion bombardment and growth of an ultra-thin (5 nm) i-layer. The structural changes of the p-type nc-Si:H layers were observed by spectroscopic ellipsometry. The obtained results confirm that detrimental structural modifications (e.g. partial amorphization of the sub-surface region and bulk) occur in the p-layer, caused by the ion bombardment. To minimize this effect, a protective buffer layer is investigated able to improve the performance of the solar cells fabricated under increased growth rate conditions. {\textcopyright} 2015 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.tsf.2015.08.016}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942037268\&partnerID=40\&md5=d43075432bd9571cfcda387b3cd1a3df}, author = {Lyubchyk, A.a , Filonovich, S.A.a , Mateus, T.a , Mendes, M.J.a , Vicente, A.a , Leit{\~a}o, J.P.b , Falc{\~a}o, B.P.b , Fortunato, E.a} } @article {Liu2015S75, title = {A water-induced high-k yttrium oxide dielectric for fully-solution-processed oxide thin-film transistors}, journal = {Current Applied Physics}, volume = {15}, year = {2015}, note = {

cited By 0

}, pages = {S75-S81}, abstract = {

In this work, we develop a simple and eco-friendly water-inducement method for high-k yttrium oxide (YOx) dielectric. To prepare YOx thin films at low temperature, yttrium nitrate and deionized water were used as the source materials. No toxic organic materials were required in the YOx coating process. The YOx thin film annealed at 350 {\textdegree}C showed a low leakage current density of 2 {\texttimes} 10-9 A/cm2 at 5 MV/cm and a large areal-capacitance of 448 nF/cm2 at 1 kHz. On the basis of its implementation as the gate dielectric, the fully-water-induced In2O3 TFT based on YOx exhibited a high field-effect mobility of 15.98 cm2/Vs, excellent subthreshold swing of 75 mV/dec, an on/off current ratio of 6 {\texttimes} 106, and a negligible hysteresis of 50 mV. The as-fabricated TFT operated at a low voltage (\~{}1.5 V) and showed high drain current drive capability, enabling oxide TFT with a water-induced high-k dielectric for use in backplane electronics for low-power mobile display applications. {\textcopyright} 2015 Elsevier B.V. All rights reserved.

}, doi = {10.1016/j.cap.2015.04.015}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942369470\&partnerID=40\&md5=7ddc20cb4ad05fcafb6977a61be52dbc}, author = {Liu, A.a , Liu, G.a , Zhu, H.a , Meng, Y.a , Song, H.a , Shin, B.b , Fortunato, E.c , Martins, R.c , Shan, F.a} } @article {Lajn2013, title = {Comparative study of transparent rectifying contacts on semiconducting oxide single crystals and amorphous thin films}, journal = {Journal of Applied Physics}, volume = {113}, number = {4}, year = {2013}, note = {

cited By 7

}, abstract = {

We demonstrate fully transparent, highly rectifying contacts (TRC) on amorphous GaInZnO and compare them to TRC fabricated on single crystalline bulk ZnO and heteroepitaxial ZnO thin films. The contacts{\textquoteright} transparency in the visible spectral range exceeds 70\%. From numerical simulations, we conclude that thermionic emission is the dominating transport mechanism, however, for several samples with low net doping density diffusion theory must be applied. The detailed investigation of the rectification properties of the TRC using temperature-dependent current-voltage and capacitance-voltage measurements reveals that barrier inhomogeneities govern the IV-characteristics of all diodes irrespective of the sample crystallinity. Assuming a Gaussian barrier height distribution, the extracted mean barrier heights typically range between 1.1 and 1.3 V. The width of the barrier distribution correlates with the mean barrier height and ranges from 110 to 130 mV. By compiling literature data, we found that this correlation holds also true for Schottky diodes on elemental and III-V semiconductors. {\textcopyright} 2013 American Institute of Physics.

}, doi = {10.1063/1.4789000}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873660230\&partnerID=40\&md5=a3743ea65f5d7cc06accbf4f71e1f70f}, author = {Lajn, A.a , Von Wenckstern, H.a , Grundmann, M.a , Wagner, G.b , Barquinha, P.c , Fortunato, E.c , Martins, R.c} } @article {Lorenz2010, title = {Low-temperature processed Schottky-gated field-effect transistors based on amorphous gallium-indium-zinc-oxide thin films}, journal = {Applied Physics Letters}, volume = {97}, number = {24}, year = {2010}, note = {

cited By 21

}, abstract = {

We have investigated the electrical properties of metal-semiconductor field-effect transistors (MESFET) based on amorphous oxide semiconductor channels. All functional parts of the devices were sputter-deposited at room temperature. The influence on the electrical properties of a 150 {\textdegree}C annealing step of the gallium-indium-zinc-oxide channel is investigated. The MESFET technology offers a simple route for processing of the transistors with excellent electrical properties such as low subthreshold swing of 112 mV/decade, gate sweep voltages of 2.5 V, and channel mobilities up to 15 cm2 /V s. {\textcopyright} 2010 American Institute of Physics.

}, doi = {10.1063/1.3525932}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650352232\&partnerID=40\&md5=e13e70609dd1668ba97dd55d037eea0e}, author = {Lorenz, M.a , Lajn, A.a , Frenzel, H.a , V. Wenckstern, H.a , Grundmann, M.a , Barquinha, P.b , Martins, R.b , Fortunato, E.b} } @article {Lopes2009, title = {Gate-bias stress in amorphous oxide semiconductors thin-film transistors}, journal = {Applied Physics Letters}, volume = {95}, number = {6}, year = {2009}, note = {

cited By 116

}, abstract = {

A quantitative study of the dynamics of threshold-voltage shifts with time in gallium-indium zinc oxide amorphous thin-film transistors is presented using standard analysis based on the stretched exponential relaxation. For devices using thermal silicon oxide as gate dielectric, the relaxation time is 3{\texttimes} 105 s at room temperature with activation energy of 0.68 eV. These transistors approach the stability of the amorphous silicon transistors. The threshold voltage shift is faster after water vapor exposure suggesting that the origin of this instability is charge trapping at residual-water-related trap sites. {\textcopyright} 2009 American Institute of Physics.

}, doi = {10.1063/1.3187532}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-69049119241\&partnerID=40\&md5=fc7564312a4461ffe4b0cf4d965cd130}, author = {Lopes, M.E.a , Gomes, H.L.a , Medeiros, M.C.R.a , Barquinha, P.b , Pereira, L.b , Fortunato, E.b , Martins, R.b , Ferreira, I.b} } @article {Lopes2002357, title = {Study of the sensing mechanism of SnO2 thin-film gas sensors using hall effect measurements}, journal = {Key Engineering Materials}, volume = {230-232}, year = {2002}, note = {

cited By 1

}, pages = {357-360}, abstract = {

Hall effect measurements are one of the most powerful techniques for obtaining information about the conduction mechanism in polycrystalline semiconductor materials, which is the basis for understanding semiconductor gas sensors. In order to investigate the correlation between the microscopic characteristics and the macroscopic performances exhibited by undoped tin oxide gas sensors deposited by spray pyrolysis, Hall effect measurements were performed at different temperatures, from room temperature up to 500 K, and in the presence of two different atmospheres, air and methane. From these measurements, it was possible to infer the potential barrier and its dependence with the used atmosphere. The obtained results were analysed in terms of the oxygen mechanism at grain boundaries on the basis of the grain boundary-trapping model. In the presence of methane gas, the electrical resistivity decreases due to the lowering of the inter-grain boundary barrier height.

}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036432225\&partnerID=40\&md5=4fac5ab5a508bad2f6a93846618e74ba}, author = {Lopes, A., Nunes, P., Vilarinho, P., Monteiro, R., Fortunato, E., Martins, R.} } @article {Lopes20011349, title = {Correlation between the microscopic and macroscopic characteristics of SnO2 thin film gas sensors}, journal = {International Journal of Inorganic Materials}, volume = {3}, number = {8}, year = {2001}, note = {

cited By 5

}, pages = {1349-1351}, abstract = {

Hall effect measurements have been used to evaluate the conduction mechanism, exhibited by tin oxide thin film gas sensors deposited by spray pyrolysis. Two experiments have been carried out: (i) Hall measurements in air and (ii) in the presence of methane (first results reported), both as a function of temperature. From the measurements performed it was possible to infer the potential barrier and its dependence with the atmosphere used. The results obtained for the carrier concentration and mobility have been analysed in the light of the oxygen diffusion mechanism at grain boundaries by using the grain boundary-trapping model. In the presence of the methane gas the electrical resistivity decreases due to the lowering of the inter-grain boundary barrier height. {\textcopyright} 2001 Published by Elsevier Science Ltd.

}, doi = {10.1016/S1466-6049(01)00160-X}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035208785\&partnerID=40\&md5=6bc97140eef5cbab24ad760cd7949098}, author = {Lopes, A.a , Fortunato, E.a , Nunes, P.a , Vilarinho, P.b , Martins, R.a} } @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.} } @article {Lavado1989791, title = {Electron paramagnetic resonance of defects in doped microcrystalline silicon}, journal = {Vacuum}, volume = {39}, number = {7-8}, year = {1989}, note = {

cited By 0

}, pages = {791-794}, abstract = {

Experimental results on structure defects in microcrystalline (μc) n- and p-doped μc-S1-x:Cx:H films deposited on alkali-free glass substrates by spatial plasma separation1 and obtained by electron paramagnetic resonance (EPR) are presented. The technique used for subtracting the substrate effect on recorded spectra is also discussed as well as its quantification. The microscopic structure of intrinsic defects and impurity states and their role in transport mechanisms are studied and correlated with the composition of their films. These results are also related to transport properties of deposited films in order to observe the role of dopant centres, located at conduction band tails, in controlling the electrical properties. {\textcopyright} 1989.

}, doi = {10.1016/0042-207X(89)90039-0}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024876089\&partnerID=40\&md5=e21bef0d3b3614a3c1fd831127592d76}, author = {Lavado, M., Martins, R., Ferreira, I., Lavareda, G., Fortunato, E., Vieira, M., Guimar{\~a}es, L.} }