Ferreira, I., Vilarinho Fernandes Fortunato Martins P. F. E. "
Influence of hydrogen gas dilution on the properties of silicon-doped thin films prepared by the hot-wire plasma-assisted technique."
Key Engineering Materials. 230-232 (2002): 591-594.
AbstractP- 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 × 10-2(Ωcm)-1 and 1.6eV, respectively. The films exhibit the required optoelectronic characteristics and compactness for device applications such as solar cells.
Ferreira, I., Águas Pereira Fortunato Martins H. L. E. "
Properties of a-Si:H intrinsic films produced by HWPA-CVD technique."
Thin Solid Films. 451-452 (2004): 366-369.
AbstractIn this paper, we investigate the optoelectronic properties and the photodegradation of amorphous silicon films produced by the hot wire plasma assisted technique (HWPA-CVD). We observed that hydrogen dilution in the gas phase plays an important role in the time dependence of the photoconductivity, which is correlated with an enhancement of defect density. We also compare the degradation of these films with those produced by plasma enhanced and by hot wire chemical vapour deposition techniques (PECVD and HW-CVD) and we found lower time dependence for the photodegradation of the films produced by HWPA-CVD technique © 2003 Elsevier B.V. All rights reserved.
Fortunate, E., Assunção Marques Ferreira Águas Pereira Martins V. A. I. "
Characterization of transparent and conductive ZnO:Ga thin films produced by rf sputtering at room temperature."
Materials Research Society Symposium - Proceedings. Vol. 763. 2003. 225-230.
AbstractGallium-doped zinc oxide films were prepared by rf magnetron sputtering at room temperature as a function of the substrate-target distance. The best results were obtained for a distance of 10 cm, where a resistivity as low as 2.7×10-4 Ωcm, a Hall mobility of 18 cm2/Vs and a carrier concentration of 1.3×1021 cm-3 were achieved. The films are polycrystalline presenting a strong crystallographic c-axis orientation (002) perpendicular to the substrate. The films present an overall transmittance in the visible part of the spectra of about 85 %, in average. The low resistivity, accomplished with a high growth rate deposited at RT, enables the deposition of these films onto polymeric substrates for flexible applications.
Fortunate, E.a, Ferreira Giuliani Wurmsdobler Martins I. a F. a. "
New ultra-light flexible large area thin film position sensitive detector based on amorphous silicon."
Journal of Non-Crystalline Solids. 266-269 B (2000): 1213-1217.
AbstractIn this paper we report on large area one dimensional (1D) amorphous silicon position sensors deposited on flexible polymer foil substrate. The pin sensor structure was deposited by rf plasma enhanced chemical vapour deposition (PECVD). For the electrical and optical characterisation the sensors have been mounted on a convex holder with a 14-mm radius-of-curvature, since the main goal of this work is to develop a flexible position sensor to be incorporated in a micromotor in order to measure its angular velocity continuously. The obtained sensors present adequate performances concerning the position non-linearity (±1% in 20 mm length), comparable to those fabricated on glass substrates. © 2000 Elsevier Science B.V. All rights reserved.
Fortunate, E., Gonçalves De Carvalho Pimentel Lavareda Marques Martins A. C. N. "
Enhancement of the electrical properties of ITO deposited on polymeric substrates by using a ZnO buffer layer."
Materials Research Society Symposium Proceedings. Vol. 814. 2004. 231-236.
AbstractIn this paper we present the effect of the insertion of a non-doped nanocrystalline zinc oxide/buffer layer on the electrical, optical and structural properties of indium tin oxide produced at room temperature by radio frequency plasma enhanced reactive thermal evaporation on polymeric substrates. The electrical resistivity of the ITO films is reduced by more than two orders of magnitude (4.5×10-1 to 2.9×10-3 Ωcm). From the Hall effect measurements it is observed that the large decrease associated to the electrical resistivity, is due to the increase associated to the Hall mobility. Concerning the optical properties no effect was observed, being the transmittance in the visible and near the infra red region always higher than 80%.
Fortunato, E., Martins R. "
Role of the collecting resistive layer on the static characteristics of 2D a-Si:H thin film position sensitive detector."
Materials Research Society Symposium - Proceedings. Vol. 507. 1999. 303-308.
AbstractThe aim of this work is to present an analytical model able to interpret the role of the thin collecting resistive layer on the static performances exhibited by 2D amorphous silicon hydrogenated pin thin film position sensitive detectors. In addition, experimental results concerning the device linearity and spatial resolution are presented and checked against the predicted values of the analytical model proposed.
Fortunato, E., Pimentel Gonçalves Marques Martins A. A. A. "
High mobility nanocrystalline indium zinc oxide deposited at room temperature."
Materials Research Society Symposium Proceedings. Vol. 811. 2004. 437-442.
AbstractIn this paper we present results of indium doped zinc oxide deposited at room temperature by rf magnetron sputtering, with electron mobility as high as 60 cm2/Vs. The films present a resistivity as low as 5×10 -4 Ωcm with an optical transmittance of 85%. The structure of these films look-like polymorphous (mixed of different amorphous and nanocrystalline phases from different origins) as detected from XRD patterns (no clear peak exists) with a high smooth surface, as detected from SEM micrographs, highly important to ensure long life time when used in display devices.
Fortunato, E., Malik Martins A. R. "
Thin oxide interface layers in a-Si:H MIS structures."
Journal of Non-Crystalline Solids. 227-230 (1998): 1230-1234.
AbstractPd-metal/insulator/semiconductor based on hydrogenated amorphous silicon were produced by plasma enhanced chemical vapour deposition with two different oxidised surfaces: thermal in ambient air and chemical with hydrogen peroxide. The diode characteristics have been investigated using dark and light current as f(v) measurements in the temperature range from 300 K to 380 K, from which it was possible to infer the electron barrier height. The data obtained show that the incorporation of a thin insulator layer between the semiconductor and the metal improves the performances of the devices by preventing the formation of suicides at the interface. Apart from that we also show that the MIS structures with the thermal oxide presents 'better' performances than the ones with the chemical oxide due to the type of interface states and of the oxide charges associated with the interface between the insulator and the semiconductor. © 1998 Elsevier Science B.V. All rights reserved.