Martins, R., Ferreira Cabrita Fortunato I. A. E. "
Improvement of a-Si:H device stability and performances by proper design of the interfaces."
Journal of Non-Crystalline Solids. 266-269 B (2000): 1094-1098.
AbstractThis 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. © 2000 Elsevier Science B.V. All rights reserved.
Martins, R., Ferreira Carvalho Guimarães I. N. L. "
Engineering of plasma deposition systems used for producing large area a-Si:H devices."
Journal of Non-Crystalline Solids. 137-138 (1991): 757-760.
AbstractOne of the main problems in producing large area amorphous silicon devices concerns films uniformity. In this paper we present data concerning the role of reactor geometry and design and on the film performances as well as the problems related to mechanical mismatches in scaling up the reactor size. © 1991 Elsevier Science Publishers B.V. All rights reserved.
Martins, R., Fortunato E. "
Static and dynamic resolution of 1D thin film position sensitive detector."
Journal of Non-Crystalline Solids. 198-200 (1996): 1202-1206.
AbstractThe aim of this work is to present a model to interpret the static and the dynamic detection and resolution limits of 1D thin film position sensitive detectors based on p-i-n a-Si:H devices. The model can determine the device characteristics that influence the spatial limits and the response time of the device.
i Martins, R.a, Águas Ferreira Fortunato Raniero Roca Cabarrocas H. a I. a. "
Composition, structure and optical characteristics of polymorphous silicon films deposited by PECVD at 27.12 MHz."
Materials Science Forum. 455-456 (2004): 100-103.
AbstractThis paper presents data concerning the composition structure and optical characteristics of polymorphous silicon films produced by plasma enhanced chemical vapour deposition at 27.12 MHz and determined respectively by infrared spectrometry, micro Raman, exodiffusion and spectroscopic ellipsometry measurements. When compared to the pm-Si:H films produced at 13.56 MHz, the films produced at 27.12 MHz present hydrogen contents in the range of 21 at%, the sharp peak ascribed to the exodifusion measurements is shifted towards high temperatures and the imaginary part of the dielectric function 〈ε2〉 is larger and shifted to high energies. Apart from that the peaks of the infrared spectra ascribed to the stretching modes shift towards high wave numbers and the half width of the micro Raman peaks shrinks, meaning that the films produced at 27.12 MHz are more compact and dense.
Martins, R., Águas Silva Ferreira Cabrita Fortunato H. V. I. "
Nanostructured silicon films produced by PECVD."
Materials Research Society Symposium - Proceedings. Vol. 664. 2001. A961-A966.
AbstractThis paper presents the process conditions that lead to the production of nanostructured silicon films grown by plasma enhanced chemical vapour deposition close to the so-called gamma regime (powder formation), highly dense and with low density of bulk states. Thus, the powder management is one important issue to be addressed in this paper. As a general rule we observed that high quality films (low density of states and high μτ products) are obtained when films are grown under low ion bombardment at high hydrogen dilution and deposition pressure conditions, to allow the proper surface passivation and surface activation.
Martins, Rodrigo, Lavareda Guilherme Fortunato Elvira Soares Fernando Fernandes Luis Ferreira Luis. "
Linear thin-film position-sensitive detector (LTFPSD) for 3D measurements."
Proceedings of SPIE - The International Society for Optical Engineering. Vol. 2415. 1995. 148-158.
AbstractA linear array thin film position sensitive detector (LTFPSD) based on hydrogenated amorphous silicon (a-Si:H) is proposed for the first time, taking advantage of the optical properties presented by a-Si:H devices we have developed a LTFPSD with 128 integrated elements able to be used in 3-D inspections/measurements. Each element consists on a one-dimensional LTFPSD, based on a p.i.n. diode produced in a conventional PECVD system, where the doped layers are coated with thin resistive layers to establish the required device equipotentials. By proper incorporation of the LTFPSD into an optical inspection camera it is possible to acquire information about an object/surface, through the optical cross-section method. The main advantages of this system, when compared with the conventional CCDs, are the low complexity of hardware and software used and that the information can be continuously processed (analogue detection).
Malik, A., Nunes Martins R. R. "
Cubic to hexagonal phase transition in spray deposited tin-doped indium oxide films."
Materials Research Society Symposium - Proceedings. Vol. 481. 1998. 599-605.
AbstractThis work's aim is to report for the first time the cubic to hexagonal phase transition in tin-doped In2O3 films with a Sn/In atomic ratio of 0.03, fabricated at low temperature and normal pressure from alcoholic solution of InCl3 and SnCl4. The performed X-ray diffraction measurements show a difference between crystallographic symmetry of thin (100 nm) and thick (400 nm) films prepared in the same conditions: the structure of thick films can be related to high pressure In2O3 hexagonal system with a preferred orientation of c-axis parallel to the substrate surface, while thin films present a cubic symmetry with columnar (400) grain orientation. Phase transition nature is connected with non-axial tensile deformation of indium oxide grid due to insertion of chlorine ions in the position of two diagonally opposite oxygen vacancies in In2O3 network.
Malik, A.a, Sêco Fortunato Martins A. c E. b. "
Microcrystalline thin metal oxide films for optoelectronic applications."
Journal of Non-Crystalline Solids. 227-230 (1998): 1092-1095.
AbstractWe report the properties and optoelectronic applications of transparent and conductive indium and tin oxide films prepared by the spray pyrolysis method and doped with Sn or F, respectively. The film properties have been measured using X-ray diffraction, optical and electrical absorption. As examples of applications we produced a set of selective optical detectors for different spectral regions, covering the wavelength range from 0.25 to 1.1 μm, based on metal oxide-semiconductor heterostructures and using different substrates such as: GaP, GaSe, AlxGa1-xAs, GaAs and Si. The fabricated devices exhibit several features such as: production simplicity, high quantum efficiency, uniform sensitivity over the entire active area and a high response speed. Finally, we present a high quantum efficiency and solar blind monocrystalline zinc sulphide optical sensor fabricated by spray deposition as an alternative to the ultraviolet-enhanced SiC and GaN photodetectors and the performances of a solar cell. © 1998 Elsevier Science B.V. All rights reserved.