Ferreira, I.M.M., Cabrita Fortunato Martins A. M. F. E. "
N-type silicon films produced by hot wire technique."
Materials Research Society Symposium - Proceedings. Vol. 609. 2000. A651-A656.
AbstractThe role of the deposition pressure (p) and the type of filaments (tungsten, W or tantalum, Ta) used to produce large area (10cm×10cm) n-type Si:H films by hot wire chemical vapour (HW-CVD) deposition technique was investigated. The data show that the electro-optical properties of the films produced are dependent on the gas pressure used. In the pressure range of 1×10-3 Torr to 1.0 Torr, the room dark conductivity (σd) varies from 1×10-8 to 2 S/cm for films produced at the same hydrogen dilution and filament temperature (Tfil). On the other hand, the hydrogen concentration (CH) decreases from 10% to 2%, while the growth rate (R) shows an exponential increase, from 1 to 9 Å/s. The SIMS analysis, within the detection limits, does not reveal the existence of any significant W or Ta contamination in the films produced.
Ferreira, I.M.M., Martins Cabrita Fortunato Vilarinho R. F. P. A. "
Nanocrystalline undoped silicon films produce by hot wire plasma assisted technique."
Materials Research Society Symposium - Proceedings. Vol. 609. 2000. A2241-A2246.
AbstractIn this work, we show results concerning electro-optical properties, composition and morphology of nanocrystalline hydrogenated undoped silicon (nc-Si:H) films produced by hot wire plasma assisted chemical vapour deposition process (HWPA-CVD) and exhibiting a compact granular structure, as revealed by SEM micrographs. This was also inferred by infrared spectra, which does not present the SiO vibration band located at 1050-1200 cm-1, even when samples have long atmospheric exposition. The photoconductivity measured at room temperature also does not change when samples have a long time exposition to the air or to the light irradiation. The influence of hydrogen dilution on the properties of the films was also investigated.
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.
Carvalho, J., Ferreira Fernandes Fidalgo Martins I. B. J. "
Nd-YAG laser induced crystallization on a-Si:H thin films."
Materials Research Society Symposium - Proceedings. Vol. 358. 1995. 915-920.
AbstractIn this paper we present results concerning the influence of laser energy and shot density on the electrical resistance, X-ray diffraction pattern, and structure obtained by SEM, on recrystallized a-Si:H thin films produced by using a Nd-YAG laser, working in a wavelength of 532 nm. The base material (undoped and doped a-Si:H) was obtained by Plasma Enhanced Chemical Vapour Deposition (PECVD). The structure and electrical characteristics of the recrystallized thin films are dependent on the laser beam energy density, beam spot size and the number of shots applied to the base a-Si:H thin film used. Overall, the data show recrystallized material with grain sizes larger than 1μm, where the electrical resistance of both, undoped and doped materials, can be varied up to 5 orders of magnitude, by the proper choice of the recrystallization conditions.
Fortunato, E., Barquinha Gonçalves Pereira Martins P. G. L. "
New amorphous oxide semiconductor for thin film transistors (TFTs)."
Materials Science Forum. 587-588 (2008): 348-352.
AbstractThin film transistors (TFTs) have been produced by rf magnetron sputtering at room temperature, using non conventional oxide materials like amorphous indium-zinc-oxide (IZO) semiconductor, for the channel as well as for the drain and source regions. The obtained TFTs operate in the enhancement mode with threshold voltages of 2.4 V, saturation mobility of 22.7 cm2/Vs, gate voltage swing of 0.44 V/dec and an ON/OFF current ratio of 7×10 7. The high performances presented by these TFTs associated to a high electron mobility, at least two orders of magnitude higher than that of conventional amorphous silicon TFTs and a low threshold voltage, opens new doors for applications in flexible, wearable, disposable portable electronics as well as battery-powered applications.
Fortunato, E., Barquinha Martins P. R. "
New developments on oxide electronics."
Proceedings of the International Display Workshops. Vol. 3. 2011. 1681-1684.
AbstractIn this article we review the recent progress in n- and p-type oxide based thin film transistors (TFT), with special emphasis to solution-processed and p-type, and we will summarize the major milestones already achieved with this emerging and very promising technology.
Fortunato, E., Soares Lavareda Martins F. G. R. "
New linear array thin film position sensitive detector (LTFPSD) for 3D measurements."
Materials Research Society Symposium - Proceedings. Vol. 377. 1995. 797-802.
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 3D inspections/measurements. Each element consists on an one-dimensional TFPSD, 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 will be 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).