Papers by Author: A. Keffous

Abstract: In this paper we present the study of a Schottky diode gas sensing by using porous SiC films with palladium as a catalytic metal. The Schottky diodes were used for the first time for hydrocarbon (C2H6) gas sensing. The properties of the porous SiC films formed by electrochemical method were investigated by scanning electron microscopy (SEM). The electrical measurements were made at room temperature (295 K) in different ambient. The effect of the porous surface structure was investigated by evaluating electrical parameters such as the ideality factor (n), barrier height (Bp) and series resistance (Rs). The porous layer significantly affects the electrical properties of the Schottky diodes. Analysis of current-voltage (I-V) characteristics showed that the forward current might be described by a classical thermal emission theory. The ideality factor determined by the I–V characteristics was found to be dependent on the SiC thickness. For a thinner SiC layer (0.16 µm), the electrical parameters n was found around 1.135, 0.7041 eV for a barrier height and 45  for a series resistance, but for a thicker one (1.6 µm) n, Bp and Rs were 1.368, 0.7756 eV and 130 , respectively. The low value of the series resistance obtained using Cheung’s method clearly indicated the high performance of the Schottky diode for thinner SiC layer. This effect showed the uniformity of the SiC layer. Finally, sensitivity around 66 % and selectivity of the sensors were reached by using the PSC layer at low voltages below 0.5 Volt.

Abstract: Boron-doped hydrogenated amorphous silicon (a-Si:H(B)) thin films have been prepared by DC magnetron sputtering technique under argon and hydrogen mixture. The films were deposited at various hydrogen pressures between 0 and 9 10-5 mbar. The boron concentration estimated from Secondary Ion Mass Spectrometry (SIMS) analysis was found to be around 1.5 1021 cm-3 for all samples. Their physico-chemical, optical and electrical properties are investigated. The physico-chemical properties were studied by infrared absorption measurements. The bonded hydrogen content in the films is then determined using the absorption band of stretching mode. The optical transmission measurements show an increase of the static refractive index and a decrease of optical gap value when hydrogen pressure increases. The dark-conductivity and the photo-conductivity measurements according to the temperature are also reported. We have observed the decreasing of dark-conductivity when hydrogen pressure increases. A slight sensitivity of light was observed for the film deposited at the highest hydrogen pressure. The dark-conductivity was affected by annealing temperature for the whole of the films through its increase in the annealing temperature region 200-350°C.