M.S. Aida

Surface state dependence of PbS and PbSe infrared noise and detectivity

It is established that the surface state is one of the most important mechanisms limiting the performance of photoconductors. In a previous work, we have presented the theoretical platform of surface state model exhibiting the analysis of the space charge region at the free surface of semiconductors. To know that recombination effects directly influence the quantum efficiency of detector, the dependence of some detector parameters on surface defect densities and the comparison of this model with experimental data of responsivity are evaluated. The present papers use this model to explore the dependence of surface parameters on signal, noise and detectivity. The results of the model are compared with the experimental results for p-PbS case.

Ammonia free growth of CdS thin films by Chemical Bath Technique

CdS thin films were deposited by a chemical bath deposition technique (CBD). The bath solution is composed of CdCl2 (0.1 M) salt as a source for Cd and thiourea (0.1M) as a source of sulphur (S). To avoid the toxicity and volatility of the commonly used ammonia, ethanolamine (ETA ) is used as complexing agent. Films were deposited with different times from 30 to 120 minutes in order to study the films growth mechanism. The solution temperature was fixed at 60°C. The structural and morphological films characterizations were carried by XRD analysis and AFM observations. From the XRD analysis we inferred that obtained CdS films have a pure hexagonal structure with the preferential orientation along the plane (101). The pure hexagonal structure is highly recommended for the realization of CdTe/ CdS or CuInSe/CdS solar cells. The presence of the hexagonal structure and the low growth rate in order of 1nm/min suggest that the growth mechanism is achieved through the ion by ion process. The optical characterizat...

Microstructure and opto-electrical properties of SnO2:In2O3 alloys thin films prepared by ultrasonic spray

In this work, we study the effect of indium weight ratio in solution: R = [In/Sn] on the properties of SnO2:In2O3 thin films prepared by ultrasonic spray method at fixed temperature of 300°C. The used precursors are tin chloride dehydrate and indium trichloride dissolved in methanol. To prepare hybrid SnO2:In2O3 thin films with different concentrations, the ratio R is varied in the range of 10–95 wt%. The resulting films were characterised by X-ray diffraction, scanning electron microscopy analysis, UV-visible spectrophotometer and conductivity measurement. The XRD results indicate segregation between SnO2 and In2O3 phases in all films. The optical transmittance is in the range of [75–85]%. The conductivity values of pure oxides are very low [~10–3 (Ω.cm)–1] and it is increased with R ratio until a maximum value of 1.2 × 102 (Ω.cm)–1 obtained at R = 95 wt%. Consequently, the higher figure of merit (Fm = σ.T.d) is obtained at this later ratio.