Papers by Author: Z. Hassan

Abstract: This study reports on the fabrication of a Schottky solar cell with a cross-sectional schematic: ITO/PbS/Al with a commercial transparent conductive ITO and a p-type PbS absorber layer deposited by using a thermal evaporator. The structural and optical properties of constituent films are presented. X-ray diffraction showed that the thin films are polycrystalline. By using scanning electron microscopy, this study showed that the films possessed a uniform surface morphology over the substrate, and the films exhibit a nanocoral structure. Open circuit voltage,short-circuit current density and characteristics were studied under 30 mW/cm² solar radiation.

Abstract: t will be demonstrated that light extraction of GaNcan be more efficient with the use of flat and dome epoxy. Theoretically the angle, wavelength, and thickness depend on the photoluminescence emission of the luminescent film of transparent substrate. This was studiedusing theFresnel type transmittance calculations for s- (TE) and p- (TM) polarized emission. Experimentally we have demonstrated a GaN/sapphire microcavity exhibited in the 1.3-1.6 fold enhancement in light extraction efficiency by using flat and dome epoxy as external medium compared with air external medium. In addition, simulation results shows that using (HfO₂(), Epoxy (),MgF₂ (), Air ()) improve the light extraction by increasingthe critical angle and diffracting the internal light with a large solid angle into the light escape cone.

Abstract: Al thin films were prepared over different substrates at various process conditions using DC sputtering. The surface topography of all prepared films was examined using AFM technique. Very smooth, uniform and dense surface were observed for Al films coated over Glass substrates. The observed particle size was nano scale (20 -70 nm) for Glass substrates. Sputtering power showed immense effect on surface roughness with respective to Ar gas flow rate. Noticeable change on surface with large particles was observed in Copper substrates at various sputtering power and gas flow rate.

Abstract: In this paper, we have grown high-quality wurtzite GaN nanowires (NWs) on polished <111> silicon (Si) either with or without gold (Au) as catalyst, by thermal evaporation using commercial GaN powder in an atmosphere of argon (Ar) gas. Optical and structural characterizations were performed using photoluminescence (PL), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and high resolution X-ray diffraction (HR-XRD). Structural characterizations indicate that the nanowires are of single-crystal hexagonal GaN. By using catalyst the growth location and diameters of the NWs can be controlled. The NWs on the Si are of higher density, and the compositional quality of the grown NWs on the Si substrate is of pure GaN as compare to the Au-coated substrate.

Abstract: Nanocrystalline PbS thin films were prepared using chemical bath deposition method on glass substrates, together with lead acetate as a source of lead ions (Pb²⁺) and thiourea as a source of sulfide ions (S^2-) with different molar concentrations. The structural properties of thin films were studied using X-ray diffraction.The patterns showed a polycrystalline structure, and the preferred orientation changed along (111) and (200) planes .The grain size of the thin films varied from 27 to 41 nm. The crystallites were under strain, which varied between 0.054 and 0.3. Scanning electron microscope images showed that all the films have uniform surface morphology over the entire glass substrate and that the films were of good quality.