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This study was on the optoelectronic properties of multilayered two-dimensional MoS2 and WS2 materials on a silicon substrate using sputtering physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques. For the first time, we report ultraviolet (UV) photoresponses under air, CO2, and O2 environments at different flow rates. The electrical Hall effect measurement showed the existence of MoS2 (n-type)/Si (p-type) and WS2 (P-type)/Si (p-type) heterojunctions with a higher sheet carrier concentration of 5.50 × 105 cm−2 for WS2 thin film. The IV electrical results revealed that WS2 is more reactive than MoS2 film under different gas stimuli. WS2 film showed high stability under different bias voltages, even at zero bias voltage, due to the noticeably good carrier mobility of 29.8 × 102 cm2/V. WS2 film indicated a fast rise/decay time of 0.23/0.21 s under air while a faster response of 0.190/0.10 s under a CO2 environment was observed. Additionally, the external quantum efficiency of WS2 revealed a remarkable enhancement in the CO2 environment of 1.62 × 108 compared to MoS2 film with 6.74 × 106. According to our findings, the presence of CO2 on the surface of WS2 improves such optoelectronic properties as photocurrent gain, photoresponsivity, external quantum efficiency, and detectivity. These results indicate potential applications of WS2 as a photodetector under gas stimuli for future optoelectronic applications.

The results of single television observations of Perseid meteor shower in 2016 are presented. The Perseid shower occurs from 17 July to 24 August, peaking on or around August 12 every year. In 2016, the peak of the Perseids was Night of Aug 11 to the morning of Aug 12. The meteor video observations in Egypt are carried out at The National Researcher Institute of Astronomy and Geophysics (NRIAG). The system consists of TV - cameras Watec -902H Ultimate with the lens DV10x8SA-1 (8-80 mm (10x)) capable of recording the rapid motion of meteors entering the Earth atmosphere.

Nano crystalline Tin oxide thin film of multiple layers was successfully prepared by the sol-gel method with, spin coater has been used to deposit the films. The starting material is SnCl2. The SnO2 material was characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM). The optical properties (A, T, R) of the SnO2 thin film of various annealing temperatures (400,500,600 Co) have been studied. Characterization results indicated that the products are composed of crystalline SnO2 nanoparticles which exhibit the cassiterite-type tetragonal crystal structure. SEM revealed that with increase annealing temperature, the uniformity of the film increased. XRD measurements showed that the grain size increased from 1.06, 1.48, 1.71 nm. The variations of the refractive index (n), extinction coefficient (K) and Optical Conductivity with the wavelength have been studied. Nevertheless, the variation of the optical band gap with film thicknesses shows a significantly decrease in the values of the band gap with increase the film thicknesses. Shaban et al. (2014), Synthesis and characterization of Tin oxide thin film, effect of annealing on multilayer film, J. Modern Trends in Phys. R., Vol. 14 90-99 https://doi.org/10.19138/mtpr/(14)90-99 98 Fig.10 (a, b). The variation of extinction coefficient(K) and refractive index(n), respectively, of SnO2 thin film of 12 layers which annealed at 400,500,600 C o CONCLUSIONWe studied the effect of annealing temperature on a multilayer spin coated tin oxide thin films by sol-gel technique. It was found that the surface morphology changes with the different annealing temperatures. The transmittance and the optical band gap decrease with increase the film thickness while the refractive index increases.

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