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Article Citation - WoS: 9Citation - Scopus: 9Optical Dynamics in the Ag/Α-ga2< Layer System(Elsevier Sci Ltd, 2018) Alharbi, S. R.; Qasrawi, A. F.In this work, thin films of Ga2S3 are deposited onto 150 nm thick transparent Ag substrate by the physical vapor deposition technique under vacuum pressure of 10(-5) mbar. The films are studied by the X-ray diffraction and optical spectrophotometry techniques. It is found that the Ag substrate induced the formation of the monoclinic alpha-Ga2S3 polycrystals. The transparent Ag substrate also changed the preferred optical transition in Ga2S3 from direct to indirect It also increased the light absorption by 79 and 23 times at incident light energies of 2.01 and 2.48 eV, respectively. In addition, a red shift in all types of optical transitions is observed. Some the extended energy band tails of Ag appears to form interbands in the band gap of Ga2S3. These interbands strongly attenuated the dielectric and optical conduction parameters. Particularly, an enhancement in the dielectric constant values and response to incident electromagnetic field is observed. The Drude-Lorentz modeling of this interface has shown that the free carrier density, drift mobility, plasmon frequency and reduced electron-plasmon frequency in Ga2S3 increases when the Ag substrate replaced the glass or other metals like Yb, Al and Au. The nonlinear optical dynamics of the Ag/Ga2S3 are promising as they indicate the applicability of this interface for optoelectronic applications.Article Citation - WoS: 11Citation - Scopus: 10Optical Conduction in Amorphous Gase Thin Films(Elsevier Gmbh, 2016) Qasrawi, A. F.; Khanfar, Hazem. K.; Kmail, Renal R. N.In this work, the optical conduction mechanism in GaSe thin films was explored by means of dielectric spectral analysis in the 270-1000 THz range of frequency. The GaSe films which are found to be amorphous in nature are observed to follow the Lorentz approach for optical conduction. The modeling of the optical conductivity which takes into account the damped electronic motion resulting from the collision of photogenerated carriers with impurities, phonons and other damping sources allowed determining the optical conduction parameters. Particularly, an average carrier scattering time, a free carrier density, a reduced resonant frequency, a field effect mobility and an electron bounded plasma frequency of 0.142 (fs), 1.7 x 10(19) (cm(-3)), 875.8 (THz), 1.25 (cm(2)/Vs) and 82.8 (THz), respectively, were determined. These parameters are promising as they indicate the applicability of GaSe in the technology of mid-infrared plasmonic nanoantennas. In addition, the dielectric optical signal which displayed a resonance peak at 500 THz seems to be attractive for use in passive modes operating optoelectronic devices like field effect transistors as they exhibit an increasing signal quality factor with decreasing incident light frequency (C) 2016 Elsevier GmbH. All rights reserved.
