Physical and optical studies of the novel non-crystalline CuxGe20-xSe40Te40 bulk glasses and thin films

Abstract

In this research work, the authors devoted their efforts to study the physical and optical properties of the novel CuxGe20-xSe40Te40, CGST (x = 0,5,10,15,20 at.%) matrix. Physical properties of bulk samples and optical properties of thin films of this matrix have been studied. The bulk glassy samples were prepared using the known melt quenching method, while thin-film samples were deposited by vacuum deposition technique under pressure 10−4 Pa. X-ray diffraction examination showed that thin-film samples were deposited in the amorphous state, where no discrete sharp diffraction peaks were formed. Energy-dispersive X-ray spectroscopy exhibited also that there is a good agreement between the experimental results and the selected elemental composition ratios for all samples. The optical properties were studied using the spectrophotometric measurements of transmittance and reflectance spectra within the spectral range 300 nm–2500 nm. The absorption coefficient, the absorption index, optical energy gap, Urbach energy and others have been investigated and discussed on the view of the chemical band approach model. The optical energy gap decreases from 1.208 eV to 1.045 eV, while Urbach energy increases from 0.186 eV to 0.219 eV as Cu ratio increased from zero to 20%. These CGST samples showed very low absorbance nature in the NIR and IR regions. Therefore, they can be used in the applications of optoelectronics devices, infrared imaging, and optical filters and detectors.