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In present study, dependence of structural and optical properties of nanocrystalline Zn40Te60 (ZnTe) thin films on vacuum thermal annealing has been investigated. ZnTe alloy was prepared by melt quenching technique and thermally evaporated on cleansed glass substrates to deposit thin films. These films were annealed in vacuum (∼1×10-3 mbar) for an hour at three different temperatures 100, 200 and 300 °C. X-ray diffraction results revealed the presence of cubic ZnTe phase in all the films along with some hexagonal Te phase. The crystallite size of ZnTe thin films improved on annealing with larger size at elevated temperatures (from 32 to 80 nm). Micro strain and dislocation density reduced owing to improvement in crystallinity after annealing. The IR transmittance increased with increase in annealing temperature. Field emission scanning electron microscopy images suggested the formation of smooth and uniform thin films with thickness of ∼ 480 nm. Optical properties revealed the decrease in transmittance and absorption edge shift due to crystallinity improvement on annealing. The optical band gap decreased from 1.37 to 0.91 eV on annealing. Experimental results show that thermal annealing has significant impact on structural and optical properties of ZnTe thin films. [ABSTRACT FROM AUTHOR]

In this work, the effect of visible light on the structural, morphological and optical properties of $$(\hbox {Ge}_2\hbox {Sb}_2\hbox {Te}_5)_{100-x}\hbox {Ag}_x$$ ( $$\hbox {x} = 0, 1$$ and 3) thin films prepared by thermal evaporation was studied. Deposited thin films were exposed to visible light of intensity $$10^{4}$$ and $$10^{5}$$ Lux for the duration of 2, 4, 8 and 20 h. Prepared samples were characterized with X-ray diffraction (XRD), Scanning electron microscope (SEM) and UV-Vis-NIR spectrophotometer. The amorphous nature of as-deposited and visible light exposed thin films was confirmed by XRD. The SEM images did not show significant change in the morphology of thin films after visible light exposure. The optical transmission of as-deposited and exposed thin films was measured by UV-Vis-NIR spectrophotometer in the wavelength range of 500-3300 nm. Optical transmission was used to calculate the absorption coefficient and optical band gap. Photo-darkening (decrease in optical band gap) with light exposure was observed in $$(\hbox {Ge}_2\hbox {Sb}_2\hbox {Te}_5)_{100-x}\hbox {Ag}_x$$ ( $$\hbox {x} = 0, 1$$ and 3) thin films. Photo-darkening may be attributed to the enhanced lone pair-lone pair interactions which broaden the valence band and hence decrease the optical band gap. Thus, change in optical parameters is because of change in local structure of deposited thin films. [ABSTRACT FROM AUTHOR]

Thin films of (GeSbTe)Ag (x = 0, 1, 3, 5 and 10) were deposited using thermal evaporation technique. X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy was used to confirm the amorphous nature, uniformity and chemical compositions of deposited films respectively. Transmission spectra divulged the highly transparent nature of films in near infra red region. The average transmission in near infra red region and optical band gap (estimated by Tauc's plot) was increased with Ag doping upto x = 3 while it decreased for higher values of x. The increase in transmission and optical band gap was attributed to the reduction in density of localized states and vacancies. However, the decrease in the transmission and optical band gap is due to the increase in distortion of the host GeSbTe lattice because Ag is doped at the expense of Ge, Sb and Te. The increased optical band gap could be utilized to reduce threshold current which enhances switching speed in phase change materials. [ABSTRACT FROM AUTHOR]

Abstract: An environment friendly, inexpensive solvothermal route is used to synthesize polycrystalline Zn x Sn1−x O2 (0.0≤ x ≤0.07) nanorods with nanoflower morphology without using any organic solvents, surfactant or any catalytic agent under low hydrothermal pressure. Scanning electron microscopy (SEM) equipped with energy-dispersive x-ray spectra depicts the formation of near stoichiometric Zn x Sn1−x O2 nanorods. SEM analysis reveals that Zn incorporation in SnO2 decreases the nanorod diameter from ~20nm to ~10nm. High-resolution x-ray diffraction analysis reveals the rutile structure for x ≤0.04 samples, while for x =0.07 a Zn2SnO4 phase is observed. Near edge x-ray absorption fine structure and x-ray photoemission spectroscopy indicate that Zn atoms have been substituted for Sn sites in SnO2 lattice without forming secondary phases and also create numerous oxygen vacancy in the structure. [Copyright &y& Elsevier]