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Evolution of structure and properties in ternary Ag2Te1−xSex (x~0.3) alloy is examined in the present paper. Stoichiometric quantity of pure powders of Ag2Te and Ag2Se was mixed in a ball mill and then melted at high temperature, 1025°C in a vacuum sealed quartz tube, followed by annealing at 700°C for 12 hours. Thin films of Ag2Te.7Se.3 of different thickness viz.25, 50, 100, and 150 nm are produced by thermal evaporation method. Thermal evaporation method is carried out by resistive heating of the solid of Ag2Te.7Se.3 sample at 1000°C under a high vacuum (pressure in the chamber is less than 10−5 mbar). The thin films were subjected to structural analysis by XRD, microstructural study by scanning electron microscopy and optical property study by UV-Vis. spectroscopy. It is found that Ag2Te1−xSex (x~0.3) is formed by alloying of two solid solutions, of which one is based on Ag2Te with Se as solute and the other is Ag2Se-based solid solution in which Te is the solute. The peak position of Ag2Te-based solid solution is shifted toward higher angle whereas a reverse trend is observed in Ag2Se-based solution. The microstructure is composed of a solid solution of Ag2Te and Ag2Se along with the fine dispersion of elemental silver, tellurium and selenium. The optical band gap varies within 1.4 to 2.2 eV over the thickness range from 25 to 150 nm. The band gap initially increases with the film thickness, and beyond 50 nm, the band gap continuously decreases to 1.7 eV. The transmittance is lower for higher film thickness; while transmittance increases with wavelength, the rate of increase is enhanced in the infrared region. The absorption coefficient of thin films of Ag2Te.7Se.3 is as high as of the order of 105 cm−1. [ABSTRACT FROM AUTHOR]

Thin film-based thermoelectric materials have attracted enormous research interest due to their potential to exhibit excellent thermoelectric (TE) behavior. Considering the potential of earth-abundant and nontoxic magnesium silicide (Mg2Si) to behave as a mid-temperature TE material, the present study was conducted to assess the structural evolution and electrical behavior of Mg2Si films prepared by electron beam thin film deposition technique. The films were deposited on silicon (100) substrate at room temperature with thickness ranging from 0.5 µm to 4 µm. The investigation revealed that the electrical behavior of this alloy film is considerably influenced by its thickness. The effect of film thickness on evolution of the structure was also studied by x-ray diffraction (XRD), field emission scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. It was observed that the present experimentation could produce a nanocrystalline grain structure of Mg2Si alloy with a small quantity of excess magnesium phase. Moreover, XRD results delineated that the crystallite size is influenced by the thickness of the film under the same deposition conditions. The residual stress within the e-beam-deposited film, as manifested through the measured strain values of the films, was found to be thickness-dependent. Moreover, it was confirmed that there was no influence of the substrate on the structure and properties of the studied films. [ABSTRACT FROM AUTHOR]