A.S. Soltan

Migration and immobilization of hydrogen and helium in gold and tungsten at low temperatures

Hydrogen, deuterium, and helium were implanted at 5 K with energies from 0.25 to 3 keV into thin films of 80–320 nm of gold and tungsten. The annealing of the implantation‐induced resistivity was measured during isochronally heating of the specimens up to 400 K. The onset of resistivity annealing after implantation to low concentrations was used as indication that the implanted atoms become mobile. The corresponding temperatures were ≤5 K for helium in both metals, ≊18 K for H in Au, ≊50 K for D in Au, and 80 K for H and D in W. The increasing suppression of annealing with increasing concentration of implanted atoms shows that the incomplete annealing above the onset of mobility is mainly due to clustering of implanted atoms and only to a lesser extent due to trapping by impurities.

Optical and Electrical Studies of Se85Te15 Thin Films

The dependence of the optical band gap (E g ) of Se 85 Te 15 thin films on the film thickness and thermal annealing was studied. The value of Eg was found to increase with increasing film thickness. Films annealed at temperatures higher than 353 K showed a decrease in Eg. The effect of the film thickness on the high-frequency dielectric constant (e∞) and carrier concentration (N) was also studied. The effect of thermal annealing on the activation energy for conduction was given and discussed. An amorphous-crystalline transformation in the thin films was observed after annealing at temperatures higher than the glass transition temperature. The crystalline phase resulting from the heat treatment of the as-prepared film was checked by X-ray diffraction observations.

Optical investigation of thermally evaporated Cu5GexTe95−x thin films

Abstract Cu5GexTe95−x (x = 14, 16, 18 and 20) thin films were successfully deposited using thermal evaporation technique. The optical transmittance (T) and reflectance (R) spectra in the wavelength range 250–2500 nm were used for the determination of the optical energy gap and the associated optical constants of the deposited thin films. It was found that, the absorption coefficient (α), refractive index (n) and the extinction coefficient (k) spectra vary with increasing Ge concentration. The indirect optical band gap Eg is found to decrease while the Urbach tail energy increases for different film compositions. The refractive index dispersion data were analysed using the Wemple–DiDomenico single-effective-oscillator model. As a result, the oscillator energy (Eso), dispersion energy (Ed), oscillator strength (Sso), and zero-frequency refractive index (no) were determined. The dependence of the optical constants of Cu5GexTe95−x on the photon energy (hν) at different Ge concentrations is discussed.