Papers by Author: T.G. Kryshtab

Abstract: Bi-Pb-Sr-Ca-Cu-O (BPSCCO) and Bi-Pb-Sb-Sr-Ca-Cu-O (BPSSCCO) thin films were grown on MgO single crystal substrates by pulsed laser deposition. The deposition was carried out at room temperature during 90 minutes. A Nd:YAG excimer laser ( = 355 nm) with a 2 J/pulse energy density operated at 30 Hz was used. The distance between the target and substrate was kept constant at 4,5 cm. Nominal composition of the targets was Bi1,6Pb0,4Sr2Ca2Cu3O and Bi1,6Pb0,4Sb0,1Sr2Ca2Cu3OSuperconducting targets were prepared following a state solid reaction. As-grown films were annealed at different conditions. As-grown and annealed films were characterized by XRD, FTIR, and SEM. The films were prepared applying an experimental design. The relationship among deposition parameters and their effect on the formation of superconducting Bi-system crystalline phases was studied.

Abstract: The structural characteristics of Au-TiB ₂/GaAs and Au-Mo-TiB₂-AuGe/GaAs device structures after deposition and short-term thermal annealing (STTA) were investigated. The multilayer contacts with TiB₂ anti-diffusion layer were magnetron sputtered on (001) GaAs substrates. The structures were STTA in a stream of hydrogen at temperatures of 400°C, 600°C, and 800°C during 60 seconds. The X-ray diffraction techniques and atomic force microscopy were used for investigation. At STTA a reduction of residual strain in multilayer metallic films, an increment of film grain size, a change of grains preferred orientation in the Au polycrystalline film and a transformation of surface morphology of the upper Au film were observed. These processes do not have monotonic temperature dependence. For Au-TiB₂/GaAs a minimum value of residual strains was observed at T=600°C while for Au-Mo-TiB₂-AuGe/GaAs it was observed at T=400°C. The roughness of Au film monotonically increased at annealing of Au-TiB₂/GaAs structure at T=400°C and T=600°C and corresponded to the initial value at T=800°C. A strong change of Au film roughness was observed at annealing of Au-Mo-TiB₂-AuGe/GaAs structure at T=600°C. The XRD pattern from a Au-TiB₂ metal film denoted a quasi-amorphous structure in the initial state and an increment of micrograins size at STTA. In the initial state the crystalline structure of Au film in Au-Mo-TiB₂-AuGe/GaAs structure had some preferred orientation in the <111> direction, which was reduced after STTA at T=600°C. The polycrystalline structure of Au film was partially deteriorated after STTA at T=800°C as TiB₂ layer was destroyed and lost its diffusion protecting properties.