In this study, the corrosion properties of Zn-Co alloys prepared by the electrodeposition method from a sulfate bath under potentiostatic conditions on steel and aluminum substrates have been investigated. The deposit morphology and elemental composition were examined by scanning electron microscopy (SEM)/EDX. The preferred crystallographic orientations of the deposits have been determined by the x-ray diffraction (XRD) technique. The effects of bath composition on the phase structure, morphology and corrosion behaviors have been studied. It has been observed that the cobalt content strongly affects the structure and corrosion stability of Zn-Co alloys. It was found that amorphous alloys were obtained with high Co contents, while crystalline alloys were formed with high Zn contents.

N-implantation to GaSe single crystals was carried out perpendicular to c-axis with ion beam of 6x10 15 ions/cm 2 dose having energy values 30 keV and 60 keV. Temperature dependent electrical conductivities and Hall mobilities of implanted samples were measured along the layer in the temperature range of 100-320 K. It was observed that N-implantation decreases the resistivity values down to 10 3 Ω-cm depending on the annealing temperature, from the room temperature resistivity values of as-grown samples lying in the range10 6 -107 Ω-cm. The temperature dependent conductivities exhibits two regions (100-190 and 200-320 K) with the activation energies of 234-267 meV and 26-74 meV, for the annealing temperatures of 500 and 700 °C, respectively. The temperature dependence of Hall mobility for the sample annealed at 500 °C shows abrupt increase and decrease as the ambient temperature increases. The analysis of the mobility-temperature dependence in the studied temperature range showed that impurity scattering and lattice scattering mechanisms are effective at different temperature regions with high temperature exponent. Annealing of the samples at 700 °C shifted impurity scattering mechanism toward higher temperature regions. In order to obtain the information about the defect produced by N-implantation, the carrier density was analyzed by using single donor-single acceptor model. We found acceptor ionization energy as E a =450 meV, and acceptor and donor concentration as 1.3x10 13 and N d =3.5x10 10 cm -3 , respectively.

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GaSe single crystals grown by Bridgman method have been doped by ion implantation technique. The samples were bombarded in the direction parallel to c-axis by Si ion beam of about 100 keV to doses of 1x10 16 ions/cm 2 at room temperature. The effects of Si implantation with annealing at 500 and 600 o C on the electrical properties have been studied by measuring the temperature dependent conductivity and photoconductivity under different illumination intensities in the temperature range of 100-320 K. It is observed that Si implantation increases the room temperature conductivity 10 -7 to 10 -3 (Ω-cm) -1 depending on the post annealing temperature. The analysis of temperature dependent conductivity shows that at high temperature region above 200 K, the transport mechanism is dominated by thermal excitation in the doped and undoped GaSe samples. At lower temperatures, the conduction of carriers is dominated by variable range hopping mechanism in the implanted samples. Annealing of the samples at and above 600 o C weakens the temperature dependence of the conductivity and photoconductivity. This indicates that annealing of the implanted samples activates Si-atoms and increases structural deformations and stacking faults. The same behavior was observed from photoconductivity measurements. Hence, photocurrent-illumination intensity dependence in the implanted samples obeys the power low I pc ∝ Φ n with n between 1 and 2 which is an indication of continuous distribution of localized states in the band gap.

Optical anisotropy of the layer semiconductor GaSe has been studied by photoluminescence (PL) and Fourier Transform Infrared Spectroscopy (FTIR). The PL spectra are dominated by two closely positioned emission bands resulting from the free exciton and the bound exciton connected direct band edge of GaSe. Photoluminescence and transmission spectra of GaSe crystals have been measured for two cases in which the propagation vector k is perpendicular (k⊥c) and parallel to the c-axis (k//c). Peak position of the PL emission band and the onset of the transmission have been found to be significantly different for these two cases. This observed anisotropy is related to anisotropic band structure and the selection rules for the optical absorption in layered GaSe. FTIR transmission spectrum is in good agreement with PL results.