Microstructure and mechanical properties of copper subjected to high pressure torsion

Experiments were conducted on copper subjected to High Pressure Torsion to investigate the evolution of microstructure and microhardness with shear strain, gamma. Observations have been carried out in the longitudinal section for a proper demonstration of the structure morphology. An elongated dislocation cell/subgrain structure was observed at relatively low strain level. With increasing strain, the elongated subgrains transformed into elongated grains and finally into equiaxed grains with high angle grain boundaries. Measurements showed the hardness increases with increasing gamma then tends to saturations when gamma >5. The variation tendency of microhardness with gamma can be simulated by Voce-type equation.

Optical parameters and absorption of copper (II)-azo complexes thin films as optical recording media

Smooth thin films of three kinds of azo dyes of 2-(5'-tert-butyl-3'-azoxylisoxazole)-1, 3-diketones and their copper (II)-azo complexes were prepared by the spin-coating method. Absorption spectra of the thin films on a glass substrate in the 300-600 nm wavelength region were measured. Optical constants (complex refractive index N=n+ik) and thickness of the thin films prepared on single-crystal silicon substrate in the 300-600 nm wavelength region were investigated on rotating analyzer-polarizer type of scanning ellipsometer, and dielectric constants epsilon(epsilon=epsilon(1)+i epsilon(2)), absorption coefficients alpha as well as reflectance R of thin films were then calculated. In addition, one of the copper (II)-azo complex thin film prepared on glass substrate with an Ag reflective layer was also studied by atomic force microscopy (AFM) and static optical recording. AFM study shows that the copper (II)-azo complex thin film is very smooth and has a root mean square surface roughness of 1.89 nm. Static optical recording shows that the recording marks on the copper (II)-azo complex thin film are very clear and circular, and the size of the minimal recording marks can reach 200 nm. (c) 2004 Elsevier B.V. All rights reserved.

PASSIVATION OF COPPER BY LITHIUM IN P-TYPE GAAS

We report the passivation of two deep copper-related acceptor levels in Cu-diffused p-type GaAs by the group-I element lithium. The deep-level-transient-spectroscopy (DLTS) signals of the well-known Cu-related levels with apparent activation energies 0.15 eV and 0.40 eV disappear in Cu-diffused samples when they are diffused with Li, but can be reactivated by annealing. Photoluminescence measurements show a corresponding disappearance and reappearance of the copper-related luminescence at 1.36 eV. Also we observe with DLT'S an energy level at E(V) + 0.32 eV in the Cu-Li-diff-used samples. The level is neither present in the Cu-diffused samples before Li diffusion nor in Cu-Li-diffused samples after annealing. As the level is not observed in starting materials or solely Li-diffused samples we suggest that it is related to a Cu-Li complex.