Resistivities, carrier concentrations, optical absorption, and photoluminescences of undoped and Cd,Zn-doped CuAlSe2 single crystals grown by chemical vapor transport were studied. The electrical and optical properties were almost unchanged after annealing under Se pressure. However, the resistivity increased about seven orders of magnitude after annealing in vacuum. The resistivity also increased by Cd or Zn doping. The samples showed p-type conduction even when Cd or Zn was doped. An acceptor ionization energy of about 65 meV was obtained. The mobility showed the dominance of lattice scattering for temperatures between 80 and 200 K. Two independent, broad, red luminescences having their own excitation energies were observed at relatively low temperature. We have proposed the configuration coordinate model for this characteristic emission. The emission can be interpreted as radiative transitions from a deep center to the respective A or C valence bands, accompanied by a lattice relaxation.
High-temperature annealing of semi-insulating GaAs has been studied. Thermal conversion induced by annealing at 1060–1200 °C can be explained by the causes of both the reduction of EL2 concentration and the generation of deep acceptors during high-temperature annealing. Both of them can be rationalized by the supposition that the antisite defect, AsGa, breaks into AsI and VGa, and the latter is a deep acceptor.
Circularly polarized luminescence (C.P.L.) spectroscopy has been recently accepted as a unique technique which detects a difference in intensities between left- and right-circularly polarized emission and thereby elucidates chirality of optical active molecules in the emitting state[1]. This spectroscopic means is complementary to circular dichroism(CD) spectroscopy in which information in the ground state is obtained. We have been interested in studying vicinal effects of chiral rare earth cmoplexes by CPL spectroscopy[2]. In order to investigate conformational and configurational effects, we have extended our work to tris chelate chromium (III) complexes of D3 symmetry. Since chiral fluorescent molecules are easily damaged by photolysis, we have also constructed a very sensitive and stable digital instrument based on an Apple II microcomputer for the measurements of CPL spectra.
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