%e report the observation of Raman scattering associated with the vibrational modes in the diluted magnetic semiconductor Znl "Mn, Te. The low-frequency two-phonon density-of-states features in Znl "Mn"Te, similar to those of ZnTe, exhibit composition-dependent Raman shifts. Lawfrequency disorder-induced one-phonon density-of-states features are also present in the Raman spectra for x &0.10. The optical phonons of Znl "Mn"Te exhibit a variation with x that is intermediate between the two-mode and one-mode situations. The optical mades af Znl "Mn"Te are compared with those of Cdl "Mn"Te, the prototype of wide-band-gap diluted magnetic semiconductors. A random-element isodisplacement model is used ta describe the behavior of the optical phanons of both alloy systems.

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The photoelectrochemistry of n-CuInS2 and CuInSe2 in polysulfide electrolyte is studied with particular emphasis on the pretreatments of the electrodes and on their output stability. The use of Cd doping, (photoelectro)chemical etching, and mild air oxidation all were found to improve electrode performance. The effect of air oxidation was reproducible only for the diselenide, where it improved the fill factor and, because of a negative shift of the flatband potential, the open-circuit voltage. Optimized cells showed, at elevated temperatures, conversion efficiencies around 5 and 7.5% for the sulfide and selenide, respectively. The positive temperature dependence of the photo-I-V characteristics at both low and high illumination intensities, the existence of optimal polysulfide solution compositions, the linear dependence of the photocurrent on the light intensity, and the effects of temperature, solution composition, and initial current density on the photocurrent decrease during the first minute of operation of the cells, are ascribed to limitations of the charge-transfer process across the solid/liquid interface. Thermally activated rates of ad-and desorption of sulfur containing solution species on the semiconductor surface and/or the presence of adsorption-induced electronic states in the bandgap are postulated as causes for this behavior. Notwithstanding these limitations the cells are resistant to photocorrosion, after the initial decrease is arrested, in contrast to what is known for similar Cd-chalcogenide-based systems. We suggest that this stability, which persists under load and at high light intensities, is due to the strength and character of the bonds in CuIn-dichalcogenides, or to the presence of a top layer of indium oxide in which recombination will take place, or to both.

The optical absorption, photoconductivity, contact photovoltage, electrical conductivity, and Hall coefficient of single crystals of WSe2 have been studied over the temperature range 77°–295°K. It was found that the forbidden energy gap Eg was 1.35 eV at 295°K and that the temperature dependence of Eg was given by dEg/dT=−4.6×10−4 eV/°K. The material as grown by iodine vapor transport in a sealed ampule is p-type with hole mobility μh∼80 cm2/V·sec and p∼1016/cc at 295°K. The carrier concentration could be reduced by pumping out excess selenium. Doping with rhenium during the crystal growth process resulted in n-WSe2 with a carrier concentration n∼1017/cc and electron mobility μn∼100 cm2/V·sec at 295°K.