Electronic structure of non-centrosymmetric AgCd2GaS4 and AgCd2GaSe4 single crystals

Abstract

X-ray photoelectron core-level and valence-band spectra for pristine and Ar+-ion irradiated (001) surfaces of AgCd2GaS4 and AgCd2GaSe4 single crystals grown, respectively, by the Bridgman method and the method of direct crystallization have been measured in the present work. The X-ray photoelectron spectroscopy (XPS) results reveal high chemical stability of (001) surfaces of AgCd2GaS4 and AgCd2GaSe4 single crystals. Electronic structure of AgCd2GaS4 has been calculated employing the full potential linearized augmented plane wave method. For the AgCd2GaS4 compound, the X-ray emission bands representing the energy distribution of the valence Ag d-, Cd d-, Ga p- and S p-like states were recorded and compared on a common energy scale with the XPS valence-band spectrum. The theoretical and experimental data regarding the occupation of the valence band of AgCd2GaS4 were found to be in excellent agreement to each other. Second harmonic generation (SHG) efficiency of AgCd2GaS4 by using the 320ns CO laser at 5.5μm has been recorded within the temperature range 80–300K. Substantial increase of the photoinduced SHG which in turn is substantially dependent on the temperature has been detected for the AgCd2GaS4 compound.