The Fundamental Optical Absorption and the Valence Bands in Alkali Cuprous Halide Crystals

Abstract

In K 2 CuCl 3 and K 2 CuBr 3 crystals, the fundamental optical absorption has been found to be at about 4.5 eV from the reflectivity measurement. An intrinsic luminescence band due to a forbidden transition has been found at about 3.2 eV in both crystals. From the observation of the X-ray photoelectron spectrum, a conclusion is drawn that the top of the valence band is the d-band of the curprous ion. The properties of the fundamental absorption and the luminescence are consistent with this conclusion.