Surface processes on KBr single crystals examined by thermostimulated exo-electron emission and desorption

Abstract

Potassium bromide (KBr) is a material with many potential uses in various branches of physics and technology (in scintillators, for a Fourier spectrometer, electro-optical elements such as IR laser windows, sensors and optical fibers). We conducted a series of combined measurements of thermally stimulated exo-electron emission (TSEE) and thermally stimulated desorption (TSD). At low doses of UV irradiation, the most prominent process is the combined emission of negative charges with desorption of the components of O, H2O and mainly K, KOH and Br, as described below. At higher irradiation doses, the KBr F-center plays the most important role (Tm = 160 °C) and at temperatures above +200 °C also the decomposition of chemically bonded atoms and other components occurs. This process is accompanied by the corresponding emission of electrons and at the same time some of the already chemically bonded structures such as HBr3 are released. TSD maxima are defined and the same temperature maxima for TSD and TSEE are shown, mainly at the already mentioned higher temperatures. These maxima are linked to the defects and interactions in the surface layer. The obtained results fully confirm the applicability of our apparatus for combined measurements of TSD, TSEE, thermally stimulated luminescence (TSL) and possibly also thermally stimulated conductivity (TSC).