Surface defects of KBr produced by electron irradiation

Low energy electron loss spectra (LEELS) of KBr single crystals and films were measured at several temperatures from room(RT) to liquid nitrogen temperatures(LNT). For single crystals, four loss peaks at 2.05(A), 1.65(B), 1.30(C) and 1.00(D)eV were observed at -140degC and at 2.05(A), 1.65(B) and 0.5(E)eV at LNT in the band gap region where no loss peaks were observed at RT. Among them, the loss peak at 2.05 eV is ascribed to the bulk F-centers, and other three peaks are to defects at crystal surfaces produced by electron irradiation. For evaporated films, only three lower loss peaks, B, C and D were observed. Because evaporated films are polycrystaline and have large surface area, it is thought that LEELS show only loss peaks due to surface defects. (author)