The (100) surfaces of alkali halides: I. The air and vacuum cleaved surfaces

Abstract

This paper is the first of a series of three which report the results of studies on the (100) surfaces of LiF, NaF and KCl. The air cleaved and vacuum cleaved surfaces were examined by LEED and Auger emission spectroscopy and the partial pressures of the constituent elements were measured on cleavage of the specimen. Auger analysis of the air cleaved surfaces of LiF and NaF showed the presence of carbon and oxygen, and oxygen was detected on the air cleaved surface of KCl. These impurities could not be detected on the vacuum cleaved surfaces of NaF and KCl but were still observed on the vacuum cleaved surface of LiF. Mass spectrometer studies showed dissociation occurred on cleavage for all three alkali halides although different in character in each case. The form of the partial pressure curves suggests that this dissociation may be non-stoichiometric. LEED patterns obtained from the vacuum cleaved surfaces were of much better quality than those from the air cleaved surfaces except for the case of KCl which gave a poor LEED pattern directly after cleavage but which improved with time.