Systematic study of chemical bonding states of lithium binary compounds from Li K-L emission spectra obtained by a VUV spectrometer mounted on a scanning electron microscope

The Li K-L emission spectra of lithium metal and its binary compounds (Li3N, Li2O, and LiF) were measured by using a soft X-ray emission spectrometer (SXES), which was equipped with a newly developed high-efficiency diffraction grating (JS35BC) and attached to an electron probe microanalyzer (EPMA). The new grating enables the observation of the entire intensity profile of both Li K-L and Mg L2,3-M emission spectra. The systematic energy shift of the Li K-L spectra to the lower energy side with an increasing electronegativity (or the ionization tendency) of elements of N, O, and F bonded with the Li atom was clearly detected. This shift was reproduced by theoretical calculations and was assigned mainly due to the change of the binding energy of the valence band of those materials. The main peak and its distinct shoulder structure observed in Li K-L spectrum of LiF were assigned as 2p dominated and 2 s + 2p mixed states, respectively, from the comparison with theoretical calculations.