Unoccupied electron states in low-energy electron total-current and transmission spectroscopy of molybdenum disulfide

A theoretical interpretation of the fine structure in the low-energy electron total-current spectra and low-energy electron transmission spectra measured along the normal to the (0001)MoS2 single-crystal surface is proposed. The calculations took into account the energy dependence of band level broadening and the electronic structure of the high final unoccupied states (above the vacuum level E-vac), which become occupied by electrons entering a solid. A comparison with the available experimental and theoretical data is performed. The effects of the bulk band structure are shown to play a dominant role in the formation of the spectra (the extrema in the spectra identify the energy position of critical points, such as the band edges or the points of extremal curvature of the dispersion branches). The proposed method makes it possible to separate the bulk effects in spectra from surface effects, this approach can be used to advantage in monitoring the state of a surface in the course of its treatment. (C) 2003 MAIK "Nauka / Interperiodica".