Band structure of (formula presented) (formula presented) and (formula presented) Angle-resolved photoelectron spectroscopy and ab initio calculations

Abstract

In this work the complete valence-band structure of the molybdenum dichalcogenides (formula presented) (formula presented) and (formula presented) is presented and discussed in comparison. The valence bands have been studied using both angle-resolved photoelectron spectroscopy (ARPES) with synchrotron radiation, as well as ab initio band-structure calculations. The ARPES measurements have been carried out in the constant-final-state (CFS) mode. The results of the calculations show in general very good agreement with the experimentally determined valence-band structures allowing for a clear identification of the observed features. The dispersion of the valence bands as a function of the perpendicular component (formula presented) of the wave vector reveals a decreasing three-dimensional character from (formula presented) to (formula presented) which is attributed to an increasing interlayer distance in the three compounds. The effect of this (formula presented) dispersion on the determination of the exact dispersion of the individual states as a function of (formula presented) is discussed. By performing ARPES in the CFS mode the (formula presented) component for off-normal emission spectra can be determined. The corresponding (formula presented) value is obtained from the symmetry of the spectra along the (formula presented) (formula presented) and (formula presented) lines, respectively. © 2001 The American Physical Society.