VALENCE-BAND ELECTRONIC-STRUCTURE OF MOS2 AND CS MOS2(0002) STUDIED BY ANGLE-RESOLVED X-RAY PHOTOEMISSION SPECTROSCOPY/

The angle dependence of the valence-band photoemission from the trigon al prismatic layered MoS2 shows both the forward-scattering features n ormally observed in core-level photoelectron diffraction and, in addit ion, the initial-stale orbital character associated with partially occ upied, nonbonding Mo-IV(4d(z)2+-4d(x)2(-y)2 + 4d(xy)) orbitals near th e top of the valence band. The difference in forward scattering betwee n the Mo and S emitters is also used to assess relative contributions from the Mo and S atomic orbitals at specific binding energies within the valence band. Deposition of cesium (0.23 ML Cs with 1 ML equal to the Cs saturation coverage) onto the basal plane of MoS2 introduces a density of states at 1.25 eV above the top of the valence-band maximum . The intensity anisotropy for this Cs-induced valence level is interp reted via the angle dependence of the electric dipole matrix element a s due to the initial-state orbital character at the bottom of the cond uction band of the Cs/MoS2 heterostructure.