DETERMINING UNOCCUPIED BANDS OF LAYERED MATERIALS BY VLEED - IMPLICATIONS FOR PHOTOEMISSION BAND MAPPING

We report VLEED/TCS measurements on the layered transition metal dicha lcogenide VSe2. By combining the experimental results with simple VLEE D calculations, we have been able to determine the unoccupied bands co nstituting the upper bands in photoemission. Our analysis reveals accu rate positions of so-called coupling bands, which predominantly contri bute to both electron transmission and photoemission. Better knowledge about these bands may substantially improve the accuracy of valence b and mapping, particularly in studies of layered materials like VSe2, a s the upper bands of these are too complicated to be well approximated by free-electron-like bands. We discuss in some detail the connection between VLEED and photoelectron spectroscopy, and we obtain for the f irst time a detailed recipe for k(perpendicular to)-resolved band mapp ing, with utilization of VLEED results. Some previous photoemission re sults are reexamined in the light of our present findings, and the pow er of combined VLEED/photoemission studies is stressed.