NA INTERCALATION OF VSE2 STUDIED BY PHOTOEMISSION AND SCANNING-TUNNELING-MICROSCOPY

In situ Na intercalation of the layered compound VSe2 has been studied with photoemission and scanning tunneling microscopy. Core-level spec troscopy proves that Na deposited in UHV onto the VSe2 surface rapidly intercalates, leaving only small amounts at the surface. The scanning tunneling microscopy measurements show that the intercalated Na is no t uniformly distributed between the VSe2 layers, but preferentially in two-dimensional islands. Thus the surface region is divided into inte rcalated and nonintercalated areas. Hole-like features in the intercal ated areas are interpreted as locally missing Na.