Microscopical analysis of structure and work function of Ba-covered Si(111)-(7×7) surface

Microscopic `work function' is evaluated by local tunneling barrier height (LBH) measurements of clean and Ba-deposited Si(111) surfaces in order to clarify the mechanism of work function reduction by Ba deposition. Atomically resolved LBH images are obtained corresponding to scanning tunneling microscopy (STM) images. The difference in the LBH measurement for clean Si(111)-(7×7) and Ba deposited Si(111)-(3×1) surfaces agrees with macroscopic work function reduction due to Ba adsorbate. The result suggests that the work function is strongly related to the atomic arrangement of the Si(111) surface induced by Ba deposition.