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. q1999 Elsevier Science B.V. All rights reserved