BARRIER-HEIGHT IMAGING OF OXYGEN-ADSORBED SI(111) 7X7 SURFACES

Barrier-height imaging with scanning tunnelimg microscopy (STM) is app lied to the study of oxygen adsorption on a Si(lll) 7 x 7 surface. On clean surfaces, atomic resolution is obtained in the barrier-height mo de, as expected for corrugated surfaces. Upon exposure to oxygen, the barrier height phi is found to increase at the oxygen-reacted sites. T he dark sites show a greater increase in phi than the bright sites, in dicating more charge transfer at the dark sites.