Large modulation-amplitude, local barrier-height, scanning tunneling microscopy

We compare and contrast both STM topographic images and local tunneling barrier-height (LBH) spatial distributions using relatively large modulation of the tunneling gap. Measurements were carried out on various surfaces including Si(111)-(7 × 7), Ge(111)-(3 × 1)-Na, Si(111)-(√3 × √3)-Sn. The experimental results of the local barrier-height obtained in this way are dependent on the tip-sample distance indicative of strong tip-sample interaction. The large modulation LBH method senses the "hardness" of the tip surface interaction potential, which varies with lattice position. Both methods, STM topographic images and local barrier-height images, provide complementary, but different information, to check the consistency of structural conclusions.