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Noncontact lateral-force gradient measurement on Si(111)-7 x 7 surface with small-amplitude off-resonance atomic force microscopy

Atabak, Mehrdad
Unverdi, Ozhan
Özer, Hakkı Tunçay
Oral, Ahmet
In this work, the authors report on a quantitative investigation of lateral-force gradient and lateral force between a tungsten tip and Si(111)-(7 x 7) surface using combined noncontact lateral-force microscopy and scanning tunneling microscopy. Simultaneous lateral-force gradient and scanning tunneling microscopy images of single and multiatomic step are obtained. In our measurement, tunnel current is used as feedback. The lateral-stiffness contrast has been observed to be 2.5 N/m at a single atomic step, in contrast to 13 N/m at a multiatomic step on Si (111) surface. They also carried out a series of lateral stiffness-distance spectroscopy, which show a sharp increase in tip-surface interaction stiffness as the sample is approached toward the surface. (C) 2009 American Vacuum Society. [DOL 10.1116/1.3097857]