title: Atomic contact potential variations of Si(111)-7 x 7 analyzed by Kelvin probe force microscopy.
abstract: We studied atomic contact potential variations of Si(111)-7 x 7 by Kelvin probe force microscopy with the amplitude modulation technique at the second resonance of a silicon cantilever. Enhanced sensitivity due to the high mechanical quality factor in ultra-high vacuum enabled local contact potential difference (LCPD) measurements of individual adatoms. The contrast of the measured LCPD map became stronger by reducing the tip-sample distance, and the averaged LCPD value shifted to more negative. The short-range interaction, arising from the covalent bonding interactions, strongly affects the LCPD measurement. Theoretical calculations indicate that the amplitude modulation method has a higher sensitivity than the frequency modulation method in practical cases. The tip-sample distance dependence of LCPD was investigated by numerical calculations.
authors.affiliation: EMPA, Swiss Federal Laboratories for Materials Testing and Research, Uberlandstrasse 129, 8600 Dübendorf, Switzerland. shigeki.kawai@unibas.ch
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kawai
authors.forename: Thilo
authors.initials: T
authors.lastname: Glatzel
authors.forename: Hans-Josef
authors.initials: HJ
authors.lastname: Hug
authors.forename: Ernst
authors.initials: E
authors.lastname: Meyer