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Published online by Cambridge University Press: 01 February 2011
Epitaxial calcium fluoride (CaF2) film surfaces grown on Si(111) were imaged with the atomic force microscopy operated in the noncontact mode in ultrahigh vacuum. Our experimental results reproducibly reveal two kind of topographic patterns with the atomic scale contrast. The line profiles obtained from the topographic image exhibit that the change of tip-polarity plays the important role for obtaining two atomic corrugation patterns by considering the interaction between the tip and the two topmost surface atoms. It is similar to the results from the literature obtained on the cleaved CaF2 surface with both positively and negatively terminated tip.