Noncontact AFM imaging on Al-adsorbed Si 111/ surface with an empty orbital

Force interaction between an orbital of dangling bond out of an Si tip apex and an empty orbital on Al-adsorbed Si 111. surface is investigated to clarify the imaging mechanism of noncontact atomic force microscopy AFM.. Very strong contrast of noncontact AFM image is obtained. The characteristic discontinuity in the distance dependence of the frequency shift is also observed, which originated from chemical bonding interaction. This means that the force interaction between an orbital of dangling bond out of tip apex and an empty orbital of Al-adsorbed Si 111.surface strongly contributes to the image contrast. q2000 Elsevier Science B.V. All rights reserved.