Atomic corrugation in nc-AFM of alkali halides

The atomic corrugation of alkali halides measured by non-contact force microscopy undergoes strong variations at low-coordinated sites like steps. We present experimental results on structured KBr surfaces and discuss the contrast mechanisms. Chemical sensitivity of the atomic corrugation is demonstrated for a mixed alkali halide crystal

Digital processing of multi-mode nano-mechanical cantilever data

Nanomechanical sensors based on cantilever technology allow the measurement of various physical properties. Here we present a software for the comprehensive analysis of such data. An example for the combined measurement of mass and surface stress is presented

Experimental aspects of dissipation force microscopy

Experimental aspects of measuring dissipation on atomic scale using large-amplitude dynamic force microscopy are discussed. Dissipation versus distance curves reveal that long- and short-range forces contribute to the dissipation. The decay length of short-range contributions is found to be close to that of the tunneling current. The dependence of dissipation on the bias voltage and on the oscillation amplitude is presented. Atomic-scale lateral variations of dissipation are discussed; and the role of the atomic constitution of the tip for quantitative results is pointed out

Ultrathin films of NaCl on Cu(111) : a LEED and dynamic force microscopy study

Ultrathin films of NaCl on Cu(111) have been studied with low-energy electron diffraction (LEED) and Dynamic force microscopy (DFM). The orientation and the lattice constant of the films are revealed by LEED while DFM allows a real space view on their growth modes. The ability of the DFM to image local mechanical surface properties is demonstrated at a substrate step which is covered by a continuous NaCl film

Atomic-resolution images of radiation damage in KBr

The first steps of electron irradiation induced modification of a KBr(1 0 0) surface have been studied by dynamic force microscopy with atomic resolution. Rectangular pits of monatomic depth with not more than one kink site per pit have been found. The atomic structure of KBr(1 0 0) is preserved at the bottom of the pits. Possible deexcitation and desorption mechanisms are discussed based on these results. (C) 2001 Elsevier Science B.V. All rights reserved

Contrast inversion in nc-AFM on Si(111)7 x 7 due to short-range electrostatic interactions

Contrast inversion in nc-AFM on Si(111)7 x 7 is observed at positive sample bias. Corner holes appear as protrusions and adatoms as holes. The application of negative bias voltages causes drastic changes in the atomic constrast. Frequency shift vs distance curves show evidence of short-range, voltage-dependent forces. These observations indicate that short-range electrostatic forces are important for atomic-scale contrast in nc-AFM

Separation of interactions by noncontact force microscopy

Quantitative measurements of frequency shift vs distance curves of ultrahigh-vacuum force microscopy in a noncontact mode are presented. Different contributions from electrostatic, van der Waals, and chemical interactions are determined by a systematic procedure. First, long-range electrostatic interactions are eliminated by compensating for the contact potential difference between the probing tip and the sample. Second, the long-range van der Waals contribution is determined by fitting the data for distances between 1 and 6 nm. Third, the van der Waals part is subtracted from the interaction curves. The remaining part corresponds to the shea-range chemical interaction, and is found to decrease exponentially. A Morse potential is used to fit these data. The determined parameters indicate that the interaction potential between single atoms can be measured by force microscopy in a noncontact mode