An atomic-scale study was made of in situ cleaved (110) surfaces, in the dynamic scanning force microscopy mode, at low temperatures. On defect-free surfaces, the dynamic-mode images always exhibited strong maxima above the As-atom positions, where the total valence charge density was greatest. In the case of certain tips, the In atoms also became visible but their appearance depended strongly upon the specific tip-sample interaction. Protrusions as well as depressions were observed at the positions of the In atoms. An investigation was also made of the appearance and nature of 2 different types of atomically resolved point defect. The most frequently observed point defect was seen as a missing protrusion; thus indicating the existence of an As vacancy. A second type of observed point defect was probably an In vacancy. This was detected indirectly via its effect upon the 2 neighboring As atoms at the surface. At large tip-sample distances, these As atoms exhibited reduced corrugations, as compared with the surrounding lattice. At smaller tip-sample distances, the corrugation was increased. This distance-dependent contrast inversion was explained in terms of relaxation, of the As atoms above the defect, which was produced by an attractive tip-sample interaction.

Dynamic-Mode Scanning Force Microscopy Study of n-InAs(110)-(1 x 1) at Low Temperatures A.Schwarz, W.Allers, U.D.Schwarz, R.Wiesendanger: Physical Review B, 2000, 61[4], 2837-45