The electronic structure of transition metal interacting tip and sample and atomic force microscopy. II

For pt. I see ibid., vol. 7, p. 6625 (1995). A detailed theoretical study of the interaction of transition metal nanotips with surfaces is performed in the tight-binding scheme. The real space recursion method is used to determine the local densities of states (LDOS) of the interacting tips and samples. We consider more especially W supported pyramidal tips with different morphologies. The interaction of W supported tips with W(001) surfaces is studied within the intermediate-interaction regime for which metallic adhesive forces are dominant. The electronic structure of both the tip and the sample are found to be substantially modified due to the tip/sample (T/S) interaction. The T/S interaction energy curves are also calculated when the tip's apex is located above high-symmetry surface sites. It is shown that the T/S interaction energy can be reproduced with a good accuracy using the model of a square LDOS. Finally, we present a simple numerical scheme to obtain atomic force images. We study the influence of the tip's morphology and of the surface's defects on the contrast of the resulting images.