SIMULATION OF SCANNING TUNNELING MICROSCOPE IMAGE BASED ON ELECTRONIC STATES OF SURFACE TIP SYSTEM

Scanning tunneling microscope images of graphite are calculated taking into account microscopic electronic structure of tip. As a model tip with [111] protrusion, a W10cluster is used. Electronic states of surface and tip are calculated non-empirically and are combined to obtain the tunnel current. When all the tip levels contribute to tunneling, normal images of graphite are obtained, which change from triangular to honeycomb lattice by increasing the bias. In the case that special tip levels are active in tunneling, anomalous images such as linear-chain type are obtained. It is shown that anomalous images are not necessarily multitip effect. By varying the applied bias, conductance spectrum is also calculated and is compared with experimental one. © 1990, American Vacuum Society. All rights reserved.