On the interpretation of current images in scanning tunneling spectroscopy of Si(111)7×7

During scanning of Si(111)7×7 the tunneling current has been determined at every tip position as a function of bias voltage keeping the distance between tip and sample at a constant value by stabilization of the tunneling current for only a small time interval. For positive (2 V) and negative (−2 V) stabilization voltage we have obtained two sets of current images. Our results show that the hitherto neglected energy-dependent transmission probability on the tunneling current and the intimate relation between electronic and topographic properties prevent a simple determination of the local density of states.