Scanning tunneling spectroscopy analysis with a triangular inverse transfer matrix and its application to reduced SrTiO3 (110) surface

A straightforward method to deduce sample local density of states (LDOS) from the current-voltage characteristics (I-V) raw data in scanning tunneling spectroscopy (STS) is presented. The method is based on the relation between the I-V spectrum and the LDOS, both of which are treated as one-dimensional vectors: the I-V is generated from the LDOS by operating a triangular transfer matrix M. Then the LDOS is readily calculated from the I-V by operating the inverse matrix M-1, Which is also triangular. The method is an alternative for the conventional method to take (dl/dV)(VII), which often causes artificial peaks in LDOS at the onsets of I-V. Each row of M is determined by the tip density of states (DOS) and the barrier profile for the corresponding bias voltage. The tip DOS will be calculated from the I-V values measured at different tip-to-sample distances if the tip and sample have the same DOS and the barrier profile is symmetrical. As an example, the LDOS is calculated for the reduced SrTiO3 (110) on which the electronic states show metallic character depending on the annealing condition and sites. (C) 2001 Elsevier Science B.V. All rights reserved.