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

Abstract

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 (d I /d V )( V / I ), 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 SrTiO 3 (110) on which the electronic states show metallic character depending on the annealing condition and sites.