Thermovoltage in scanning tunneling microscopy

If the sample and the tip of a scanning tunneling microscope are at differe nt temperatures a 'thermovoltage' arises which is superposed on the externa l bias. Although it is small it can be measured with high accuracy applying scanning tunneling potentiometry. Since it depends on the details of the e lectronic states contributing to the tunneling process it provides useful i nformation, e.g, on interference patterns of electronic surface states, on the distribution of different chemical elements on a surface etc. Results o n homogeneous as well as on inhomogeneous metallic surfaces will be shown. The correlation between the thermovoltage and the electronic states will be discussed for the Si(111) 7X7 surface. (C) 2000 Elsevier Science B.V. All rights reserved.