SPECTROSCOPIC RESPONSE OF PHOTOINDUCED CURRENTS IN A LASER-ASSISTED SCANNING TUNNELING MICROSCOPE

Thermal expansion of the sample or tip in a laser-assisted scanning tu nneling microscope (STM) junction can obstruct the study of other phen omena related with STM-light interactions, when photoinduced currents are analyzed. In this article, we show that the thermal contribution i s proportional to the average tunneling current and that this can be u sed to distinguish it from other contributions. Simultaneous tunneling current-voltage and photoinduced current-voltage curves are recorded for highly oriented pyrolitic graphite and gold samples with a Pt tip. We have done the measurements for two different polarizations of the incident beam. We show that the I-V curves can be used to discriminate between different mechanisms that appear, producing photoinduced curr ents. (C) 1997 American Institute of Physics. [S0021-8979(97)05021-4].