Photothermal effects induced by laser excitation in a scanning tunneling microscope

Numerous near-field experimental methods use laser excitation inducing non- negligible thermal effects that are not taken into account. We particularly investigate the case of a scanning tunneling microscope, The analysis of t he experimental results gives the thermal contribution of the probe in the measured signal when the probe is irradiated by the laser beam. The phase o f the signal allows the distinction between the effects induced by the prob e and the sample. We show that the experimental set-up can measure the peri odic thermal expansion of the sample with the picometer resolution. (C) 200 0 Editions scientifiques et medicales Elsevier SAS.