ANALYSIS AND COMPENSATION OF THERMAL EFFECTS IN LASER-ASSISTED SCANNING TUNNELING MICROSCOPY

As an indispensable step towards detection of selective, resonant light absorption in laser-assisted STM, we analyzed the thermal expansion produced by laser irradiation of the tunneling junction. The expansion as a function of the modulation frequency of the light power could be related to the specific heat and thermal conductivity of the materials involved. A scheme is presented, aiming for detection of small tunneling current changes induced by resonant optical excitation of an adsorbate. It is based on the idea of irradiating the tunneling gap with two laser beams of different wavelengths-only one being in resonance with the adsorbate-and suppressing the thermal contribution to the tunneling current by an amplitude modulation of both beams with a 180-degrees phase shift.