Laser-Assisted Scanning Tunneling Microscopy Studies of Thin Ordered Molecular Layers

Abstract

The irradiation of the junction of an STM with laser light may give access to the study of resonant effects. Since high laser intensities are required, an active compensation setup, designed to suppress the dominating nonresonant effects is used. Mixed films of the dye perylene-tetracarboxylic-dianhydride (PTCDA) and the liquid crystal octylcyanobiphenyl (8CB) were prepared on graphite and MoS2. STM measurements show small isolated domains of PTCDA embedded in 8CB. The islands could be imaged with high resolution even under the illumination with intense laser light. First experiments investigating the laser-induced contrast observed on the dye islands under active compensation of the nonresonant effects are discussed.