Scanning tunneling spectroscopy study of adsorbed molecules

TLDR: In this article, the authors used tunneling microscopy and spectroscopy for the detection of trapped molecules of copper phthalocyanine (CuPc) and liquid crystals on graphite.

Abstract: Adsorbed molecules of copper phthalocyanine (CuPc) and liquid crystals on graphite were measured by scanning tunneling microscopy (STM) and spectroscopy (STS) in air. The islands of molecules of CuPc were detected by STM. Tunneling spectra taken simultaneously with STM showed characteristic peaks correlated with local topographic features. In the observation of a nematic liquid crystal on graphite, one reproducible molecular pattern was found, for which a model of molecular ordering is proposed. Ordinary spectroscopy was found to be difficult due to a large polarization current caused by the liquid surrounding the tip. Bias voltage dependent images of the molecules which demonstrate electronic structure effects were obtained.