Scanning Tunneling Microscopy and Atomic Force Microscopy Investigations on Organic Material Thin Films and Adsorbate Particles in Air

Abstract

We present investigations on polycrystalline thin films of TCNQ and of metal-phthalocyanines as well as of metal-polymer composite material films by scanning tunneling and atomic force microscopy at ambient conditions. The influences of preparation conditions (usual thermal evaporation in high vacuum) as well as external influences such as applied external pressure on the crystallite morphology, surface topography and imaging conditions are discussed. Using a liquid cell in an atomic force microscope, we have been able to resolve the molecular structure of copper- and of leadphthalocyanine crystals. For rough surfaces as discussed above the influence of the mesoscopic tip shape has to be taken into account. We report on theoretical modelling as well as on experimental efforts related to STM imaging using proper tips. In the case of ultrathin organic films, there is often the problem of fixing the molecules to the substrate. We show that in this case after some rather harsh sweeping by the tip, one can observe fairly ordered molecular structures near to the lower part of surface steps on layered material substrates.