Imaging and spectroscopy of nanostructured surfaces

[摘要] STM measurements of large size selected clusters of Pd on HOPG show that the aspect ratio increases with increasing cluster size. The non-spherical nature of these clusters is traced back to the aggregation regime in the gas condensation cluster source. The size and temperature of the clusters create a slow coalescence process that leads to non-spherical clusters. The molecule methylphenyldisulphide is studied on Si(111)-7x7 by STM. The molecule is found to bond either as an intact molecule or as fragments after fission of the disulphide bond upon landing. The molecule exhibits a 2:1 preference for the middle adatom of the 7x7 unit cell suggesting it enters a precursor state before adsorbing on the surface. The new SPEAR technique uses an STM tip to collect photoelectrons generated at a surface. The detection of a photocurrent with a W tip is demonstrated. In the case of a bare HOPG surface electronic states of the tip are resolved. However, the large signal generated by photoelectrons from the tip restricts the resolution of states of the surface. To resolve spectra on the nanometre scale a coaxial tip is required, this is demonstrated through the use of simulations.

[发布机构] University:University of Birmingham;Department:School of Physics and Astronomy

[关键词] Q Science;QC Physics