We have used an ultrahigh vacuum variable-temperature scanning tunneling microscope to study in situ Na intercalation in 1T-VSe2. At room temperature the clean surface showed large flat areas and a trigonal atomic arrangement. Tunneling spectroscopy revealed the known state at 100 mV below E-F. At 60 K the clean surface showed a 4 x 4 charge density wave and the spectra showed a CDW gap Delta approximate to 80 mV. When evaporating less than or equal to 1 ML Na at room temperature, the intercalated Na were distributed non-uniformly, giving bright areas of increased topographic height where Na was intercalated. In the intercalated material the VSe2 state was seen in the tunneling spectra, and was slightly shifted towards E-F. Preliminary spectroscopy of the intercalated material at 60 K showed two different types of spectra. One type showed the VSe2 peak clearly, but had no sign of the CDW gap, while the other type showed a gap structure but did not resolve the VSe2 state. Presently, we can not tell whether these different spectra originate from the differences in the intercalated and non-intercalated areas or not.

We use scanning tunneling microscopy (STM) and core and valence photoemission as well as low-energy electron diffraction to characterize recently discovered S/Cu(111) surface structures that appear at low coverage below ordering temperatures of around 230 K. At even lower coverage ordered local arrangements are observed near steps and dislocations. Of the laterally extending structures one is open. and honeycomb (hc) like, while three other structures (I,II,III) are more complicated. It is suggested that the structures can be explained as reordered (0001) planes of CuS. Surprisingly the open hc structure gives room for the Cu(111) surface state according to photoemission and scanning tunneling spectra. Core level spectra provide support for one of the models proposed for an earlier studied room-temperature structure [Cu(111)-( root 7x root7)R+/-19.1 degrees -S].

We report on the near-field imaging of silver nanoparticles using an aperture-type near-field microscope operated in illumination mode. The nanoparticles are imaged as interference patterns, due to far-field superposition of the optical fields emitted from the tip and elastically scattered from localized surface plasmons (SP). Aperture-type probe can thus be used to obtain information on the phase shift associated with localized SP coupling at the illumination wavelength. (C) 2002 American Institute of Physics.

We present a method for combined far-field Raman imaging, topography analysis and near-field spectroscopy. Surface-enhanced Raman spectra of Rhodamine 6G (R6G) deposited on silver nanoparticles were recorded using a bent fibre aperture-type near-field scanning optical microscope (NSOM) operated in illumination mode. Special measures were taken to enable optical normal-force detection for control of the tip-sample distance. Comparisons between far-field Raman images of R6G-covered Ag particle aggregates with topographic images recorded using atomic force microscopy (AFM) indicate saturation effects due to resonance excitation.