Diamond tips in low temperature scanning tunneling microscopy

Scanning tunneling microscopy and ballistic electron emission microscopy me asurements are presented using boron-doped diamond as tip material. The exp eriments were carried out at 77 K on CoSi2/Si(1 1 1), a system previously i nvestigated by conventional tungsten tips. Compared to tungsten tips, the m easurement stability is improved, while atomic resolution is still easy to obtain in topography scans. A threshold shift in ballistic electron emissio n spectra is found to depend on the magnitude of the tunneling current. We explain this shift in terms of an ohmic series resistance in the tunneling circuit due to poor tip contacting or too low a carrier concentration in th e tip material at low temperatures. (C) 2000 Elsevier Science B.V. All righ ts reserved.