"Transport in Nanoscale Metal-Semiconductor Contacts"

L. Hao and P. A. Bennett, Arizona State University

Current-voltage measurements and model calculations are presented for nanoscale metal-silicon contacts in UHV. Metal contacts are epitaxial CoSi₂ islands or nanowires on silicon, which form atomically perfect structures. Alternatively, the tungsten STM tip itself may be used to form a “point contact”. For the island structures, the conductance at zero bias is found to be G₀ ~ (10¹⁰ ohm)^-1, independent of island size in the range 10 – 100 nm. For point contacts, G₀ varies systematically with sub-monolayer coverage of Co, in the range from (10⁶ – 10⁸ ohm)^-1. This behavior is explained with a transport model that is dominated by surface recombination and generation currents. The same mechanism is expected to play a dominant role in surface transport measurements, in general.