Contacts between simple metals and atomically clean silicon

Abstract

Workfunction measurements of atomically clean silicon (111) surfaces produced by cleavage and of evaporated simple-metal films have been carried out in a UHV system at a base pressure of about 5*10^-11 Torr. The barrier heights of the resulting intimate metal-silicon contacts have also been measured without breaking the vacuum. The barrier height values derived from I-V and photoelectric measurements are in excellent agreement. However, they are lower than the barrier height values obtained from differential capacitance measurements by about 0.1 eV depending on the metal. This discrepancy is in qualitative agreement with the Heine and Inkson theories for intimate metal-semiconductor contacts. The dependence of barrier height on metal workfunction cannot be described by a simple effect on the potential barrier of intimate metal-semiconductor contacts, over and above the effect of the metal workfunction.