Single electron tunneling of nanoscale TiSi ₂ islands on Si

Nanoscale TiSi ₂ islands are formed by electron beam deposition of a few monolayers of titanium on an atomically clean silicon surface followed by in situ annealing at high temperatures (800-1000°C). The lateral diameter of typical islands are ∼5 nm, and they form a nanoscale metal-semiconductor interface. Direct probing of the electrical characteristics of these islands on both p- and n-type Si substrates was performed using ultrahigh vacuum scanning tunneling microscopy and scanning tunneling spectroscopy. With the vacuum between the tip and the island as a second tunnel junction, we thus form a double-junction system for observation of single electron tunneling (SET) effects. Moreover, the small dimensions of the system allow room temperature observation. The results showed features in the I-V spectra attributed to single electron tunneling. Features were more evident when the island-Si junction was in reverse bias. For substrates with a thin epitaxial layer of intrinsic Si, the tunneling related features were enhanced for both doping types. The experimental results are compared with the standard theory and numerical values from the fitting are in agreement with the experimental structures. The results indicate that the nanoscale Schottky barrier of the island-substrate interface can be employed as a tunnel barrier in SET structures.