Electrical Properties of Nanometer-Size Metal-Semiconductor Point Contacts

Abstract

Using scanning tunneling microscopy (STM) with a metal tip and a semiconductor surface, we made metal-semiconductor interfaces with a contact area of nanometer size and studied their electrical properties. I–V curves measured at the interfaces show a significant leak conductance in addition to a diode-like exponential component. The amplitude of the leak conductance depends on the properties of the semiconductor surface. For instance, in the case of the Si(l11)7×7 surface, it decreases exponentially with exposure to oxygen, and the conductance of the interface formed on semiconductor islands are lower than that formed on a flat area. Since the conductance does not depend on the dopant type of semiconductor samples, and thus, cannot be explained with a space charge layer model of surface conductivity, we speculate that the leak conductance is due to a conductivity via surface states of semiconductor samples.