Structure and Tensile Force of Nanometer- and Atomic-Sized Gold Contacts during Conductance Feedback Control

Nanometer- and atomic-sized gold (Au) contacts were produced by the retraction of a Au nanotip from contact with a Au plate at room temperature inside a transmission electron microscope. The nanotip-plate distance was controlled using a conductance feedback system. Au contacts showing certain conductance were observed continuously by in situ lattice imaging with simultaneous force measurements. When feedback conductance was selected to be 1G(0) (where G(0) = 2e(2)/h, where e is the charge of an electron and h Planck's constant), three types of Au contacts, i.e., zero-length contacts of one-, two-, and three-atom width, were observed under a stress of similar to 8 GPa with a counting ratio of 54, 36, and 10%, respectively. Similarly, for feedback conductance of 2G(0), 3G(0), 4G(0), and 5G(0), Au contacts of one- to five-atom width were observed, Thus, it was demonstrated that a certain conductance corresponding to a quantized level is caused by several types of contacts. (C) 2009 The Japan Society of Applied Physics