Structure, Electrical, and Mechanical Properties of Silver Nanocontacts

Abstract

Silver (Ag) nanocontacts (NCs) were produced by the retraction of a Ag nanotip from its contact with a Ag plate at room temperature inside a transmission electron microscope. The nanotip–plate distance was increased with a constant speed to thin the NCs, and the atomic configuration, applied force and stress, conductance, and current density of the NCs were investigated. The stress during thinning was analyzed as a function of strain, and the Young's modulus of the NCs was estimated. It was found that the Young's modulus, i.e., the elastic property, of the NCs changes when the minimum cross-sectional width of the NCs decreases to less than ∼1 nm. The critical shear stress of the NCs increased to 0.2 GPa when the width decreased to less than ∼1.5 nm, suggesting that the deformation mechanism of the NCs changed from dislocation-mediated slips to homogeneous slips owing to thinning. The nanotip–plate distance was also controlled using a conductance feedback system. Ag NCs exhibiting conductances of 1–3G0 (where G0 = 2e2/h; where e is the charge of an electron and h is Planck's constant) were observed continuously. When feedback conductance was assigned to be 1G0, zero-length contacts of width with one, two, and three atoms, were observed under a force of 4–5 nN with a count ratio of 27, 60, and 13%, respectively. It was demonstrated that several types of contacts exhibit the same conductance at the quantized levels.