Structure of nanometer-sized palladium contacts and their mechanical and electrical properties

Structural evolution in the nanometer-sized contacts (NCs) of two palladium (Pd) tips during tensile deformation was observed in situ at room temperature by transmission electron microscopy with the simultaneous measurements of force and conductance. The constants concerning the mechanical properties of individual Pd NCs, i.e., elastic limit, Young's modulus, and strength, were analyzed on the basis of stress-strain curves on an atomic scale. It was found that, in contrast to those of coarse-grained Pd crystals, the strength and elastic limit of Pd NCs with a cross-sectional area of approximately 1 nm(2) increase to 1.0 +/- 0.2 GPa and 0.04-0.16, respectively, whereas Young's modulus decreases to 3.4 +/- 10.9 GPa. The histogram of conductances showed a maximum peak at 1.6G(0) (where G(0) = 2e(2)/h, with e being the charge of an electron and h Planck's constant) and on almost constant distribution at other conductance levels.