Formation and Conductance of Cd and Ti Single-Atom Contacts at Room Temperature

Break junctions of some HCP metals are known to yield single -atom contacts (SACs) frequently at 4 K but rarely at room temperature (RT). In this work, we show that SACs of Cd and Ti can be produced at RT not by opening their junctions but by closing them. For both Cd and Ti, the conductance histogram measured at junction closing reveals a clear SAC peak whereas the SAC peak appears marginal in the histogram obtained at junction opening. Because SACs are formed through necking deformations in the junction opening, while not in the junction closing, our observations suggest that the rare SAC formation reported for some HCP break junctions at RT would be due to necking deformations. The observed histograms also determine the hitherto unknown SAC conductance of Cd and Ti as 0.7G(0) and 0.8G(0), respectively.