Distribution of $1G_{0}$ Plateau Length of Au Contacts at Room Temperature

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We have measured the $1G_{0}$ ($G_{0}$ is the conductance quantum unit) plateau length $\tau$ of Au breaking contacts at room temperature and examined the plateau-length distribution $P(\tau)$ for biases 0.1–2.0 V. We observed that $P(\tau)$ exhibits a long tail and obeys the power-law distribution $P(\tau)\propto\tau^{-\gamma}$ with $\gamma\sim 1$, indicating a strong diversity in the atomic configuration of the Au single-atom contacts. The exponent $\gamma$ little varies with the bias voltage and ranges between 0.8 and 1.1. We changed the contact breaking conditions, by slowing down the breaking speed and lowering the contact current, and again observed the same power-law distribution for $P(\tau)$ with $\gamma\sim 1$, whereas the average plateau length $\langle\tau\rangle$ increases at slower breaks. We also found that the Au $1G_{0}$ contacts in air show longer $\langle\tau\rangle$ than those in ultrahigh vacuum, suggesting contact stabilization by ambient air molecules.
2007-06-15