Figure 4. Characterization of power dissipation in a quasi-ballistic single-atom contact.

(a) The measurement set up used for detection of local electrical heating in a Au single atom contact. Bias voltage V_Au was swept in a range from −0.1 V to 0.1 V and the resistance R_t of the thermometer was simultaneously recorded. (b) Formation of a Au single-atom wire using the self-breaking technique at T₀ = 80 K under V_Au = 0.05 V. The contact conductance G_Au ( = 1/R_Au) exhibits a flat plateau at about 1 G₀ during mechanical stretching signifying junction thinning to a single-atom size. Inset is the average current-voltage (<I> – V_Au) characteristics measured for a Au single-atom contact. (c) The local temperature change ΔT_t at the thermometer during the voltage sweep on the single-atom junction estimated from the average Pt coil resistance <R_t>. (d) Plots of ΔT_t with respect to P_Au = V_Au²/ R_Au. Red (blue) dots correspond to ΔT_t at V_Au < 0 V (V_Au > 0 V) in (b). (e) The noise spectrum of Au single atom wire. Dashed lines are a guide to the eyes. Arrows point to the lowest peak that represents an onset of local ionic heating in the atomic bridge. (f) Hot electron heating mechanism. A hot spot is generated at the different side of the junction depending on the bias polarity. Scale bars denote 1 μm.