Local heating in noble metal nanocontacts under high biases at 77K

Bias-induced local heating in atom-sized metal contacts at 77K

“…On the other hand, since performances of ASCs at T 0 Ͼ 4 K are more relevant to device applications than at 4 K, elucidation of the local heating in metal ASCs at higher T 0 is an important issue from a practical viewpoint. It has been demonstrated previously that T eff of Au and Cu ASCs shows negligible increase in T eff in a bias range V ഛ 0.60 V. 9,10 The absence of the overheating in Au ASCs at 77 K, together with the existence at 4 K, 11 suggests that the contact cooling is more effective at 77 K than at 4 K, in accordance with the theoretical heat dissipation via the lattice heat conduction. 2 Furthermore, it was observed that T eff of Ag ASCs starts to increase at 0.5 V at which Au and Cu ASCs show no sign of overheating.…”

Break Voltage of the 1G0 Contact of Noble Metals and Alloys

“…The break voltage of the Au 1G 0 contact shows a wide distribution that spans from 0.1 V to 2.2 V and takes a broad maximum around 1 V. The average break voltage is V b,Au = 0.93 ± 0.62 V. Smit et al [6] reported similar broad distribution for the break voltage of Au single-atom chains at 4 K and showed that the average break voltage for the 0.5-nm atomic chain is 1.2 V. The effective temperature T * of their atomic chains at [6,18]. Thus, the observed weak temperature dependence of V b,Au is consistent with the thermal activation model of the contact lifetime described by eq.…”

“…On the other hand, the room-temperature experiment has an advantage that the results should be free from any ambiguities about the contact temperature T * . Usually, T * is higher than the ambient temperature due to the local contact heating, and this has been a subject of extensive theoretical [3,[14][15][16][17] and experimental studies [5,[18][19][20]. Results of previous work suggest that the contact overheating at 1 V is significant at 4 K [19] but becomes negligible at 300 K [5,20].…”

“…From the measurement of the conductance two-level fluctuations at 77 K, Tsutsui et al [18] estimated α and obtained nearly the same α ∼ 0.1 eV/V for Au, Ag, and Cu. Thus, the observed difference in the break voltage of the Au and Cu 1G 0 contacts is likely to come form the difference in W 0 or W 0 − βF .…”

“…Although this and previous experiments indicate lower stability of the Ag 1G 0 contact compared to that of Cu, there seems to exist no specific properties, electronic and/or mechanical, that clearly distinguish Ag and Cu 1G 0 contacts and account for their different stability. Possible sources might be a local overheating of Ag 1G 0 contacts [18] and/or lower W 0 or W 0 − βF in Eq. (1).…”