We examine the electrical/thermal contact between Pt-coated pyramidal Si probes and a 100 nm thick Au film using conductive atomic force microscopy (C-AFM). For all tips, the series resistance after initial contact was not a strong function of applied force over the observed range. Mechanical contact in this range of forces without an applied voltage between tip and Au film did not produce any observable tip deformation or wear as determined by SEM examination. Changes in tip morphology after applying voltage between the tips and Au film can be attributed to two different mechanisms. At relatively high applied voltages, evidence for tip melting was observed. Increases in tip/film contact resistance as a function of applied power allows an estimate of the thermal resistance experienced by heat generated at the tip and flowing to thermal ground. In addition to tip damage caused by melting, evidence was also seen of current induced welding of the Pt coating to the Au film in the absence of any significant heating at low applied voltages (10 mV). To explain the observation in the absence of sufficient temperature rise to induce melting, we characterize electromigration in the C-AFM and examine the maximum permissible current density of tips with different sizes as a function of stress.

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