John Tomko’s works has recently appeared in Physical Review B.
Tomko, J.A., Giri, A., Donovan, B.F., Bubb, D.M., O’Malley, S.M., Hopkins, P.E., “Energy confinement and thermal boundary conductance effects on short-pulsed thermal ablation thresholds in thin films,” Physical Review B 96, 014108 (2017). PDF.
In this work,we demonstrated a direct correlation between thermal ablation of thin gold films and the thermal boundary conductance across the film/substrate interface. We used high energy pulsed lasers to induce the film ablation and showed a dependence on substrate. However, the ablation threshold did not trend with the substrate thermal properties, but instead the thermal boundary conductance across the film/substrate interface.
Abstract
For this paper, single-pulse ablation mechanisms of ultrafast laser pulses (25 ps) were studied for thin gold films (65 nm) on an array of substrates with varying physical properties. Using time-domain thermoreflectance, the interfacial properties of the thin-film systems are measured: in particular, the thermal boundary conductance. We find that an often used, and widely accepted relation describing threshold fluences of homogeneous bulk targets breaks down at the nanoscale. Rather than relying solely on the properties of the ablated Au film, the ablation threshold of these Au/substrate systems is found to be dependent on the measured thermal boundary conductance; we additionally find no discernible trend between the damage threshold and properties of the underlying substrate. These results are discussed in terms of diffusive thermal transport and the interfacial bond strength.
This material is based upon work supported by the Air Force Office of Scientific Research under Award No. FA9550-15-1-0079. D.M.B. and S.M.O. acknowledge Awards CMMI- 1531783 and CMMI-0922946 from the National Science Foundation.
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