Bonding enhances thermal conductance across Au/Si interfaces

Our paper – Duda et al. “Influence of interfacial properties on thermal transport at gold:silicon contacts,” was recently published in Applied Physics Letters (Appl. Phys. Lett102, 081902 (2013)).  In this paper, we measured the thermal boundary conductance across Au/Si interfaces with varying degrees of roughness and “adhesion” (i.e., Au/native oxide/Si, Au/Ti/native oxide Si and Au/Ti/Si).  We find that roughness affects the low frequency phonon transmission, as measured via picosecond ultrasonics.  We also demonstrate that a Ti adhesion layer, which increases the Au/Si bonding, can lead to a factor of 3 increase in thermal boundary conductance.

Abstract

We measure the Kapitza conductances at Au:Si contacts from 100 to 296 K via time-domain thermoreflectance. Contacts are fabricated by evaporating Au films onto Si substrates. Prior to Au deposition, the Si substrates receive pretreatments in order to modify interfacial properties, i.e., bonding and structural disorder. Through the inclusion of a Ti adhesion layer and the removal of the native oxide, Kapitza conductance can be enhanced by a factor of four at 296 K. Furthermore, interfacial roughness is found to have a negligible effect, which we attribute to the already low conductances of poorly bonded Au:Si contacts.

This work was funded by NSF (CBET Award #1134311) and Sandia National Laboratories through the LDRD Program Office.

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