Chemical Reactions Impede Thermal Transport Across Metal/β-Ga<sub>2</sub>O<sub>3</sub> Interfaces.
basic_science · Level V
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- Record sourced from PubMed, PMID 31747285.
- Also identified by DOI 10.1021/acs.nanolett.9b03017.
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Abstract
The impact of chemical reactions on the thermal boundary conductance (TBC) of Au/metal contact/β-Ga<sub>2</sub>O<sub>3</sub> layered samples as a function of contact thickness is investigated using high-throughput thermoreflectance measurements. A maximum in TBC of 530 ± 40 (260 ± 25) MW/m<sup>2</sup> K is discovered for a Cr (Ti) contact at a thickness of 2.5 (5) nm. There is no local maximum for a Ni contact, for which the TBC saturates at 410 ± 35 MW/m<sup>2</sup> K for thicknesses greater than 3 nm. Relative to the Au/β-Ga<sub>2</sub>O<sub>3</sub> interface, which has a TBC of 45 ± 7 MW/m<sup>2</sup> K, these nanoscale contacts enhance TBC by factors of 6 to 12. The TBC maximum only exists for metals capable of forming oxides that are enthalpically favorable compared to β-Ga<sub>2</sub>O<sub>3</sub>. The formation of Cr<sub>2</sub>O<sub>3</sub>, via oxygen removal from the β-Ga<sub>2</sub>O<sub>3</sub> substrate, is confirmed by TEM analysis. The reaction-formed oxide layer reduces the potential TBC and leads to the maximum, which is followed by a plateau at a lower value, as its thickness saturates due to passivation. Many advanced materials are prone to similar chemical reactions, impacting contact engineering and thermal management for a variety of applications.