  The deposition of a thin oxide layer at metal/semiconductor interfaces has
been previously reported as a means of reducing contact resistance in 2D
electronics. Using X-ray photoelectron spectroscopy with in-situ Ti deposition,
we fabricate Au/Ti/TiOx/MoS2 samples as well as Au/Ti/MoS2 and Au/TiOx/MoS2 for
comparison. Elemental titanium reacts strongly with MoS2 whereas no interface
reactions are observed in the two types of samples containing TiOx/MoS2
interfaces. Using time domain thermoreflectance for the measurement of thermal
boundary conductance, we find that samples contacted with Ti and a thin TiOx
layer at the interface (less than or equal to 1.5 nm) exhibit the same behavior
as samples contacted solely with pure Ti. The Au/TiOx/MoS2 samples exhibit
approximately 20% lower thermal boundary conductance, despite having the same
MoS2 interface chemistry as the samples with thin oxide at the Ti/MoS2
interface. We identify the mechanism for this phenomenon, attributing it to the
different interfaces with the top Au contact. Our work demonstrates that the
use of thin interfacial oxide layers to reduce electrical contact resistance
does not compromise heat flow in 2D electronic devices. We note that the
thicknesses of the Ti and TiOx layers must be considered for optimal thermal
transport.
