Titanium Contacts to MoS2 with Interfacial Oxide: Interface Chemistry and Thermal Transport

TL;DR

This study investigates how thin oxide layers at metal/MoS2 interfaces affect interface chemistry and thermal transport, showing that such layers can reduce electrical resistance without impairing heat flow in 2D devices.

Contribution

It provides detailed analysis of interface chemistry and thermal conductance in Ti/MoS2 contacts, revealing that thin TiOx layers do not hinder heat transfer despite chemical differences.

Findings

Ti reacts strongly with MoS2, forming interface reactions.

Thin TiOx layers do not alter thermal boundary conductance significantly.

Oxide layers can reduce electrical contact resistance without affecting heat flow.

Abstract

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.