Spatial Mapping of Thermal Boundary Conductance at Metal-Molybdenum Diselenide Interfaces

Improving the thermal transport across interfaces is a necessary consideration for micro- and nanoelectronic devices and necessitates accurate measurement of the thermal boundary conductance (TBC) and understanding of transport mechanisms. Two-dimensional transition-metal dichalcogenides (TMDs) have been studied extensively for their electrical properties, including the metal-TMD electrical contact resistance, but the thermal properties of these interfaces are significantly less explored irrespective of their high importance in their electronic devices. We isolate individual islands of MoSe₂ grown by chemical vapor deposition using photolithography and correlate the 2D variation of TBC with optical microscope images of the MoSe₂ islands. We measure the 2D spatial variation of the TBC at metal-MoSe₂-SiO₂ interfaces using a modified time-domain thermoreflectance (TDTR) technique, which requires much less time than full TDTR scans. The thermoreflectance signal at a single probe delay time is compared with a correlation curve, which enables us to estimate the change in the signal with respect to the TBC at the metal-MoSe₂-SiO₂ interface as opposed to recording the decay of the thermoreflectance signal over delay times of several nanoseconds. The results show a higher TBC across the Ti-MoSe₂-SiO₂ interface compared to Al-MoSe₂-SiO₂. An image-clustering method is developed to differentiate the TBC for different numbers of MoSe₂ layers, which reveals that the TBC in single-layer regions is higher than that in the bilayer. We perform traditional TDTR measurements over a range of delay times and verify that TBC is higher at the Ti-MoSe₂-SiO₂ interface compared to Al-MoSe₂-SiO₂, highlighting the importance of the choice of metal for heat dissipation at electrical contacts in TMD devices.