Nanoscale electron thermometry with a scanning tunneling microscope

The design of efficient electronic devices calls for a thorough understanding of dissipation, which originates at the microscopic scale when charge carrier interact with phonons and disorder and generate heat. While modern thermometry techniques have achieved remarkable temperature (mK) and spatial resolution (∼ 10 nm), they tend to spatially map the local lattice temperature of an operating device rather than the temperature of the electrons themselves. In materials with exceptionally weak electron-phonon coupling, such as graphene, the electronic temperature is effectively decoupled from the lattice temperature, and unconventional heat flows are expected to appear. Experimentally detecting such heating patterns will benefit from a high-resolution scanned probe sensitive to the local electronic temperature. In this talk, I will describe a way to use scanning tunneling microscopy to extract the local electron temperature induced by DC current flows with sub-nanometer spatial resolution. I apply this technique to study the Joule heating of back gated monolayer graphene devices, and describe how to account for tip-induced gating effects that modify that local Seebeck coefficient of the tip-sample tunnel junction.