Nanoscale Mapping of Thermal Gradients in MoS₂ from Plasmon Energy Shifts

Using a new nanoscale thermometry technique, we observe in plane temperature gradients across suspended, few layer thick, MoS₂ sheets. The temperature gradients are measured via in situ experiments in a transmission electron microscope. A map of temperatures is built up by acquiring an electron energy loss spectrum at an array of points across the MoS₂. Each spectrum is then used to precisely measure the energy of the MoS₂ bulk plasmon, whose energy is sensitive to changes in temperature due to electron density changes via thermal expansion. By Joule heating two heaters on either side of the suspended sheet we are able to induce temperature gradients in either direction. By calibrating each of the heaters output power we can then infer the suspended MoS₂’s thermal conductivity.