Temperature at the nanoscale: thermal transport and abrupt interfaces

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Non-technical abstract Modern electronic devices contain millions of transistors generating waste heat. Removing this heat has become an increasing challenge. This is particularly important as the trend for both more and smaller transistors on a chip continues. The Principal Investigator has developed a new thermometry technique that allows the temperature of these nanoscale devices to be measured. Fahrenheit's original mercury-in-glass thermometer inferred temperature from the density changes of mercury. This technique does essentially the same thing at the nanoscale. It infers temperature changes from the density of the materials on the chip. The research team will use this new technique to study how heat flows in wires and at interfaces. The students involved in this project will receive training in state-of-the-art nanofabrication and microcopy techniques. Technical abstract In this project a new thermometry technique will be applied to the study of heat transport at very small length scales, which is both poorly understood and extremely relevant to modern electronics. The technique, plasmon energy expansion thermometry (PEET), involves measuring a material's density very accurately, and then inferring the corresponding temperature using knowledge of the material's thermal expansion. This approach is based on the same principle as Fahrenheit's original mercury-in-glass thermometer, which also infers temperature from density changes. The key advance is that here the density can be mapped with nanoscale spatial resolution, which allows the technique to produce temperature maps with unprecedented resolution. The density is determined by measuring the material's bulk plasmon energy using electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). As part of their training, students will fabricate simple microelectronic devices. Then, using the electron microscope, they will map the temperatures that result from electrically activating the devices. By imaging the thermal gradients that result from the electrical currents, it will be possible to directly connect atomic-scale structures and interfaces to the effect they have on heat generation and transport.