Monday, February 13, 2017
Modern microelectronic devices such as the ubiquitous transistor produce temperature gradients of kelvins per nanometer. Optical techniques that are sensitive to temperature, such as pyrometry and Raman spectroscopy, are diffraction limited and cannot resolve these nanoscale temperature gradients. Contact thermometers, often made of atomically sharp thermocouples, require a thermal connection that can alter a small system’s temperature. By building on the basic physics of a glass-bulb thermometer, we have developed a new way to measure temperature with nanometer-scale spatial resolution. We use a focused electron probe (less than a nanometer in width) and electron energy loss spectroscopy to measure quantized plasmon energies, which provides parts-per-thousand sensitivity to changes in density. By translating density to temperature using a known thermal expansion coefficient, we can measure temperature changes with a statistical precision of 3 kelvin/√Hz. With a sufficiently sharp plasmon resonance, common in many metals and semiconductors, any material being probed using this non-contact technique can act as its own thermometer. This thermometry technique opens up new ways to study heat transport, the Nernst and Ettingshausen effects in 2D materials, and nanoscale cooling using thermoelectrics.
Matthew Mecklenburg Bio:
Dr. Matthew Mecklenburg graduated from UCLA with a Ph. D. in physics in the Fall of 2011. His thesis work involved understanding electron and photon interactions with graphene. After graduation, he worked as a staff scientist and principal investigator at The Aerospace Corporation, the US Air Force’s federally funded research and development center for space technology. There he developed new in situ transmission electron microscopy techniques to study physical phenomena. He currently works at USC’s Center for Electron Microscopy and Microanalysis (CEMMA) as a staff scientist and principal investigator studying nanoscale thermal and electrical transport.