Scientists at Oak Ridge National Laboratory (ORNL) have discovered a way to take the temperature of materials from an area that is 100,000 times thinner than a single human hair. The discovery was made by the Department of Energy and published in Physical Review Letters.
The method that the team at ORNL have been using combines both electron energy gain and loss spectroscopy. The techniques give direct measurements of local temperature in nano-environments, as well as electron energy gain spectroscopy producing images with high spatial resolution and spectral detail. The 13-foot-tall instrument has been dubbed the High Energy Resolution Monochromated Electron energy-loss spectroscopy-Scanning transmission electron microscope, or HERMES for short.
Heat dissipation in nanoscale devices is a problem that means nanoscale temperature probes have to be developed. The new HERMES instrument measures the temperatures of semiconducting hexagonal boron nitride by observing the atomic vibrations from heat within the material.
What is most important about this ‘thermometer’ that we have developed is that temperature calibration is not needed.
Juan Carlos Idrobo, Staff Scientist - Center for Nanophase Materials Sciences
Sample materials are placed in the electron microscope, and the microscope’s electron beam goes through the sample. In electron energy loss spectroscopy, the beam loses energy as it passes through the sample, but in energy gain spectroscopy the electrons gain energy from interaction with the sample.
When HERMES is used, only the energy and intensity of an atomic vibration in a material is needed, both of which are measured during the experiment. They are shown as peaks and are then used to calculate a ratio between energy gain and energy loss to get the temperature.
We don’t need to know anything about the material beforehand to measure temperature.
Andrew Lupini, Staff Scientist - Center for Nanophase Materials Sciences
The new HERMES lets us look at very tiny energy losses and even very small amounts of energy gain by the sample.
Juan Carlos Idrobo, Staff Scientist - Center for Nanophase Materials Sciences
The ability to take nanoscale temperatures can help to advance microelectronic devices, semiconducting materials, and technologies that depend on the mapping of atomic-scale heat vibrations. The nanoscale resolution also makes it possible to characterize local temperature during phase transitions of materials. HERMES can be used across a wide range of temperatures, including electronics under ambient conditions through to vehicle catalysts that are over 300 degrees Celsius.
Source: https://www.ornl.gov/news/researchers-develop-spectroscopic-thermometer-nanomaterials
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