Spectroscopic thermometer for nanomaterials

ScienceDaily | 3/13/2018 | Staff
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This discovery, published in Physical Review Letters, promises to improve the understanding of useful yet unusual physical and chemical behaviors that arise in materials and structures at the nanoscale. The ability to take nanoscale temperatures could help advance microelectronic devices, semiconducting materials and other technologies, whose development depends on mapping the atomic-scale vibrations due to heat.

The study used a technique called electron energy gain spectroscopy in a newly purchased, specialized instrument that produces images with both high spatial resolution and great spectral detail. The 13-foot-tall instrument, made by Nion Co., is named HERMES, short for High Energy Resolution Monochromated Electron energy-loss spectroscopy-Scanning transmission electron microscope.

Atoms - Temperature - Atoms - Scientists - HERMES

Atoms are always shaking. The higher the temperature, the more the atoms shake. Here, the scientists used the new HERMES instrument to measure the temperature of semiconducting hexagonal boron nitride by directly observing the atomic vibrations that correspond to heat in the material. The team included partners from Nion (developer of HERMES) and Protochips (developer of a heating chip used for the experiment).

"What is most important about this 'thermometer' that we have developed is that temperature calibration is not needed," said physicist Juan Carlos Idrobo of the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility at ORNL.

Thermometers - Calibration - Temperature - Graduation - Marks

Other thermometers require prior calibration. To make temperature graduation marks on a mercury thermometer, for example, the manufacturer needs to know how much mercury expands as the temperature rises.

"ORNL's HERMES instead gives a direct measurement of temperature at the nanoscale," said Andrew Lupini of ORNL's Materials Science and Technology Division. The experimenter needs only to know the energy and intensity of an atomic vibration in a material -- both of which are measured during the experiment.

Features - Peaks - Ratio - Energy - Gain

These two features are depicted as peaks, which are used to calculate a ratio between energy gain and energy loss. "From...
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