Single-defect phonons imaged by electron microscopy

Article

关键词: INITIO MOLECULAR-DYNAMICS;    VIBRATIONAL SPECTROSCOPY;    SPATIAL-RESOLUTION;    SCATTERING;   

DOI  :  10.1038/s41586-020-03049-y

来源: SCIE

【 摘 要 】

Crystal defects affect the thermal and heat-transport properties of materials by scattering phonons and modifying phonon spectra(1-8). To appreciate how imperfections in solids influence thermal conductivity and diffusivity, it is thus essential to understand phonon-defect interactions. Sophisticated theories are available to explore such interactions, but experimental validation is limited because most phonon-detecting spectroscopic methods do not reach the high spatial resolution needed to resolve local vibrational spectra near individual defects. Here we demonstrate that space- and angle-resolved vibrational spectroscopy in a transmission electron microscope makes it possible to map the vibrational spectra of individual crystal defects. We detect a red shift of several millielectronvolts in the energy of acoustic vibration modes near a single stacking fault in cubic silicon carbide, together with substantial changes in their intensity, and find that these changes are confined to within a few nanometres of the stacking fault. These observations illustrate that the capabilities of a state-of-the-art transmission electron microscope open the door to the direct mapping of phonon propagation around defects, which is expected to provide useful guidance for engineering the thermal properties of materials.

【 授权许可】

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