期刊
NATURE COMMUNICATIONS
卷 8, 期 -, 页码 -出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/ncomms15316
关键词
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资金
- U.S. DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division
- ORNL's Center for Nanophase Materials Sciences (CNMS), an Office of Science User Facility
- NASA Kentucky under NASA [NNX10AL96H]
- National Science Foundation [DMR 1504702, DMR 1455154, CMMI 1534534]
- Air Force Office of Scientific Research [AFOSR-FA9550-16-1-0180]
- Direct For Mathematical & Physical Scien [1455154] Funding Source: National Science Foundation
- Division Of Materials Research [1455154] Funding Source: National Science Foundation
- Div Of Civil, Mechanical, & Manufact Inn
- Directorate For Engineering [1534534] Funding Source: National Science Foundation
High-temperature phases of hafnium dioxide have exceptionally high dielectric constants and large bandgaps, but quenching them to room temperature remains a challenge. Scaling the bulk form to nanocrystals, while successful in stabilizing the tetragonal phase of isomorphous ZrO2, has produced nanorods with a twinned version of the room temperature monoclinic phase in HfO2. Here we use in situ heating in a scanning transmission electron microscope to observe the transformation of an HfO2 nanorod from monoclinic to tetragonal, with a transformation temperature suppressed by over 1000 degrees C from bulk. When the nanorod is annealed, we observe with atomic-scale resolution the transformation from twinned-monoclinic to tetragonal, starting at a twin boundary and propagating via coherent transformation dislocation; the nanorod is reduced to hafnium on cooling. Unlike the bulk displacive transition, nanoscale size-confinement enables us to manipulate the transformation mechanism, and we observe discrete nucleation events and sigmoidal nucleation and growth kinetics.
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