Utilizing TiO2 amorphous precursors for polymorph selection: An in situ TEM study of phase formation and kinetics
- Colorado School of Mines, Golden, CO (United States)
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
Selective synthesis of metastable polymorphs requires a fundamental understanding of the complex energy landscapes in which these phases form. Recently, the development of in situ high temperature and controlled atmosphere transmission electron microscopy has enabled the direct observation of nucleation, growth, and phase transformations with near atomic resolution. In this work, we directly observe the crystallization behavior of amorphous TiO2 thin films grown under different pulsed laser deposition conditions and quantify the mechanisms behind metastable crystalline polymorph stabilization. Films deposited at 10 mTorr chamber oxygen pressure crystallize into nanocrystalline Anatase at 325 degrees C, whereas films deposited at 2 mTorr crystallize into significantly larger needle-like grains of Brookite and Anatase at 270 degrees C. Increasing film deposition rate by a factor of 4 results in a 10x increase in the crystalline growth front velocity as well as a decrease in crystallization temperature from 270 degrees C to 225 degrees C. Engineering the amorphous precursor state through deposition conditions therefore provides routes to microstructure control and the accessibility of higher energy metastable phases.
- Research Organization:
- Energy Frontier Research Centers (EFRC) (United States). Center for Next Generation of Materials by Design: Incorporating Metastability (CNGMD); National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Grant/Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1598127
- Alternate ID(s):
- OSTI ID: 1580635
- Report Number(s):
- NREL/JA--5F00-75989
- Journal Information:
- Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 4 Vol. 103; ISSN 0002-7820
- Publisher:
- American Ceramic SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Crystallization of TiO 2 polymorphs from RF-sputtered, amorphous thin-film precursors
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journal | February 2020 |
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