Utilizing TiO2 Amorphous Precursors for Polymorph Selection: An in situ TEM study of Phase Formation and Kinetics

David Ginley, John Mangum, Brian Gorman, Lauren Garten

Research output: Contribution to journalArticlepeer-review

8 Scopus Citations

Abstract

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°C, whereas films deposited at 2 mTorr crystallize into significantly larger needle-like grains of Brookite and Anatase at 270°C. Increasing film deposition rate by a factor of 4 results in a 10× increase in the crystalline growth front velocity as well as a decrease in crystallization temperature from 270°C to 225°C. Engineering the amorphous precursor state through deposition conditions therefore provides routes to microstructure control and the accessibility of higher energy metastable phases.

Original languageAmerican English
Pages (from-to)2899-2907
Number of pages9
JournalJournal of the American Ceramic Society
Volume103
Issue number4
DOIs
StatePublished - 2020

Bibliographical note

Publisher Copyright:
© 2019 American Ceramic Society

NREL Publication Number

  • NREL/JA-5F00-75989

Keywords

  • amorphous
  • crystals/crystallization
  • thin films
  • titanium dioxide

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