In situ TEM study of κ → β and κ → γ phase transformations in Ga2O3
In situ TEM study of κ → β and κ → γ phase transformations in Ga2O3
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DOI：
10.1016/j.actamat.2019.11.019
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发表时间：
2020-01-15
期刊：
影响因子：
9.4
通讯作者：
Pecz, B.
中科院分区：
文献类型：
--
作者：
Cora, I.;Fogarassy, Zs.;Pecz, B.
采用高分辨透射电镜研究了蓝宝石表面亚稳kappa-Ga2O3层的温度驱动相变过程。退火实验高达1000摄氏度，在原位真空中或在环境空气中进行。这允许在kappa到β相变的基础上检测原子机制。在原位透射电镜观察的情况下，我们甚至可以实时记录原子重排。本文给出了原kappa晶格与新β晶格之间的相关晶体学关系。令人惊讶的是，原位退火实验表明，在820℃时，额外形成了γ - ga2o3中间相。原位退火和非原位退火实验之间的显著差异行为可以用环境（环境空气或高真空）和加热速率来解释。对γ - ga2o3（也是亚稳相）的广泛研究表明，它具有立方缺陷尖晶石结构（Fd (3) over barm）和无序空位。两个月后对亚稳态γ - ga2o3的重复观察表明，空位趋于有序，一年后空位完全有序。(C) 2019材料学报Elsevier Ltd.出版。版权所有。
The temperature-driven phase transformation of metastable kappa-Ga2O3 layers deposited on sapphire was studied by high resolution TEM. Annealing experiments up to 1000 degrees C were performed either in situ in vacuum within the TEM or ex situ in ambient air. This allowed for the detection of the atomistic mechanisms at the basis of kappa to beta phase transition. In the case of in situ TEM observations we could even record in real time the atomic rearrangement. We provide in this paper the relevant crystallographic relations between original kappa and new beta lattice.Surprisingly, the ex situ experiments demonstrated the additional formation of a gamma-Ga2O3 intermediate phase at 820 degrees C. The remarkably different behavior between in situ and ex situ annealing experiments is explained in terms of ambient (ambient air or high vacuum) and heating rate.An extensive investigation of gamma-Ga2O3, also a metastable phase, showed that it has a cubic defect spinel structure (Fd (3) over barm) with disordered vacancies. Repeated observations of the metastable gamma-Ga2O3 after two months show that the vacancies tend to order, and that the vacancies are fully ordered after one year. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.