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Solid-Phase Epitaxial Growth of an Alumina Layer Having a Stacking-Mismatched Domain Structure of the Intermediate γ-Phase.
- Source :
-
ACS applied materials & interfaces [ACS Appl Mater Interfaces] 2018 Dec 05; Vol. 10 (48), pp. 41487-41496. Date of Electronic Publication: 2018 Nov 19. - Publication Year :
- 2018
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Abstract
- Solid-phase epitaxy (SPE), a solid-state phase transition of materials from an amorphous to a crystalline phase, is a convenient crystal growing technique. In particular, SPE can be used to grow α-Al <subscript>2</subscript> O <subscript>3</subscript> epitaxially with a novel structure that provides an effective substrate for improved performance of light-emitting diodes (LEDs). However, the inevitable two-step phase transformation through the γ-Al <subscript>2</subscript> O <subscript>3</subscript> phase hinders the expected improved crystallinity of α-Al <subscript>2</subscript> O <subscript>3</subscript> , and thereby further enhancement of LED performance. Herein, we provide a fundamental understanding of the SPE growth mechanism from amorphous to metastable γ-Al <subscript>2</subscript> O <subscript>3</subscript> using transmission electron microscopy (TEM) and density functional theory (DFT) calculations. The nanobeam precession electron diffraction technique enabled clear visualization of the double-positioning domain distribution in the SPE γ-Al <subscript>2</subscript> O <subscript>3</subscript> film and emphasized the need for careful selection of the viewing directions for any investigation of double-positioning domains. Void and stacking fault defects further investigated by high-resolution scanning TEM (STEM) analyses revealed how double-positioning domains and other SPE growth behaviors directly influence the crystallinity of SPE films. Additionally, DFT calculations revealed the origins of SPE growth behavior. The double-positioning γ-Al <subscript>2</subscript> O <subscript>3</subscript> domains randomly nucleate from the α-Al <subscript>2</subscript> O <subscript>3</subscript> substrate regardless of the α-Al <subscript>2</subscript> O <subscript>3</subscript> termination layer, but the large energy requirement for reversal of the γ-Al <subscript>2</subscript> O <subscript>3</subscript> stacking sequence prevents it from switching the domain type during the crystal growth. We expect that this study will be useful to improve the crystallinity of SPE γ- and α-Al <subscript>2</subscript> O <subscript>3</subscript> films.
Details
- Language :
- English
- ISSN :
- 1944-8252
- Volume :
- 10
- Issue :
- 48
- Database :
- MEDLINE
- Journal :
- ACS applied materials & interfaces
- Publication Type :
- Academic Journal
- Accession number :
- 30398854
- Full Text :
- https://doi.org/10.1021/acsami.8b13818