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Interfacial Area between Hetero‐Epitaxial γ‐Al 2 O 3 and Silicon
Author(s) -
Liao Yuanxun,
Zhou Dongyi,
Shrestha Santosh,
Huang Shujuan,
Bremner Stephen,
Conibeer Gavin
Publication year - 2017
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201700259
Subject(s) - materials science , epitaxy , crystallite , stacking , crystallography , silicon , monocrystalline silicon , thin film , lattice constant , crystallinity , condensed matter physics , grain boundary , layer (electronics) , nanotechnology , optoelectronics , composite material , optics , diffraction , metallurgy , nuclear magnetic resonance , microstructure , chemistry , physics
The interfacial region between hetero‐epitaxial γ‐Al 2 O 3 and Si (111) substrates is studied in detail. The purpose is to address many open questions regarding the growth of γ‐Al 2 O 3 grown on Si, such as the atomic stacking orders, strain relaxation modes, and observed thin‐film qualities. The cross‐sectional atomic stacking order is directly evidenced to be a cubic spinel structure, with a possible in‐plane stacking order proposed. A 1.5 nm defect‐rich transition layer is found at the interface, in which the lattice structure transitions from Si to γ‐Al 2 O 3 arrangement. The thin‐film quality, in terms of crystallinity and low film roughness, is observed to improve with increasing thickness up to ≈8 nm. For thicknesses above 8 nm, grain boundaries are observed along with the appearance of pinholes, due to the large lattice constant and thermal expansion coefficient differences between γ‐Al 2 O 3 and Si. Polycrystalline islands form in these pinholes and gradually replace the initial layer‐by‐layer growth of monocrystalline γ‐Al 2 O 3 , leading to a mainly polycrystalline material at large thicknesses. The insights gained on the hetero‐epitaxy of γ‐Al 2 O 3 on Si will be useful for future work looking to exploit this hetero‐epitaxial materials system.