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Chemical Bonding, Structure, and Morphology of Mg/∝-Al2O3 and MGO / ∝-Al2O3 Interfaces

Published online by Cambridge University Press:  15 February 2011

Yan Yu  and
R.J. Lad
Yan Yu
Affiliation:
Laboratory for Surface Science & Technology, 5764 Sawyer Research Center, University of Maine, Orono, ME 04469
R.J. Lad
Affiliation:
Laboratory for Surface Science & Technology, 5764 Sawyer Research Center, University of Maine, Orono, ME 04469
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Abstract

Ultra-thin films of Mg and MgO were grown on ∝-Al2O3 (1012) surfaces (r-cut sapphire) and studied using reflection high energy electron diffraction (RHEED) and x-ray photoelectron spectroscopy (XPS). When Mg is deposited at 30°C in ultra-high vacuum (UHV), the first monolayer of Mg atoms chemically bonds to the oxygen anions of the sapphire surface. At Mg coverages above a monolayer, a polycrystalline metallic Mg overlayer is formed. Annealing above 250°C in UHV causes the metallic Mg to desorb from the surface. However, annealing above 250°C in 10−6 torr O2 produces a polycrystalline MgO film. This MgO film recrystallizes after annealing in O2 at 900°C for 60 minutes and exhibits a crystallographic orientation of MgO (100) // ∝-Al2O3 (1012). RHEED indicates that the recrystallized MgO layer dewets the sapphire surface and forms islands. When Mg is deposited at 30°C in 10−6 torr O2, a polycrystalline MgO layer is created. This layer also becomes recrystallized and dewets the sapphire surface after extended annealing in O2 at 900°C. No evidence for a MgAl2O4 spinel phase was observed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 357: Symposium C – Structure and Properties of Interfaces in Ceramics , 1994 , 47
Copyright
Copyright © Materials Research Society 1995

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