Misfit reduction by a spinel layer formed during the epitaxial growth of ZnO on sapphire using a MgO buffer layer

A. Bakin, J. Kioseoglou, B. Pécz, A. El-Shaer, A. C. Mofor, J. Stoemenos, A. Waag

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The quality of the ZnO films, epitaxially grown on sapphire, can be substantially improved when a MgO buffer layer is used. The role and the structural characteristics of this buffer layer were studied by transmission electron microscopy. It was found that during the MgO deposition and the subsequent ZnO deposition Mg and Al interdiffusion occurs between the MgO buffer layer and the Al2O3 substrate forming an intermediate spinel MgAl2O4 layer at the deposition temperature of 700 °C. This layer has the following epitaxial relation with the substrate, [1 over(1, -) 0 0]sapphire//[1 over(1, -) 0]spinel, and [1 1 over(2, -) 0]sapphire//[1 1 over(2, -)]spinel, also [0 0 0 1]sapphire//[1 1 1]spinel. The misfit between the two lattices is about 2.6% considering that every second (3 0 over(3, -) 0) sapphire plane corresponds to a (2 2 0) spinel plane. Thus, the original misfit between ZnO and sapphire is progressively decreased by the spinel layer. The formation of the spinel intermediate layer during the early stage of growth was also studied during the deposition of the MgO buffer layer. The stability of the spinel layer was tested by annealing at 1000 °C.

Original languageEnglish
Pages (from-to)314-320
Number of pages7
JournalJournal of Crystal Growth
Volume308
Issue number2
DOIs
Publication statusPublished - Oct 15 2007

Fingerprint

Aluminum Oxide
Buffer layers
Epitaxial growth
Sapphire
spinel
sapphire
buffers
Substrates
spinell
Annealing
Transmission electron microscopy
transmission electron microscopy
annealing

Keywords

  • A1. Interfaces
  • A1. Transmission electron microscopy
  • A3. Molecular beam epitaxy
  • B2. Semiconducting II-VI materials

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Misfit reduction by a spinel layer formed during the epitaxial growth of ZnO on sapphire using a MgO buffer layer. / Bakin, A.; Kioseoglou, J.; Pécz, B.; El-Shaer, A.; Mofor, A. C.; Stoemenos, J.; Waag, A.

In: Journal of Crystal Growth, Vol. 308, No. 2, 15.10.2007, p. 314-320.

Research output: Contribution to journalArticle

Bakin, A. ; Kioseoglou, J. ; Pécz, B. ; El-Shaer, A. ; Mofor, A. C. ; Stoemenos, J. ; Waag, A. / Misfit reduction by a spinel layer formed during the epitaxial growth of ZnO on sapphire using a MgO buffer layer. In: Journal of Crystal Growth. 2007 ; Vol. 308, No. 2. pp. 314-320.
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AB - The quality of the ZnO films, epitaxially grown on sapphire, can be substantially improved when a MgO buffer layer is used. The role and the structural characteristics of this buffer layer were studied by transmission electron microscopy. It was found that during the MgO deposition and the subsequent ZnO deposition Mg and Al interdiffusion occurs between the MgO buffer layer and the Al2O3 substrate forming an intermediate spinel MgAl2O4 layer at the deposition temperature of 700 °C. This layer has the following epitaxial relation with the substrate, [1 over(1, -) 0 0]sapphire//[1 over(1, -) 0]spinel, and [1 1 over(2, -) 0]sapphire//[1 1 over(2, -)]spinel, also [0 0 0 1]sapphire//[1 1 1]spinel. The misfit between the two lattices is about 2.6% considering that every second (3 0 over(3, -) 0) sapphire plane corresponds to a (2 2 0) spinel plane. Thus, the original misfit between ZnO and sapphire is progressively decreased by the spinel layer. The formation of the spinel intermediate layer during the early stage of growth was also studied during the deposition of the MgO buffer layer. The stability of the spinel layer was tested by annealing at 1000 °C.

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