Nucleation and growth of ZnO on (1 1̄ 2 0) sapphire substrates using molecular beam epitaxy

P. Fons, K. Iwata, A. Yamada, K. Matsubara, S. Niki, K. Nakahara, T. Tanabe, H. Takasu

Research output: Contribution to journalConference articlepeer-review

26 Citations (Scopus)

Abstract

It has been recently demonstrated that it is possible to eliminate 30° rotation twins in c-oriented epitaxial ZnO films by growing on the (1 1̄ 2 0) face of sapphire despite the apparent symmetry mismatch between the (6-fold) epilayer and the (2-fold) substrate. To further elucidate the details of the growth process, we have investigated the initial stages of growth of ZnO on (1 1̄ 2 0) sapphire using molecular beam epitaxy. Films of approximately 3, 5, 8, 10, 20, 100, and 600 nm thickness were investigated by in situ reflection high-energy diffraction, high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), and extended X-ray absorption (XAFS). XAFS indicates that there is no discernible change in nearest-neighbor distance with film thickness. On the other hand, HRXRD measurements indicate an ∼1% increase in the c-lattice constant with decreasing film thickness. XAFS measurements of the second nearest-neighbor structural disorder were observed to increase sharply for the thinnest films implying that distortion of bond angles is responsible for the increase in the c-axis observed by HRXRD. HRXRD reciprocal area maps of the symmetric ZnO (0 0 0 2) reflection indicate the onset of diffuse scattering from 20 nm, while AFM indicates a concurrent change in surface morphology suggesting a change in the growth process for t > ∼20 nm.

Original languageEnglish
Pages (from-to)911-916
Number of pages6
JournalJournal of Crystal Growth
Volume227-228
DOIs
Publication statusPublished - 2001 Jul
Externally publishedYes
Event11th International Conference on Molecular Beam Epitaxy - Bijing, China
Duration: 2000 Sep 112000 Sep 15

Keywords

  • A1. EXAFS
  • A1. High resolution X-ray diffraction
  • A1. Initial growth
  • A3. Molecular beam epitaxy
  • B1. Oxides
  • B1. Zinc compounds

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Inorganic Chemistry
  • Materials Chemistry

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