ZnO Heteroepitaxy on Sapphire Using a Novel Buffer Layer of Titanium Oxide: Crystallographic Behavior

Satoshi Yamauchi, Yoh Imai

Department of Biomolecular Functional Engineering, Ibaraki University, Hitachi, Japan.
Department of Electric and Electronic Engineering, Ibaraki University, Hitachi, Japan.

DOI: 10.4236/csta.2013.22006                

Abstract

A novel buffer layer consists of titanium oxide grown on a-sapphire by low-pressure chemical vapor deposition using titanum-tetra-iso-propoxide and oxygen gas was used for ZnO epitaxial growth at temperature as low as 340℃ by plasma-assisted epitaxy using radio-frequency oxygen-gas plasma. XRD and RHEED indicated (0001)Ti₂O₃ layer in corundum crystal system was epitaxially grown on the substrate in an in-plane relationship of [1-100]Ti₂O₃// [0001]Al₂O₃ by uniaxial phase-lock system. Growth behavior of ZnO layer was significantly dependent on the Ti₂O₃ buffer-layer thickness, for example, dense columnar ZnO-grains were grown on the buffer layer thinner than 10 nm but the hexagonal pyramid-like grains were formed on the thin buffer layers below 2 nm. RHEED observations showed ZnO layer including the pyramid-like grains was epitaxially grown with single-domain on the thin buffer layer of 0.8 nm in the in-plane relationship of [1-100]ZnO//[1-100]Ti₂O₃//[0001]Al₂O₃, whereas the multi-domain was included in ZnO layer on the buffer layer above 10 nm.

Keywords

ZnO; Ti₂O₃; Plasma-Assisted Epitaxy; Hexagonal Pyramid Grain

Conflicts of Interest

The authors declare no conflicts of interest.

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