gallium (4 wt%) doped ZnO (gZO) thin films were deposited on hydrothermally grown ZnO buffered and non-buffered MgAl2O4 (1 1 1) substrates by RF magnetron sputtering technique at a growth temperature of 250 °C. The epitaxial ZnO buffer layer was deposited on the MgAl 2O4 (1 1 1) substrate by a hydrothermal technique using aqueous solutions of zinc nitrate hexahydrate, ammonium nitrate and ammonium hydroxide at 90 °C. The effect of the ZnO buffer layer on the crystallinity, epitaxial nature, surface morphology, optical and electrical properties of the gZO thin films is investigated. X-ray diffraction and transmission electron microscopy showed that the hydrothermally grown ZnO buffer layer and gZO thin film grown on the hydrothermally grown ZnO buffered substrate were grown epitaxially with an orientation relationship of (0001)[ 112̄0]gZO||(111)[112̄]MgAl2O4. However, the gZO thin films grown on the non-buffered substrate are polycrystalline in nature with a hexagonal wurtzite phase. The room temperature photoluminescence spectra of the gZO epitaxial thin films grown on the buffered substrate revealed a sharp near band edge emission peak and a lower broad deep-level emission peak compared to the polycrystalline gZO thin film grown on a non-buffered substrate. The electrical resistivity of the gZO thin films is found to be proved from 4.69×10-3 to 2.27×10-3 Ω cm by introducing the hydrothermally grown ZnO buffer layer between the gZO thin film and MgAl2O4 (1 1 1) substrate.
Bibliographical noteFunding Information:
This study was funded by the Korea Institute of Industrial Technology (KITECH) and partially by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2010-0007691 ) and a grant from the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy (10037233). Dr. A.V. Moholkar is grateful to the Department of Science and Technology (DST), New Delhi for awarding the BOYSCAST Fellowship (File No. SR/BY/P-02/2008).
- A1. X-ray diffraction
- A2. Hydrothermal crystal growth
- A2. Single crystal growth
- B1. Oxide
- B2. Semiconducting IIV materials