Chemical vapor deposition of zinc oxide thin films on Y2O3/Si substrates

Highly-oriented ZnO films were deposited on Y2O3/Si(111) and Y2O3/Si(100) substrates by atmospheric pressure metal-organic chemical vapor deposition (MOCVD) using zinc acetylacetonate (Zn(C5H7O2)(2)) and oxygen as sources. The substrate temperature and O-2 gas temperature were all kept at 500 degreesC. Y2O3, thermodynamically more stable than SiO2 and epitaxially formed on Si, is used as buffer layer. Epitaxial Y2O3 of 200 nm thickness were first grown by pulsed laser deposition on Si(111) and Si(100) substrates at 800 degreesC for 30 min. X-ray diffraction patterns of the samples only show sharp diffraction peaks of Y2O3{222} and ZnO{0002}. The photoluminescence spectra of ZnO show strong peaks of near the band edge and very weak peaks of deep-level emission at 7 K and room temperature. Cross-sectional transmission electron microscopy shows that the highly-oriented ZnO films has columnar structure with a grain size distribution of 600-850 Angstrom. Most of ZnO grains exhibit orientation relationship with Y2O3 as {0002}(ZnO)//{222}(Y2O3), <0110>(ZnO)//(112)(Y2O3), and <1120>(ZnO)//<110>(Y2O3). (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.