Huang, ShiminGu, ShulinZhu, ShunmingGu, RanTang, KunYe, JiandongZhang, RongShi, YiZheng, Youdou2015-09-242015-09-241071-1023http://hdl.handle.net/1885/15686The properties of ZnO buffer layers grown via metal-organic chemical vapor deposition (MOCVD) on sapphire substrates after various thermal pretreatments are systematically investigated. High-temperature pretreatments lead to significant modifications of the sapphire surface, which result in enhanced growth nucleation and a consequent improvement of the surface morphology and quality of the ZnO layers. The evolution of the surface morphology as seen by atomic force microscopy indicates an obvious growth mode transition from three-dimensional to quasi-two-dimensional as the pretreatment temperature increases. A minimum surface roughness is obtained when the pretreatment temperature reaches 1150 °C, implying that a high-temperature pretreatment at 1150 °C or above may lead to a conversion of the surface polarity from O-face to Zn-face, similar to processes in GaN material growth via MOCVD. By analyzing the evolution of the film properties as a function of pretreatment temperature, the optimal condition has been determined to be at 1150 °C. This study indicates that a high-temperature pretreatment is crucial to grow high-quality ZnO on sapphire substrates by MOCVD.This research was supported by the State Key Program for Basic Research of China under Grant No. 2011CB302003, National Natural Science Foundation of China (Nos. 61025020, 60990312, and 61274058), Basic Research Program of Jiangsu Province (BK2011437), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.6 pageshttp://www.sherpa.ac.uk/romeo/issn/1071-1023..."Publishers version/PDF may be used on author's personal website, institutional website or institutional repository" from SHERPA/RoMEO site (as at 24/09/15). Copyright 2013 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in (Huang, Shimin, et al. "Thermal pretreatment of sapphire substrates prior to ZnO buffer layer growth." Journal of Vacuum Science & Technology B 31.5 (2013): 051203.) and may be found at https://doi.org/10.1116/1.4817825Keywords: Growth-mode transition; Minimum surface roughness; Optimal conditions; Pretreatment temperature; Sapphire substrates; Surface polarities; Thermal pre-treatment; Thermal pretreatments; Atomic force microscopy; Buffer layers; Metallorganic chemical vapor de2013-08-1210.1116/1.48178252016-02-24