Method to reduce the formation of crystallites in ZnO nanorod thin-films grown via ultra-fast microwave heating

• Published in: Thin solid films Vol. 662; pp. 116 - 122
• Main Authors: Gray, R.J., Jaafar, Ayoub H., Verrelli, E., Kemp, N.T.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.09.2018
• Subjects: Crystallites; Hydrothermal growth; Memristors; Nanorods; Nucleation; Semiconductor; Thin-films; Zinc oxide; Hydrothermal growth; Crystallites; Semiconductor; Nucleation; Memristors; Zinc oxide; Thin-films; Nanorods
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2018.07.034

This paper discusses the nucleation and growth mechanisms of ZnO nanorod thin-films and larger sized crystallites that form within the solution and on surfaces during an ultra-fast microwave heating growth process. In particular, the work focusses on the elimination of crystallites as this is necessary to improve thin-film uniformity and to prevent electrical short circuits between electrodes in device applications. High microwave power during the early stages of ZnO deposition was found to be a key factor in the formation of unwanted crystallites on substrate surfaces. Once formed, the crystallites, grow at a much faster rate than the nanorods and quickly dominate the thin-film structure. A new two-step microwave heating method was developed that eliminates the onset of crystallite formation, allowing the deposition of large-area nanorod thin-films that are free from crystallites. A dissolution-recrystallization mechanism is proposed to explain why this procedure is successful and we demonstrate the importance of the work in the fabrication of low-cost memristor devices. •Presence of crystallites affects memristor device performance.•New method of reducing crystallites in microwave-assisted ZnO nanorod thin-films.•Heating rate is a significant contributor to the formation of large crystallites.•Control of the initial growth is essential for crystallite free ZnO nanorod films.