A Simple and Effective Route to Annihilate Defects in Nanocrystalline SnO2 Thin Films Prepared by Pulsed Laser Depositio
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A Simple and Effective Route to Annihilate Defects in Nanocrystalline SnO2 Thin Films Prepared by Pulsed Laser Deposition Z. W. Chen1,2, C. M. L. Wu1, C. H. Shek1, J. K. L. Lai1, Z. Jiao2, and M. H. Wu2 1 Department of Physics & Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong, China, People's Republic of 2 Institute of Nanochemistry and Nanobiology, School of Environmental and Chemical Engineering, Shanghai University, Shanghai, 200444, China, People's Republic of ABSTRACT The microstructural defects of nanocrystalline SnO2 thin films prepared by pulsed laser deposition
have
been
investigated
using
transmission
electron
microscopy,
high-resolution transmission electron microscopy and Raman spectroscopy. Defects inside nanocrystalline SnO2 thin films could be significantly reduced by annealing the SnO2 thin films at 300 °C for 2 h. High-resolution transmission electron microscopy showed that stacking faults and twins were annihilated upon annealing. In particular, the edges of the SnO2 nanoparticles demonstrated perfect lattices free of defects after annealing. Raman spectra also confirmed that annealing the specimen was almost defect-free. By using thermal annealing, defect-free nanocrystalline SnO2 thin films can be prepared in a simple and practical way, which holds promise for applications as transparent electrodes and solid-state gas sensors.
Keywords: SnO2 thin film; Defect; Pulsed laser deposition; Annealing
1. Introduction In recent years, nanocrystalline SnO2 has been reported to have some different characteristics from the bulk crystals, and much attention has been
focused on the synthesis of SnO2 nanowires,1 nanotubes,1 nanorods,2,3 nanobelts,4-6 and exploration of their novel properties. Nanocrystalline SnO2 thin films have also aroused much attention since the higher-quality synthesis of SnO2 thin films was achieved. This achievement is mainly due to the recognition of the bulk-quantity growth mechanism of SnO2 thin films. The success in higher-quality synthesis of SnO2 thin films has meant that research is not limited to theoretical area, but can be extended to the experimental area. A variety of methods, such as sol-gel,7,8 chemical vapor deposition,9,10
magnetron
sputtering,11
sonochemical,12
and
thermal
evaporation,13 have been employed to prepare SnO2 thin films or nanoparticles. To date, numerous experimental results on SnO2 thin films have been reported,14-17 including those from X-ray diffraction, transmission electron microscopy (TEM), electron transport, Raman spectroscopy. These results have helped to speed up the study of its potential applications, since SnO2 thin film is one of the promising materials for future transparent nanoelectrodes and solid-state gas nanosensors. However, the as-grown SnO2 thin films typically possess a high density of defects, which would degrade their properties.18,19 Therefore, synthesis of defect-free SnO2 thin films is of great interest. The diversity of thin films grown using pulsed laser
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