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Journal of Nanomaterials
Volume 2015, Article ID 179804, 5 pages
http://dx.doi.org/10.1155/2015/179804
Research Article

The Effect of Annealing on Nanothick Indium Tin Oxide Transparent Conductive Films for Touch Sensors

1Department of Optics and Photonics and Thin Film Technology Center, National Central University, Chung-Li, Taiwan
2Graduate Institute of Energy Engineering and Thin Film Technology Center, National Central University, Chung-Li, Taiwan

Received 13 November 2014; Accepted 15 April 2015

Academic Editor: Ying-Lung Daniel Ho

Copyright © 2015 Shih-Hao Chan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This study aims to discuss the sheet resistance of ultrathin indium tin oxide (ITO) transparent conductive films during the postannealing treatment. The thickness of the ultrathin ITO films is 20 nm. They are prepared on B270 glass substrates at room temperature by a direct-current pulsed magnetron sputtering system. Ultrathin ITO films with high sheet resistance are commonly used for touch panel applications. As the annealing temperature is increased, the structure of the ultrathin ITO film changes from amorphous to polycrystalline. The crystalline of ultrathin ITO films becomes stronger with an increase of annealing temperature, which further leads to the effect of enhanced Hall mobility. A postannealing treatment in an atmosphere can enhance the optical transmittance owing to the filling of oxygen vacancies, but the sheet resistance rises sharply. However, a higher annealing temperature, above 250°C, results in a decrease in the sheet resistance of ultrathin ITO films, because more Sn ions become an effective dopant. An optimum sheet resistance of 336 Ω/sqr was obtained for ultrathin ITO films at 400°C with an average optical transmittance of 86.8% for touch sensor applications.