Transparent conductive oxide (TCO) materials have been attracted much attention for liquid crystal displays and photovoltaic devices. Especially, ITO is known as a good transparent conductive oxide material. Recently, ZnO is also expected as TCO material because material (Zn) cost is very low in comparison to that of ITO (In). ZnO has been grown by sputtering, ion-plating methods and so on. Plasma damages of a substrate and high cost of an equipment have in the both technique. Therefore, spray pyrolysis method is effective for thin film growth.
In our previous work [1], ZnO poly films were successfully grown by spray method at 300 ~ 600 °C. The XRD indicates that (0002) orientations are observed with increasing substrate temperatures. Values of FWHM also become small with increasing substrate temperatures. Grain sizes examined by the XRD data using Scherrer's equation are in good agreement with those obtained by the SEM. Resistivities decrease with increasing doping In concentration. These indicate that In atoms act as donor impurities such as substitutional In in Zn site.
In this work, In-doped ZnO films on glass substrate were grown by spray pyrolysis method at 600 °C. The samples were annealed under N2 atmosphere. XRD indicates that (0002) orientations are clearly observed with increasing annealing temperature. Values of FWHM become large with increasing annealing temperature. This means that grain sizes become small with increasing annealing temperature. Photoluminescence intensity increases with increasing annealing temperature.
[1] K. Yoshino et al. J. Mater. Sci. 16 (2005) 403. |