Structures and opto-electrical characteristics of ZITO thin films

Abstract

Transparent conductive oxide (TCO) thin film has received extensive attention all the time due to its potential applications in various opto-electronic devices [1–2]. Among various TCO films, indium-doped ZnO (IZO) and indium tin oxide (ITO) thin films have been widely investigated due to their particular optical and electrical properties [3–4]. Regardless of ZnO-based or ITO films, the studies were focused on the doping effects and crystallized mechanisms on materials characteristics were rarely explored. To achieve better conductivity, the multi-compound films were deposited by sputtering, such as ZnO-SnO2-In2O3, In2O3-ZnO and In2O3-SnO2 films etc [5–6]. However, the investigation of sol-gel derived multi-compound ZITO (ZnO combined ITO) film has never been studied. For these reasons, the ZITO films were synthesized to investigate the effects of ITO contents and the effect of temperature on structural characteristics, the optical transmittance and electrical properties. To obtain the aqueous solution of ZITO, ZnO and ITO solutions were firstly prepared by sol-gel method, respectively. All clear solutions were mixed with various volume ratios (ZnO : ITO = 1:1 and 2:1). Hereafter, the films will be designated according to volume ratio of ZnO and ITO as Z1ITO and Z2ITO. Subsequently, this resultant solution was deposited onto the silica-glass substrates using a spin coating. After that, the samples were dried at 200 oC to evaporate the solvent and remove organic residuals (non-stop until to desired thickness of 150 nm). Finally, the samples were performed at 600~700 oC for 1 hour under O2 atmosphere.