Study on the Crystal Growth Mechanism of ZnO Films Fabricated Via Nitrogen Mediated Crystallization.

Abstract

ZnO-based TCO has attracted much attention because it has potential to replace Sndoped In2O3 (ITO) due to its low toxicity and abundance in nature. We have demonstrated a novel method to fabricate high quality ZnO films via nitrogen mediated crystallization (NMC) method [1]. Utilizing the NMC ZnO as buffer layers, ZnO:Al films with low resistivity have been obtained. Here we have studied the growth mechanism of the NMC ZnO at the early stages of growth by means of height-height correlation function analysis of the surface morphology that derives lateral correlation length ξ. NMC-ZnO films were fabricated on quartz glass substrates by RF magnetron sputtering using Ar-N2 gas at the substrate temperature of 300°C. Figure 1 shows ξ of NMC ZnO as a function of the deposition time (t). At the early stage of crystal growth until t= 12 sec, the nuclei are sparsely distributed, being indicated by the decrease in ξ. At t= 15 sec, ξ reaches the minimum where the nuclei are uniformly distributed over the surface and the crystallite nuclei start to grow, which can be seen from the increase in ξ. The value of ξ at NMC-ZnO thickness of 10 nm was found to be 0.42 μm that is significantly longer than that for a conventional ZnO fabricated without nitrogen (0.2 μm), indicating that nitrogen has obvious effects on the nucleation and growth of ZnO. The detail will be discussed at the conference. *, K. Oshikawa, H. Seo, D. Yamashi ta, K. Kamataki, G. Uchida, K. Koga, M. Shiratani, N. Itagaki Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka 819-0395, Japan PRESTO, Japan Science and Technology Agency, Tokyo 102-0075, Japan