Physical Properties of RF-Sputtered ZnO Thin Films: Effects of Two-Step Deposition

Abstract

Polycrystalline ZnO thin films are deposited on SiO 2 /Si(100) substrates by using RF magnetron sputtering. A novel two-step deposition technique for improving both the c -axis preferred orientation and the resistivity of the ZnO films is proposed. The key procedure in the proposed method is to control the amount of oxygen in the deposition step; the 1 st -deposition is done for 30 min without oxygen at 100 W, and the 2 nd -deposition is done with oxygen in the O 2 /(Ar+O 2 ) range of 10 sim 50 \%. The two-step deposited ZnO films reveal a strongly c -axis preferred orientation (the corresponding texture coefficient of almost 100 \%) and a high resistivity (up to approximately 2.5 imes 10 9 Omega cm). The crystallite size of ZnO is also noticeably increased by thermal-annealing. Raman studies on ZnO films give some reasonable explanations for the effects of the two-step deposition and the thermal treatment on the film properties.