Study of preferred orientation of zinc oxide films on the 64°LiNbO3 substrates and their applications as liquid sensors

The preferred (002) orientation of zinc oxide (ZnO) films has been grown and demonstrated on 64°LiNbO3 substrates using a rf magnetron sputtering system. The film orientations and crystallinity are strongly dependent on the rf power, total chamber pressure, ratio of argon to oxygen, and substrate temperature. We investigated the crystalline structure of the films by x-ray diffraction and scanning electron microscopy. Highly oriented (002) films were obtained under a total chamber pressure of 1.33Pa, containing 40% oxygen and 60% argon, and a substrate temperature around 120°C. Love-wave devices based on this structure (ZnO∕IDTs∕64°LiNbO3) are presented.