Deposition of LiNbO3 thin films on diamond/Si(100) substrates for high frequency surface acoustic wave filter applications

Filters operating at high frequencies up to gigahertz are required in telecommunications in order to increase the rate of data transmission. The goal of this research is to produce gigahertz electronical filters with low insertion loss for front-end radio frequency filters by fabricating LiNbO3 thin film surface acoustic wave filter devices on diamond-coated silicon chips. In this paper, the deposition of LiNbO3 thin films on diamond/Si(100) substrates by a metal-organic decomposition process is reported. X-ray diffraction analysis shows that the films are highly textured polycrystalline LiNbO3 with a (012) orientation. Planview and cross-section scanning electron microscopy indicate that the LiNbO3 thin films have dense, smooth surfaces without cracks and pores, and they adhere very well to the diamond/Si(100) substrates. The grain size is in the range of approx. 0.2-0.5 μm. Atomic force microscopy reveals an average surface roughness of about 25 nm.