Orientated nano grain growth and effect of annealing on grain size in LiTaO3 thin films deposited by sol–gel technique

This paper reports the deposition of lithium tantalate (LiTaO3) thin films by sol–gel process. Thin films were deposited on three different substrates, viz. Pt–Si [Pt(1 1 1)/TiO2/SiO2/Si(1 0 0)], Si(1 1 1), and sapphire(0 0 6) by spin coating. The influence of lattice mismatch and packing structure of atoms on the orientation of the film was investigated. In order to study the influence of annealing temperature on crystallinity, microstructure, grain size, and roughness, the films were first annealed at 650 °C, and subsequently annealed at 1000 °C. From XRD and AFM pictures it is confirmed that nano-oriented grain growth occurs only on sapphire substrate at the annealing temperature 650 °C, and the grain size increases from 50 to 200 nm when the annealing temperature is increased to 1000 °C. The surface roughness of the film increases when the annealing temperature increases. In the case of the Pt–Si substrate, prominent grain growth occurs at 1000 °C, but the grains are randomly oriented due to the lattice mismatch and packing structure of atoms. But in case of silicon substrate, packing structure of atoms plays an important role, rather than the lattice mismatch.