The structural and optical characteristics of nearly stoichiometric lithium tantalate films have been studied. The LiTaO3 films were prepared by RF magnetron sputtering method and the phase was confirmed by powder X-ray diffraction. The optical properties were obtained from optical transmittance spectroscopy in UV-vis.-NIR range. The electronic band gap structure were determined from the fundamental absorption edge in the UV region. The evolution of defect structures caused by varying composition and post-growth processing has been evaluated from the optical absorption measurements. Optical absorption studies showed that the UV absorption edge is very sensitive to the composition of LiTaO3 films. The absorption features in the UV range indicate the discrete nature of conduction band and the allowed energy levels in the forbidden gap appeared due to surface defects.
Multilayer lithium tantalate thin films have been successfully prepared on Pt/Ti/SiO2/Si(100) substrate using sol-gel and spin-coating method. Polycrystalline perovskite films were obtained through pyrolysis at 400°C and subsequent calcination at various temperatures from 500°C to 700°C for 1h, which were optimized by means of X-ray diffraction, Raman spectroscopy and thermal analysis. The morphology on the top surface and fractured cross section of LT films was observed by a field-emission scanning electron microscope. The 300 nm thick LT film annealed at 650°C exhibited a dielectric constant of 19.8 and a loss tangent of 0.06 at10KHz.
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