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Optical properties of PbTiO3 films deposited by sol-gel process and pulsed laser deposition: a comparison

Lead titanate PbTiO3(PT) thin films were prepared on single-crystal MgO(100) substrates by sol-gel process (SG) and pulsed laser deposition (PLD) techniques. The SG coating solutions were synthesized from lead (II) acetate, titanium isopropoxide precursors using acetic acid and diethanolamine (DEA). The SG films were spin coated at 2000 rpm, dried in air at 350 degree(s)C and rapid thermally annealed at between 400-650 degree(s)C temperature range. PLD films were grown at 2x10-6 Torr chamber pressure in flowing oxygen and at the substrate temperature of 600 degree(s)C. The films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and scanning spectrophotometry. The optical properties of the PT films were evaluated from spectral transmittance and reflectance measurements. Optical and structural properties of SG and PLD thin films grown at 600 degree(s)C substrate temperature were compared. XRD analysis indicates that PLD films grow strongly textured on MgO(100) substrate. In contrast, SG films were randomly oriented. SEM showed that the surface of the SG PT films heat treated at above 600 degree(s)C had smaller grains. In contrast PLD grown films had a well-developed dense and uniform grain structure with larger grain size. The optical constants such as refractive index (n), extinction coefficient (k) and optical band gap (Eg) values were found to depend on the preparation techniques. The optical band gap values are in the range of 2.98-3.24 eV depending on the deposition method.