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Elasticity of high coupling relaxor-ferroelectric lead zinc niobate-lead titanate crystals J. Appl. Phys. 98, 094113 (2005); 10.1063/1.2127127Cut directions for the optimization of piezoelectric coefficients of lead magnesium niobate-lead titanate ferroelectric crystals

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This communication describes a technique used to pattern oxide thin layers using microcontact printing (μCP) and sol-gel deposition. The technique involves μCP of self-assembled monolayers (SAM's) of alkylsiloxane on various substrates (SiO2/Si, sapphire, ITO, and glass), followed by deposition of oxide thin layers from sol-gel precursors. Delamination of oxide layers from SAM-derivatized regions allows selective deposition of crystalline dielectric oxide layers on underivatized regions. To demonstrate the viability of this technique for integrated microelectronics and optics applications, patterned (Pb,La)TiO3 (PLT) and LiNbO3 layers were deposited on sapphire, silicon, and indium tin oxide (ITO) substrates. Use of lattice-matched substrates allows lithography-free deposition of patterned heteroepitaxial oxide layers. Strip waveguides of heteroepitaxial LiNbO3 with 4 μm lateral dimensions were fabricated on sapphire. Dielectric measurements for patterned PLT thin layers on ITO are also reported.

Lead zirconate titanate (PZT 40/60) thin films were fabricated on electroded silicon wafers using chemical solution deposition. Two different chelating agents, acetic acid and acetylacetone, were used in the synthesis of the precursor solutions. The microstructure of the acetylacetone-derived film was characterized by nucleation at the platinum electrode and a columnar growth morphology (˜100−200 nm lateral grain size). In contrast, the acetic acid-derived film was characterized by both columnar grains nucleated at the electrode, and larger (˜1 μm) grains nucleated at the surface of the film. Using Fourier transform infrared (FTIR) diffuse reflectance spectroscopy, we also noted that the pyrolysis behavior of the films was dependent on the chelating agent employed. The acetylacetone-derived films, which displayed only one nucleation event, were also characterized by a higher pyrolysis temperature than the acetic acid-derived films. Previously, microstructural differences of this nature were attributed to variations in “precursor structure.” In this paper, we discuss an alternative mechanism for the observed microstructural variations in films prepared from different solution precursors. In the model proposed, we discuss how changes in film pyrolysis temperature result in a change in film crystallization temperature, and hence, a change in the effective driving force for crystallization. We show how the change in crystallization driving force is expected to impact the thin film microstructure due to the accompanying variations that occur in the barrier heights for interface (lower electrode) and surface nucleation. A standard approach to nucleation in glasses is used as the basis of the proposed model. Finally, we also discuss how the model can be used to understand the observed effects of heating rate and thickness on the microstructure of solution-derived thin films.