| "Geometric ferroelectrics" form an interesting, albeit not well-studied, subset of ferroelectric materials. The term "geometric ferroelectrics" is used for compounds that exhibit ferroelectricity owing to a simple relaxation of frustrations in the unit cell geometry, and not as a result of either a second-order Jahn-Teller distortion (SOJT) or a cooperative lone pair displacive mechanism. The structure-property relationships in such materials has not been investigated in depth owing to the limited number of known materials that adopt the "geometric ferroelectric" structures. This thesis is concerned with the development of a synthesis method that will allow one to realize materials in these structures over wider composition spaces.; Thin film synthesis of two classes of oxide geometric ferroelectric materials---ABO 3 compounds adopting the layered hexagonal LuMnO3 structure (h-REMnO3) and A4B4O 14 (Sr2Nb2O7) compounds adopting the [110]-layered perovskite structure, which both compete in stability with the close-packed perovskite (p-REMnO3 or SrNbO3) structure---is the focus of this thesis. Materials in both the classes were grown by Pulsed Laser Deposition (PLD) on various substrates and under various process conditions (temperature, energy, process gas type/pressure...) and characterized mainly by X-ray diffraction.; The temperature, pressure, and nature of the ambient gas are the primary influence on the phase (and orientation) selected during the thin film growth of materials in the SrNbOy family. In N2 ambients, when the partial pressure of O2 is very low, reduction of the Nb cation to the 4+ state resulted in the perovskite SrNbO3 formation on SrTiO3(100) and (110), as well as MgO(100) and (111). On SrTiO 3, cube-on-cube epitaxy was observed, while on MgO, polycrystalline films were obtained. On the other hand, O2 ambients favored the Nb cation in its fully oxidized pentavalent state, resulting in formation of (110)-layered perovskite Sr2Nb2O7. On SrTiO3(110) substrates, lower oxygen pressures and higher temperatures led to epitaxial (010)-oriented Sr2Nb2O7, while higher oxygen pressures and lower temperatures resulted in textured (001)-oriented Sr2Nb2O7. The crystalline quality of the Sr2Nb2O7 was strongly decreased when deposited upon SrTiO3(100), which yielded only weak diffraction from Sr2Nb2O7 film in the XRD patterns. (Abstract shortened by UMI.)... |
