Epitaxial lead(magnesium(1/3)niobium(2/3))oxygen(3)-lead titanate thin films.

摘要

Pulsed laser deposition was used to deposit oxide ferroelectric heterostructures on (001) oriented LaAlO{dollar}sb3{dollar} and SrTiO{dollar}sb3{dollar} single crystal substrates. SrRuO{dollar}sb3{dollar} was used as the bottom electrode, while the ferroelectric layer was either (Pb,La)(Mn,Ti)O{dollar}sb3{dollar} (PLMT) or {dollar}rm Pb(Mgsb{lcub}1/3{rcub}Nbsb{lcub}2/3{rcub})Osb3{dollar}-PbTiO{dollar}sb3{dollar} (70/30) (PMN-PT). The latter compound for the focus of this thesis given the recent discovery of anomalously large piezoelectric coefficients in single crystals of this material.; It was found that the structural, electrical, and morphological characteristics of the SrRuO{dollar}sb3{dollar} electrodes were sensitive to bombardment during growth. In general, growth conditions providing strong energetic bombardment resulted in material with lattice constants extended by as much as 4% in the out-of-plane direction. Accompanying the extended lattice constants was an increased electrical resistivity and a coarsened surface microstructure.; The results of the PMN-PT processing study were largely analogous to those of ceramic and single-crystal investigations, i.e., great difficulty was encountered achieving phase-pure material with good electrical properties. In general, when depositing from lead-rich targets {dollar}(ge{dollar}25% PbO), perovskite, Pb-rich, and Pb-deficient material could be simultaneously observed in a single sample. Electrical analysis of the films revealed that the best electrical properties occurred for samples containing small amounts of second phases, either Pb-rich or deficient. The very best samples exhibited bulk transition temperatures, room temperature dielectric constants greater than 1500, remanent polarizations of 20 {dollar}mu{dollar}C/cm{dollar}sp2,{dollar} and peak x-ray line widths of 0.4{dollar}spcirc, 0.5spcirc,{dollar} and 0.8{dollar}spcirc{dollar} for the 2{dollar}theta, omega,{dollar} and {dollar}phi{dollar}-x-ray circles respectively.; Deposition of epitaxial films was also possible from targets containing very small quantities of PbO ({dollar}sim{dollar}3%) at temperatures below 600{dollar}spcirc{dollar}C. Under these conditions phase-pure samples with large electrical resistivities could be achieved. For these samples, energetic bombardment was required to optimize the structural and electrical properties. However, when subjected to heavy bombardment during growth, the same lattice constant extension observed for SrRuO{dollar}sb3{dollar} was encountered.; In-situ field dependent x-ray diffraction and the wafer-flexure method were used to determine the longitudinal (d{dollar}sb{lcub}33{rcub}){dollar} and the transverse (d{dollar}sb{lcub}31{rcub}){dollar} piezoelectric coefficients of the PMN-PT respectively. Values of 350 pC/N (d{dollar}sb{lcub}33{rcub}){dollar} and {dollar}-{dollar}180 pC/N (d{dollar}sb{lcub}31{rcub}){dollar} were determined.