Preparation and properties of electroceramics films using the metallo-organic decomposition process
Abstract
The application of metallo-organic decomposition (MOD) technology to the fabrication of useful thin films in a wide range of materials systems was investigated. The materials properties were studied closely and correlated with crystal structures, microstructures and the materials processing. MOD Pt films 50 nm thick on various substrates were formed at temperatures as low as 350$\sp\circ$C. Films fired at 600$\sp\circ$C showed a texture structure with grains oriented with their $\lbrack111\rbrack$ axis perpendicular to the substrate surface. The electrical resistivity measured by the Van der Pauw method was 30 $\mu\Omega$cm. MOD ITO transparent conductor films with composition In$\sb{1.91}$Sn$\sb{0.09}$O$\sb3$ were shown to be n-type semiconductors. The energy gap was estimated to be 6.2 meV from the measurements of the temperature dependence of charge density and the optical spectrum. The relatively low Hall mobility (about 2cm$\sp2$V$\sp{-1}$s$\sp{-1}$) at room temperature in the fine grain size films (10-20 nm) was related to grain boundary scattering. Ferroelectric BaTiO$\sb3$, PbTiO$\sb3$ and (PbSr)TiO$\sb3$ films from MOD technology were studied. It was found that in this category the basic materials properties such as polarization and its reversal, which were mostly explained by their crystal structure, were closely linked with film's microstructures, which were in turn controlled by the materials processing. Both crystal structure changes due to the smaller grain size and the presence of an amorphous phase inside the films affected the properties of these ferroelectric films. MOD PLZT (8/65/35) films (0.4 $\mu$m thickness) on sapphire showed a birefringence shift of 0.0014 at an applied electric field of 2kV/cm. The hysteresis loop of the $\Delta$($\Delta n$)-E plot also indicated the presence of memory characteristics. The quadratic electro-optic coefficient was 0.5 $\times$ 10$\sp{-16}$(m/V)$\sp2$, and the linear electro-optic coefficient at 632.8 nm was 0.30 $\times$ 10$\sp{-10}$m/V, which is larger than that of LiNbO$\sb3$ commonly used for electrooptic waveguiding devices. MOD YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$ superconducting films on sapphire showed a wide transition temperature of 30K (from onset to zero resistivity temperature). The TEM study indicated that there was a micro-segregation of chemical composition inside the films. Producing films with more uniform distribution of composition will improve the electrical properties of MOD superconducting films.
Degree
Ph.D.
Advisors
Vest, Purdue University.
Subject Area
Materials science
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.