Oxides with perovskite crystal structure such as SrTiO3 are important candidates for ultrathin gate oxides because of their large DC dielectric constant. When SrTiO3 is deposited directly on Si, an amorphous non-stoichiometric interfacial layer is usually formed during the later stages of growth, which reduces the specific capacitance and is therefore undesirable. We have performed deep-UV spectroscopic ellipsometry measurements from 0.7 to 6.6 eV of SrTiO3 films grown on Si by MBE. This technique is very well suited to determine the thickness of SrTiO3 films between 75 and 200 Å. For thinner films, refractive index and thickness cannot be determined independently. Ellipsometry measures the total thickness (SrTiO3 plus amorphous interfacial layer). There is no signature in the data that can be used to determine the SrTiO3 and interfacial layer thicknesses independently. We find that the effective refractive index (averaged over the crystalline SrTiO3 and the interfacial layer) decreases with decreasing thickness due to the increasing importance of the interfacial layer, but the overall critical-points due to interband transitions are not eliminated, therefore the electronic structure stays mostly intact.

For a Si(100)2×1 surface exposed to oxygen, there is a transition from etching (“active” oxidation via removal of SiO) to “passive” oxidation (buildup of an oxide film) with decreasing surface temperature. The transition depends sensitively on a competition between SiO desorption, and oxide island formation. We analyze these processes utilizing both ab-initio quantum chemistry studies of key energetics and lattice-gas models for the cooperative behavior.

In today's main crystalline silicon (c-Si) applications in MOS (metal-oxide-silicon), MIS (metalinsulator-semiconductor) or SIS (Semiconductor-Insulator-Semiconductor), the growing of the oxide layer plays the main role, dictating the device performances, in particular if it has to be grown by a low temperature process. Of fundamental importance is the SiO2 interface with the c-Si. A very low defect density interface is desirable so that the number of trapping states can be reduced and the devices performance optimised.

A two step low temperature oxidation process is proposed. The process consists of growing first a layer of oxide by a wet process and then treating the grown oxide with an oxygen plasma. The oxygen ions from the plasma bombard the oxide causing compaction of the oxide and a decrease in the interface roughness and defect density.

Infrared spectroscopy and spectroscopic ellipsometry measurements were performed on the samples to determine the oxide thickness, optical and structural properties. SIS structures were built and capacitance measurements were performed under dark and illuminated conditions from which were inferred the interface defect density and correlated with the oxide growth process.

The structure of c-axis oriented [YBa2Cu3O7−(YBCO) N / PrBa2Cu3O7 (PBCO)M/1000Å superlattices with N ranging between 1 and 12 and M=5 unit cells, grown by high oxygen pressure sputtering on (100) SrTiO3 substrates, is analyzed by x-ray diffraction (XRD) and highresolution transmission electron microscopy (HREM). The XRD spectra refinement shows epitaxial strain for YBCO thickness below 4 unit cells. For larger YBCO layer thickness, stress relaxes and step disorder builds up. HREM observations show sharp and flat interfaces between substrate and superlattice stack. The only observable defects are isolated steps or a-axis oriented domains in relaxed samples. The results of both structural tools are compared.

We studied the epitaxial growth of CeO2 thin films deposited onto MgO(100), YSZ(100) and Al2O3(1102 ) (r-plane sapphire) substrates by reactive dc magnetron sputtering of a Ce metal target in an Ar/O2 plasma. The crystalline quality and biaxial alignment of the films was determined using x-ray diffraction techniques (θ-2θ, ω-scans, pole figures, ø-scans). The CeO2/MgO(100) and CeO2/Al2O3(1102) epitaxy was evident at 600°C and developed to nearly perfect biaxial alignment at 850°C with Δø = 5° and 9° respectively. The CeO2/YSZ (100) epitaxy occurred below 300°C while deposition at ≥ 650°C led to single-crystal quality CeO2 films with Δø = 0.2°.

Experimental results are shown for the structural and stress behaviors of c-axis oriented barium hexaferrite films on c-plane sapphire (Al2O3) substrates as a function of oxygen growth pressure and film thickness. It is shown that films deposited at 20 mTorr crack and delaminate at thicknesses above 15 µm, but that evidence for these large stresses is not apparent in either substrate curvature measurements or distortion of the c-axis lattice constant for thinner films (< 2 µm). In contrast, films (< 4 µm) deposited at 300 mTorr show large substrate curvatures that relax with increasing film thickness, in tandem with the formation of first large outgrowths, and then polycrystalline grains as the original c-axis film texture is randomized. Correlations between these observations are made to explain the complex evolution of properties in these films.

Using solution chemistry, epitaxial films of rare-earth oxides of the general formula RE2O3 (where RE = Sm to Lu) were prepared on cubic-textured nickel tapes. Solutions of metal methoxyethoxides or metal acetate/methoxyethoxides in 2-methoxyethanol were used to coat rolltextured nickel tapes using either spin-coating or dip-coating. Coated tapes were subsequently heated in a reducing atmosphere at temperatures between 950 °C and 1160 °C for varying lengths of time. Film quality was determined using X-ray diffraction and electron and surface probe microscopy. Films were found to be oriented both in and out-of-plane of the substrate, free of pinholes and gross defects, and of sufficient quality for use as substrates for high Tc, superconductors.

Epitaxial buffer layers of Ho2O3 on biaxially textured nickel were fabricated using a chelate (acetic acid) solution route as an alternative to the 2-methoxyethanol solution approach, which has demonstrated good texturing characteristics. Plan-view SEM studies of the films as a function of heat treatment temperature have shown that the holmium oxide film pyrolyzes into an open structure with a high level of interconnected porosity before densification, without significant film shrinkage in the thickness direction. Consolidation of the film started around 900°C along the backbone of the open structure and sintering to a dense film of uniform small crystallites (∼25 nm) was observed at higher temperature. The as-received nickel tapes displayed significant surface damage with a roughness on the order of 1000 Å. Electron backscattering analysis suggests that only 65% of the nickel grains were aligned along the (100) axis within 5°. Finally, STM studies of the nickel substrate have shown that small nickel oxide crystallites were formed on the surface when the substrate is in contact with air.