Yittria stabilized zirconia (YSZ) has long been of interest as a promising material for nuclear energy applications. It is the cubic form of zirconium oxide stabilized at room temperature by the addition of yttria. Previous studies of radiation damage in YSZ focused primarily on microstructural changes in the bulk or in the near surface layer whereas irradiation induced changes on the surface received little attention. Here we use atomic force microscopy, AFM, to study the fluence-dependent generation of surface modifications to YSZ due to 150 keV Ar+ ion implantation at fluences from 3×1015 to 1×1017 ions/cm2. The microstructural changes in the near surface region were previously investigated by Rutherford backscattering spectrometry in channeling geometry (RBS/C). Further, we investigated implantation in (100), (110), and (111) oriented single crystals of YSZ to explore differences in crystal orientation sensitivity to damage to ion irradiation. At the highest fluence, a dense packing of large round surface hillocks was observed. The ion induced surface modifications revealed by AFM differ slightly from the bulk lattice damage measured by RBS, although both indicate that under these implantation conditions, the (110) oriented crystal shows the most radiation damage resistance. The mean size of the hillocks scaled with concentration of implanted Ar atoms.

Scanning force microscopy (SFM) phase imaging provides a powerful method for directly studying and comparing phase segregation in fuel cell membrane materials due to different preparation and under different temperature and humidity exposures. In this work, we explored two parameters that can influence phase segregation: the properties of the solvents used in casting membrane films and how these solvents alter phase segregation after exposure to boiling water as a function of time. SFM was used under ambient conditions to image phase segregation in Nafion samples prepared using five different solvents. Samples were then subjected to water vapor maintained at 100°C for periods ranging from 30 minutes to three hours and re-imaged using the same phase imaging conditions. SFM shows what appears to be an increase in phase segregation as a function of solvent polarity that changes as a function of water exposure.

We have achieved what we believe to be the first atomic resolution STM images for a uranium compound taken at room temperature. The a, b, and c lattice parameters in the images confirm that the USb2 crystals cleave on the (001) basal plane as expected. The a and b dimensions were equal, with the atoms arranged in a cubic pattern. Our calculations indicate a symmetric cut between Sb planes to be the most favorable cleavage plane and U atoms to be responsible for most of the DOS measured by STM. Some strange features observed in the STM will be discussed in conjunction with ab initio calculations.

Uranium is an extremely important material for commercial and military applications (i.e. nuclear power, nuclear weapons, conventional weapons, and armor systems) and, like a number of other materials, is vulnerable to corrosion by environmental gases that affect their properties, leading to component degradation, shortened lifetimes and materials failure. For uranium this is particularly true in the case of corrosion by hydrogen. A fundamental understanding of the corrosion process at the nucleation stage is of critical importance. The goal of this work is to study the role of common chemical impurities in uranium with initiation sites for the formation of destructive hydride blisters. Samples were implanted with various ions, annealed under vacuum at 200°C, than exposed to one atm of ultra-pure hydrogen. Scanning force microscopy surface potential imaging was used to characterize the structure and corresponding electrical properties of polycrystalline uranium surfaces that resulted from the implantation of different suspect atoms after exposure to hydrogen gas. Surface potential images revealed features related to different oxide structures and hydride spots/blisters as well as other features not obvious in the corresponding topograph. In the surface potential images, blisters appear as bright (higher potential) features in sharp contrast to the uranium oxide background. Often a possible inclusion was observed in the center of a blister. Blister formation did not appear to correlate with implantation of any specific specie, however, distinct differences were seen between implanted and non implanted sides of the same sample.

We have grown thin films of La0.84Sr0.16MnO3 on SrTiO3 (100), MgO (100), CeO2 (100)/Al2O3, and (100) oriented yttria-stabilized zirconia (YSZ) substrates by using a 90°off-axis RF magnetron sputtering deposition. X-ray diffraction analysis and ion beam channeling experiments reveal that the deposited films grow epitaxially on SrTiO3, biaxially textured on MgO, and highly textured on YSZ. Scanning tunneling microscopy reveals that the thin films possess extremely smooth surfaces.

Ion-assisted, ion-beam sputter deposition is used to obtain (00l) biaxially oriented films of cubic yttria-stabilized-zirconia (YSZ) on polycrystalline metal substrates. Yttrium-barium-copper-oxide (YBCO) is then heteroepitaxially-pulse-laser deposited onto the YSZ. Phi scans of the films show the full-width-half maxima of the YSZ (202) and the YBCO (103) reflections to be 14° and 10° respectively. Our best dc transport critical current density measurement for the YBCO is 800,000 A/cm2 at 75K and 0T. At 75K, the total dc transport current in a 1 cm wide YBCO film is 23 A.

The evolution of the growth morphology of thin films of InN on (00.1) sapphire and on (00.1) sapphire prenudeated by a layer of AIN have been followed as a function of the thickness of the InN overlayer. The InN thin films and the AIN nucleation layers were deposited by reactive magnetron sputtering and first characterized by X-ray scattering, profilometry, and electrical transport. These AIN-nucleated InN films displayed heteroepitaxial grains, and high Hall mobility -even in the limit of InN overlayer on the order of 20-40Å. In parallel, InN films of varying thickness were grown directly onto (00.1) sapphire. These films showed a mixture of textured and heteroepitaxial grains, and lower Hall mobility. Atomic force and scanning tunneling microscopy studies have focussed on the morphology of the InN films with thicknesses: (a) much smaller than the AIN nucleation layer; and, (b) near the morphological transition that occurs at ∼1μm and has been attributed to the crossover from a 2D to a 3D growth mechanism. Additional correlations of X-ray structural coherence with growth mode are also examined.

Control of the in-plane epitaxial alignment of c-axis YBa2Cu3O7−δ (YBCO) films on yttria-stabilized zirconia (YSZ) substrates is necessary for achieving optimal transport properties. We have used pulsed laser deposition to grow homoepitaxial YSZ and heteroepitaxial CeO2 on YSZ single crystal substrates. This procedure dramatically improves the epitaxy of YBCO and reduces the number of low and high angle grain boundaries. We have also studied the effects of preparing the YSZ growth surface with approximately monolayer amounts of CuO, Y2O3, BaO, and BaZrO3 to determine the effects these compositional variations have on the subsequent YBCO epitaxy. CuO, Y2O3, and BaZrO3 induce an in-plane crystallography of YBCO distinct from that initiated with BaO. Both homoepitaxy and monolayer depositions may be carried out in situ and are simple and effective for controlling the epitaxy and electrical properties of YBCO on YSZ. The effects of substrate temperature, oxygen pressure, and yttria content have also been studied.

The residual surface resistance of a number of films of YBa2Cu3O7−x, prepared by off-axis sputtering onto MgO substrates, has been measured using a parallel-plate resonator technique. Deposition conditions were kept constant, apart from the substrate temperature. There is no correlation between surface resistance and other important microscopic parameters, such as Tc and c-axis lattice parameter. There is, however, a trend to higher Rs with increasing volume fraction of in-plane misoriented material, although the correlation is not perfect. Furthermore, we have found that most of the misoriented material is localized at the film substrate interface and, therefore, is probably not responsible for most of the RF losses. The data suggest that at higher deposition temperatures, there is an increasing tendency for 45° misoriented material to appear in the films, and a significant fraction of this material may be present closer to the free film surface. Scanning Tunneling Microscopy (STM) qualitatively supports this conclusion.