We demonstrated short segments of a superconducting wire that meets or exceeds performance requirements for many large-scale applications of high-temperature superconducting materials, especially those requiring a high supercurrent and/or a high engineering critical current density in applied magnetic fields. The performance requirements for these varied applications were met in 3-micrometer-thick YBa2Cu3O(7-delta) films epitaxially grown via pulsed laser ablation on rolling assisted biaxially textured substrates. Enhancements of the critical current in self-field as well as excellent retention of this current in high applied magnetic fields were achieved in the thick films via incorporation of a periodic array of extended columnar defects, composed of self-aligned nanodots of nonsuperconducting material extending through the entire thickness of the film. These columnar defects are highly effective in pinning the superconducting vortices or flux lines, thereby resulting in the substantially enhanced performance of this wire.

In-plane-aligned, c axis-oriented YBa, Cu, O, (YBCO) films with superconducting critical current densities J, as high as 700,000 amperes per square centimeter at 77 kelvin have been grown on thermomechanically rolled-textured nickel (001) tapes by pulsedlaser deposition. Epitaxial growth of oxide buffer layers directly on biaxially textured nickel, formed by recrystallization of cold-rolled pure nickel, made possible the growth of YBCO films 1.5 micrometers thick with superconducting properties that are comparable to those observed for epitaxial films on single-crystal oxide substrates. This result represents a viable approach for the production of long superconducting tapes for high-current, high-field applications at 77 kelvin.Since the discovery of high-temperature superconductivity (HTS) in cuprate materials, substantial efforts have focused on developing a high-current superconducting wire technology for applications at 77 K (1, 2). Early in these efforts it was observed that randomly oriented polycrystalline HTS materials have critical current densities, J,, (500 A/cm2. In contrast, oriented YBCO thin films grown epitaxially on single-crystal oxide substrates, such as SrTiO, (OOl), exhibit J, values >1 MA/cm2 at 77 K (3). This huge difference between randomly oriented HTS ceramics and single crystal-like epitaxial films is directly related to the misorientation angles at the grain boundaries in polycrystalline materials. Values for J, across a grain boundary decrease significantly as the misorientation angle increases, with weak-link behavior observed for misorientation angles at the grain boundaries greater than -10" (4-12). In order to achieve high J, values (-lo5 to lo6 A/cm2, 77 K), the crystallographic orientation of the HTS superconducting wire or tape must have a high degree of both in-plane and out-of-plane grain alignment over the conductor's entire length. Ideally, this would be achieved with YBCO, because the limits for dissipation-free current at 77 K in an applied magnetic field are most favorable for this material (1 3, 14).One approach to producing a high-J, HTS tape is to deposit a thick epitaxial film on a substrate material that has a high degree of in-plane and out-of-plane crystallographic texture and can be produced in long lengths. Epitaxial HTS films on singlecrystal oxides satisfy the requirements for high J,, but it is not feasible to produce long lengths of these substrates. Recent efforts have focused on the use of ion beam-assisted deposition (IBAD) to achieve inplane alignment of oxide buffer layers on polycrystalline metal substrates for subsequent epitaxial growth of . Indeed, a modest degree of in-plane texture for c axis-oriented YBCO films made by IBAD results in a significant increase in J,, with values ranging from lo5 to lo6 A/cm2 at 77 K. However, IBAD techniques have limitations, including the relatively low de~osition rates associated with the IBAD buffer layers as well as difficulties in consistently producing in-plane crystallographic alignment of less than lo0, tha...

Crystal silicon (c-Si) film photovoltaics (PV) fabricated on inexpensive substrates could retain the desirable qualities of silicon wafer PV-including high efficiency and abundant environmentallybenign raw materials-at a fraction of the cost. We report two related advances toward film c-Si PV on inexpensive metal foils. First, we grow heteroepitaxial silicon solar cells on 2 kinds of singlecrystal Al 2 O 3 layers from silane gas, using the rapid and scalable hot-wire chemical vapor deposition technique. Second, we fabricate heteroepitaxial c-Si layers on large-grained, cube-textured NiW metal foils coated with Al 2 O 3 . In both experiments, the deposition temperature is held below 840 C, compatible with low fabrication costs. The film c-Si solar cells are fabricated on both single-crystal sapphire wafer substrates and single-crystal g-Al 2 O 3 -buffered SrTiO 3 wafer substrates. We achieve $400 mV of open-circuit voltage despite crystallographic defects caused by lattice mismatch between the silicon and underlying substrate. With improved epitaxy and defect passivation, it is likely that the voltages can be improved further. On the inexpensive NiW metal foils, we grow MgO and g-Al 2 O 3 buffer layers before depositing silicon. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) confirm that the silicon layers are epitaxial and retain the $50 mm grain size and biaxial orientation of the foil substrate. With the addition of lighttrapping, >15% film c-Si PV on metal foils is achievable.Crystal silicon semiconductors dominate the existing photovoltaic (PV) industry because the Si wafer is a proven and well-understood industrial commodity: Si is abundant, environmentally benign, and capable of high solar conversion efficiencies. However, the energyintensive, inefficient and expensive processes that turn sand into a crystal silicon (c-Si) wafer hamper efforts to dramatically reduce PV costs. To circumvent the costly wafer fabrication step, it would be ideal to grow a film of PV-quality silicon, perhaps 2 to 20 microns thick, directly from silane gas onto an inexpensive substrate. With excellent light trapping, solar cell efficiencies above 15% are possible. 1 For high conversion efficiency, the silicon layer must have crystal quality high enough for photogenerated minority carriers to diffuse to the collecting contacts before recombining, 2 although the films are likely to be polycrystalline to reduce costs. These polycrystalline Si films will require grain sizes considerably larger than the film

Optical surfaces such as mirrors and windows that are exposed to outdoor environmental conditions are susceptible to dust buildup and water condensation. The application of transparent superhydrophobic coatings on optical surfaces can improve outdoor performance via a 'self-cleaning' effect similar to the Lotus effect. The contact angle (CA) of water droplets on a typical hydrophobic flat surface varies from 100° to 120°. Adding roughness or microtexture to a hydrophobic surface leads to an enhancement of hydrophobicity and the CA can be increased to a value in the range of 160°-175°. This result is remarkable because such behavior cannot be explained using surface chemistry alone. When surface features are on the order of 100 nm or smaller, they exhibit superhydrophobic behavior and maintain their optical transparency. In this work we discuss our results on transparent superhydrophobic coatings that can be applied across large surface areas. We have used functionalized silica nanoparticles to coat various optical elements and have measured the CA and optical transmission between 190 and 1100 nm on these elements. The functionalized silica nanoparticles were dissolved in a solution of the solvents, while the binder used was a polyurethane clearcoat. This solution was spin-coated onto a variety of test glass substrates, and following a curing period of about 30 min, these coatings exhibited superhydrophobic behavior with a static CA ≥ 160°.