Single crystal

About: Single crystal is a research topic. Over the lifetime, 59617 publications have been published within this topic receiving 870828 citations.

Systematic enhancement of in-field critical current density with rare-earth ion size variance in superconducting rare-earth barium cuprate films

Abstract: Enhanced in-field critical current densities (Jc’s) have been obtained in epitaxial superconducting (RE1,RE2)Ba2Cu3O7−x (RE1=rare‐earthion 1, and RE2=rare earth ion 2) films grown on both single crystal and buffered metallic substrates. For a constant average RE ionic radius (equal to that of yttrium), there is a systematic dependence of the in-field Jc on the RE ion size variance, with a small, but nonzero, variance being optimum. Compared to the standard YBa2Cu3O7−x composition, a factor of two improvement in Jc(75.5K) is reproducibly observed at 0.2T(‖c) for the composition Dy1∕3Ho2∕3Ba2Cu3O7−x on both single crystal and buffered-metallic substrates. Angular dependent magnetic field studies and transmission electron microscopy indicate the presence of additional pointlike random defects.

Single crystal functional oxides on silicon

Abstract: Single-crystalline thin films of complex oxides show a rich variety of functional properties such as ferroelectricity, piezoelectricity, ferro and antiferromagnetism and so on that have the potential for completely new electronic applications. Direct synthesis of such oxides on silicon remains challenging because of the fundamental crystal chemistry and mechanical incompatibility of dissimilar interfaces. Here we report integration of thin (down to one unit cell) single crystalline, complex oxide films onto silicon substrates, by epitaxial transfer at room temperature. In a field-effect transistor using a transferred lead zirconate titanate layer as the gate insulator, we demonstrate direct reversible control of the semiconductor channel charge with polarization state. These results represent the realization of long pursued but yet to be demonstrated single-crystal functional oxides on-demand on silicon.

Fabrication of DAST Channel Optical Waveguides

Abstract: In order to use the large, electro-optic coefficient of a nonlinear optical ionic crystal, 4-(p-dimethylaminostyryl)-1-methylpyridinium tosylate (DAST), a channel optical waveguide structure is needed. We successfully fabricated a waveguide using two methods: by a dry-etching technique and by photo-bleaching. Because DAST has a large optical loss, parts of the waveguide should be composed of a transparent polymer. We used photolithography and a reactive ion etching method to fabricate a serially grafted (conjunct) waveguide of DAST with a transparent polymer waveguide. The waveguide was also fabricated by photobleaching, whereby the refractive indices of the crystal’s a- and b-axes were decreased by degrading the crystal. The cladding part of the DAST waveguide was photobleached by irradiating with UV light. The under- and over-cladding layers of these channel waveguides were composed of a UV-cured resin that did not dissolve the DAST crystal. The loss of the crystal waveguide for the crystal b-direction was around 10 dB/cm, due to the scattering loss of the DAST single crystal.

Electrical Resistivity of Thin Single‐Crystal Gold Films

Abstract: Resistivities of evaporated or sputtered polycrystalline and epitaxially grown single‐crystal gold films of thickness 100–1000 A have been measured in situ during deposition. Single‐crystal gold films have been grown epitaxially on cleaved mica by sputtering and, as indicated by electron diffraction studies, are atomically smooth over large areas. The resistivities of such films are very close to the bulk value for all thicknesses greater than a limiting thickness at which the film becomes continuous. Since the limiting thickness is appreciably lower than the mean free path for conduction electrons, this result is considered to be a consequence of the existence of specular (elastic) reflection of electrons from the film surface. Resistivities of polycrystalline films of thicknesses comparable to the electron mean free path are higher than the bulk value; and, for films grown on cold substrates, their dependence on thickness is in qualitative agreement with the theory of diffuse (inelastic) scattering of conduction electrons from the surface. For polycrystalline films deposited on heated substrates, the measured resistivity appears to be dominated chiefly by structural changes occurring during growth.