Epitaxial growth and critical current density of thin films of YBa2Cu3O7−x on LaAlO3 substrates

Abstract

Thin films of the high-temperature superconductor YBa2 Cu3 O7−x have been produced on (100) LaAlO3 substrates by coevaporation and furnace annealing. A 14-μm-wide and 400-μm-long constriction patterned on a 0.8-μm-thick film had a zero resistance transition temperature of 90 K, a transition width of 1.5 K, and a critical current density of 8×104 A cm−2 at 77 K. Although x-ray diffraction shows a definite c-axis alignment normal to the substrate plane, further analysis reveals that c-axis alignment in the substrate plane is also present. The detailed microstructural picture is revealed by transmission electron microscopy: a continuous layer, about 0.2 μm thick adjacent to the substrate, with c axis normal to the substrate plane, and the remaining top portion of the film, with the c axis in the film plane. In spite of the bilayer structure, the film remains epitaxial (the axes of the superconductor are parallel to the 〈100〉 directions of the substrate).

Copper-Oxide Superconductors

“…The film surface had to be scratched in these cases, and several methods for making electrical contacts were then studied, as discussed in section 4.3.3.I have noted, however, that it is not necessary to use water vapor during all the annealing cycle. Similar results have been found by othersI7S ,179,lSO,181,lS2 to produce superconducting thin films when wet 02 is used only at high temperatures,where the YBa 2 Cu 3 0 7 -1i is the most stable phase. In my case, a ~ = 20 minutes during the initial high temperature soak cycle is enough to completely remove the fluorine, as determined from x-ray data on samples with stoichiometry close to the 123.…”

Low-temperature structural and Raman studies on rare-earth gallates

“…For example, single-crystalline neodymium gallate is an excellent substrate material for hightemperature superconductors and doped manganese perovskite RMnO 3 films with colossal magnetoresistance. 1,2 The low mismatch between films and substrate lattice parameters and thermal expansion coefficients favors rare-earth gallate substrates. Besides, NdGaO 3 single crystals are promising substrate material for GaN film deposition.…”

Electronic, optical and thermoelectric properties of PrMO3 (M = Al, Ga, In) from first-principles calculations

“…The coupling of displacive and magnetic order parameters of PAO makes it one of the interesting solids having more than one instability. Another series of materials, REGaO 3 are popular for their use as substrates for colossal magneto resistive manganates, Sr(Pb)TiO 3 , GaN [20] as well as high-temperature cuprate superconductor films [21][22]. The latest neutron powder-diffraction studies suggest that PAO shows the following structural phase transition: from 3 Pm m to 3 R c at 1864 K (second order), from 3 R c to Imma at 210-220 K (first order), and from Imma to C2/m at 151 K (second order) [11][12].…”