Preparation and superconducting properties of double-sided Tl-2212 thin films on LaAlO₃substrates with low temperature and long time annealing

Abstract

Double-sided Tl2Ba2CaCu2O8 (Tl-2212) thin films have been prepared on lanthanum aluminate (LaAlO3) substrates by a two-step method in which Tl-free amorphous Ba2CaCu2Ox precursor films were first deposited on the substrates by pulsed laser deposition (PLD) and the subsequent thalliation, crystallization and oriented growth of the superconducting Tl-2212 films were obtained in a long-duration annealing process in argon atmosphere at temperature around 730–750 °C. The films were characterized by means of x-ray diffraction (XRD), electron simulated x-ray microanalysis in the energy dispersive mode (EDX), scanning electron microscopy (SEM) and transport measurements. The results show that the as-prepared films are predominately single phase, except for the presence of some submicron particles on the film surface. The films show epitaxial growth with c-axis perpendicular to the substrate surface, as confirmed by XRD. The full width at half maximum (FWHM) of the (0012) peak determined from the rocking curves is 0.92° and 1.21° for the two sides of a double-sided Tl-2212 film, respectively. The zero-resistance transition temperature (TC0) is 108.8 K for one side and 106.7 K for the other side of the film. The critical current density (JC) is in excess of 106 A cm−2 for both sides of the films.

Growth and characterization of 2 inch double-sided Tl2Ba2CaCu2O8thin films on LaAlO3substrates

“…The slight difference in the morphology of the two films does not affect J C , and the small amount of Tl-2223 impurity phase in the downside film also plays no important role. These results are quite impressive as compared with those previously published [19,25].…”

“…The density of the stacking faults in the upside film is higher than that in the downside film. By virtue of the very slow ramp rate during the annealing process, we did not observe any microcracks that might significantly reduce J C in these 2 inch samples [25].…”

“…The current-voltage characteristics were inductively measured by using a J C -scan measurement system (Theva Cryoscan) to investigate the spatial distribution of J C (criterion voltage 50 μV) over the whole film. The measurement principle has been detailed in our previous article [25]. The microwave surface resistances of the films were obtained by using a cylindrical sapphire resonator with a superconducting film short end.…”

“…Previously we have fabricated Tl-2212 thin films on both surfaces of 15 × 15 mm 2 LaAlO 3 substrates at a relatively low temperature (∼740 • C) by long-time annealing [25]. But the most promising applications of high-T C superconducting films are passive microwave devices that require double-sided samples with an area larger than 2 inch [26].…”

Fabrication of CeO2 buffer layers for epitaxial growth of Tl-2212 films by the in situ two-temperature process

“…Tl 2 Ba 2 CaCu 2 O 8 (Tl-2212) films have high superconducting transition temperature [1][2][3][4], high critical current density, good chemical stability, low microwave surface resistance [5]. They are particularly attractive in HTS film families for various microwave applications such as HTS filter.…”