Preparation of TlBa2Ca2Cu3O9±δ high T c thin films by laser ablation in combination with thermal evaporation of thallium oxide

Abstract

TlBa2Ca2Cu3O9±δ high Tc thin films were prepared on MgO 〈100〉 surfaces by a combination of laser ablation from a stoichiometric Ba2Ca2Cu3Ox target and the thermal evaporation of thallium oxide. X-ray diffraction measurements showed that the films consisted of predominantly c axis oriented TlBa2Ca2Cu3O9±δ, and scanning electron microscopy revealed that the surfaces had a flat, platelike morphology. The ac inductive measurements indicated that the onset of superconductivity occurred at 117 K with a transition width (10%–90%) of ∼3 K. Zero resistivity was reached at 120 K. The critical current density was ∼3×104 A/cm2 at 110 K.

Thallium-based HTS thin films, processing, properties and applications

“…Most routine TBCCO film fabrication is carried out by a two-step process involving the deposition of an amorphous precursor film (which may or may not contain thallium), using one of the standard thin-film deposition techniques, followed by an ex situ thalliation anneal in the presence of thallous oxide vapour to form the crystalline superconducting material. In situ growth of TBCCO films with properties comparable with those of films fabricated by ex situ methods has only been reported by a small number of groups [27][28][29][30][31][32][33][34][35][36]. In this section, the various in situ and ex situ film fabrication processes are described, and the influence of various thermodynamic and kinetic factors on the phases formed is briefly discussed.…”

“…The first successful quasi-in situ TBCCO film fabrication technique was reported by Betz et al [31] and was a two-stage process consisting of the deposition of a BCCO precursor film followed by an in situ heat treatment in the presence of Tl 2 O vapour. An improvement to this process [32] gave direct control over the vapour pressure of Tl 2 O and led to the growth of c-axis-aligned Tl(1223) films on (001) MgO substrates with T c values up to 120 K and J c values up to 1.3 × 10 5 A cm −2 at 77 K. Face and Nestlerode used off-axis magnetron sputtering in the presence of Tl 2 O vapour to fabricate Tl(1212) thin films on LaAlO 3 , NdGaO 3 and CeO 2 -buffered sapphire substrates [33,34]. To achieve the best superconducting properties (T c = 97 K) a subsequent anneal in O 2 and Tl 2 O vapour was necessary.…”

In situ preparation of epitaxial TlBa2Ca2Cu3O9 high-T c thin films

“…In a first step a polycrystalline ͑Tl͒BaCaCuO precursor film, either thallium free or containing thallium, was deposited by several methods such as sputtering, 2 laser ablation, [3][4][5] or spray pyrolysis. 6 In a second step thallium was introduced into the precursor film by a heat treatment in the presence of O 2 and Tl 2 O vapor for forming of the Tl-1223 phase.…”

A Search for a Low Anisotropic Superconductor

“…Among the thallium-based compounds the thin films of single TlO layer materials (Tl-1223) are superior because of their higher T c (0) and J c [107]. Thin films of Tl-1223 superconductors have critical current density in the range of 10 5 -10 6 A/cm 2 at 77K (both in field cooled and zero field cooled samples) depending upon the deposition technique adopted [47,66,84,[107][108][109].…”