The transmission electron microscopy investigation and electrical properties of epitaxial Tl-1223 and Bi-substituted Tl-1223 thin films grown by in-situ laser ablation

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

“…Holstein et al observed a similar chemical interaction between Tl(2212) thin films and SrTiO 3 substrates [115]; however, in a crosssectional TEM study of TBCCO films grown on SrTiO 3 substrates, Morosin et al [116] found no evidence of chemical interaction even though thalliation took place in air at 850 • C. There is thus no current consensus on the reactivity of this interface at high processing temperatures. Less surprisingly, no interaction has been observed between Tl(1223) thin films grown by in situ techniques and SrTiO 3 substrates [91,114] and this is attributed to the lower deposition temperatures (between 650 and 720 • C). The use of low-temperature thalliation anneals also appears to overcome the problem of chemical interaction between TBCCO thin films and SrTiO 3 substrates [117].…”

“…This procedure has been used to grow c-axis-aligned films of Tl(1223) on both LaAlO 3 and SrTiO 3 substrates, with T c values up to 95 K on LaAlO 3 and 105 K on SrTiO 3 . The same method has been used to fabricate Bi-substituted Tl(1223) films with values of T c up to 114 K, J c (77 K) up to 8 × 10 5 A cm −2 and R s (10 GHz, 80 K) values less than 1 m [91]. Transmission electron microscopy (TEM) studies of cross-sections of both types of film [91] have shown that the films grown without Bi contained a very high concentration of defects such as a-axis-oriented grains and stacking faults.…”

“…The same method has been used to fabricate Bi-substituted Tl(1223) films with values of T c up to 114 K, J c (77 K) up to 8 × 10 5 A cm −2 and R s (10 GHz, 80 K) values less than 1 m [91]. Transmission electron microscopy (TEM) studies of cross-sections of both types of film [91] have shown that the films grown without Bi contained a very high concentration of defects such as a-axis-oriented grains and stacking faults. The Bi-substituted films contained a defected region within 150 nm of the substrate with the remainder of the film thickness being considerably more perfect.…”

“…One general point is that oxide films have a tendency for textured growth due to their strong directional bonding. Like all cuprate superconductors, the slow growth direction in TBCCO compounds is along the c-axis, while the aand b-axes are the fast growth directions [91][92][93][94]. Thus, for kinetic reasons these materials will intrinsically adopt a plate-like morphology, and the use of a substrate with a reasonable lattice match to the a-b plane of the TBCCO unit cell encourages the film to nucleate and grow with its c-axis perpendicular to the interface plane.…”

Fabrication, Structure and Properties of Tl-Based HTS Thin Films

“…A microstructural study has also been made of in-situ Tl-1223 films produced by the Regensburg group [27]. These films, grown on both SrTi03 and LaAl03 substrates, have very smooth, mirror-like surfaces, but carry no detectable supercurrent at 77K.…”