Analysis of the fluoride effect on the phase-selective growth of TlBa₂Ca₂Cu₃O_9−x thin films: Phase evolution and microstructure development

Abstract

Phase-selective growth of TlBa2Ca2Cu3O9−x films is greatly enhanced by annealing chemical vapor deposition derived BaCaCuO(F) precursor films in the presence of TlF. Nucleation of superconducting phases (≥840 °C under O2) progresses in the order 2212 → 2223 → 1212 → 1223. Annealing at 855 °C results in well-defined platelet grains, a significant number of which are a-axis oriented. Residual fluoride is not detectable at any stage of the annealing process. Thin films synthesized by TlF annealing differ markedly from films processed in the presence of Tl2O3 with Tc = 103 K and Jc > 105 A/cm2 (5 K, 4.5 T).

MOCVD Growth, Micro-Structural, and Superconducting Properties of a-Axis Oriented TlBaCaCuO Thin Films

“…Metal organic chemical vapor deposition (MOCVD) has been widely applied to film deposition of TlBaCaCuO phases containing double TlO layer phases, such as Tl-2212 and Tl-2223, single TlO layer phases, such as Tl-1212, Tl-1223, and Tl-1234, and intergrowth phases . In addition, this technique has the potential advantage of being a very reliable and reproducible method for the fast production of films with high uniformity degree in both thickness and composition over large areas.…”

Ion beam studies of Tl-based superconducting films prepared from fluorides

“…The main idea in this case is the substitution of oxygen (ionic radii 1.40 Å) by fluorine (ionic radii 1.36 Å). This procedure has been applied to bulk [10,11] as well as to thin films [12,13] of Tl-based superconductors. Not all authors have tried to detect the fluorine presence [14].…”