Critical current density and resistivity measurements for long patterned lines in Tl2Ba2CaCu2O8 thin films

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Abstract
Epitaxial Tl2Ba2CaCu2O8 films of thickness 0.65±0.05 μm and Tc of 105±1 K were prepared on (100) LaAlO3 through a two‐step post‐deposition thallination process and patterned by standard photolithographic techniques and ion beam milling. Using the voltage per unit length criteria Ec=1.0 μV/cm, transport critical current density Jc in zero applied field for a 1.8‐m‐long, 12±1‐μm‐wide meander line separated by 8±1 μm spaces was measured to be 1.04×107 A/cm2 at 20 K, 1.82×106 A/cm2 at 80 K, and 1.02×105 A/cm2 at 100 K. The uniformity in Jc was measured for eight line segments of about 11.7 cm length, yielding variations in Jc of 1.44–3.02×106 A/cm2 at 80 K. Jc values independent of linewidth were also measured for three 0.7‐cm‐long lines with widths of 7, 27, and 52 μm. For design of electronic circuits, resistivity may be a more useful design parameter than Jc, and detailed measurements of resistivity ρ as a function of current density J were carried out. At low temperatures (T/TcJ, and Jc is well defined. At high temperatures (T/Tc≳0.7), ρ is less strongly dependent on J near Jc. At 90 K, where Jc=7.6×105 A/cm2, ρ remained less than 10−10 Ω cm (3000× less than oxygen free high conductivity copper at 90 K) even for J=1.4×106 A/cm2. The results suggest the potential for the use of patterned Tl2Ba2CaCu2O8 films in high Jc electronic applications such as chip‐to‐chip interconnects operating at temperatures below 90 K.