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

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/Tc<0.2), ρ increased by about two orders of magnitude for a 10% increase in J, 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.

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