Abstract
Excellent quality La 2-x Sr x CuO 4 epitaxial films of 0.07≤x≤0.34 in (001) and (103) orientations have been successfully grown in situ on SrTiO 3 , LaAlO 3 , and Y-stabilized ZrO 2 substrates using 90°off-axis sputtering. A record low ion channeling minimal yield χ min of 1.9% is observed for the first time, and a χ min of 3% is routinely attained. The surface exhibits a featureless morphology under high-resolution scanning electron microscope, suggesting a roughness ≤30-40 Å. Superconductivity is maximized at Sr=0.15 with a typical T c (R=0) of 35 K, a J c (4.2 K) of 1-3×10 6 A/cm 2 , and a normal state resistivity two to three times lower than single crystals. T c shows a marked reduction with thickness, and the results are interpreted on the basis of partially relieved strained-layer growth coupled with a sensitive dependence of T c on uniaxial stress.