In situ growth and properties of single-crystalline-like La2−xSrxCuO4 epitaxial films by off-axis sputtering

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Abstract
Excellent quality La2−xSrxCuO4 epitaxial films of 0.07≤x≤0.34 in (001) and (103) orientations have been successfully grown in situ on SrTiO3, LaAlO3, and Y‐stabilized ZrO2 substrates using 90° off‐axis sputtering. A record low ion channeling minimal yield χmin of 1.9% is observed for the first time, and a χmin 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 Tc (R=0) of 35 K, a Jc (4.2 K) of 1–3×106 A/cm2, and a normal state resistivity two to three times lower than single crystals. Tc 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 Tc on uniaxial stress.