Improved Surface Crystallinity of MgO Crystal Substrate through Annealing in Oxygen Atmosphere

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Abstract
The oxygen annealing (OA) effects on MgO substrates commercially available were closely investigated. The smeared low-energy electron diffraction spot pattern and transmissionlike spot pattern of reflection high-energy electron diffraction were dramatically changed to those of almost ideal MgO crystals through OA at 1000°C. After OA, the spotty cathodeluminescence (CL) pattern disappeared almost completely, and the peak wave-length of CL spectra shifted from blue (∼400 nm) to red (∼715 nm). The 5-nm-thick epitaxial YBaCuO films grown on (100)MgO substrates with OA exhibited good superconductivity. Otherwise, superconductivity was not evident. However, the macroscopic subgrain structure seen in the X-ray topographs showed no meaningful changes between before and after OA.