We have investigated the excitonic properties of highly crystalline ZnO hexagonal microdisks grown by the chemical vapour deposition technique. It was observed that a suitable negative catalyst like chlorine suppresses the crystal growth along the (0001) direction. We propose a qualitative model for the experimentally observed layer-by-layer growth mechanism of the microdisks. Room temperature photoluminescence of the microdisks manifests a very high near-band-edge (NBE) emission peak in the UV region and a minor defect peak in the visible region. The excitonic emission of the microdisks was studied using the low-temperature photoluminescence down to 83 K, which reveals a surface exciton peak in the NBE region and well fitted higher-order phonon replicas.
An approach to fabricate double-sided, high-current RE-Ba2Cu3O7-δ(REBCO) tapes for use in ultrahigh-field superconducting magnets operating at and above 20 T is demonstrated. In this work, we modified our advanced metal organic chemical vapor deposition (A-MOCVD) reactor to deposit REBCO films on each side of a double-sided buffer substrate in a single pass. The composition, thickness and critical current (Ic) of 1-µm-thick REBCO films on each side of the double-sided tapes are compared. Double-sided REBCO tape with 2-µm-thick films on each side showed self-field critical current density (Jc) over 2.6 MA/cm2 at 77 K and 0 T. 15%-Zr-added double-sided REBCO tape showed Ic over 530 A/4mm at 20 K, 20 T.
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