MOCVD deposited double-sided CeO2 buffer layer for YBCO superconducting film grow on R-plane Al2O3 substrate

Abstract

Double-sided CeO2/YBCO films were grown on the double-sided polishing R-plane Al2O3 substrate using MOCVD technology. The effects of deposition parameters of the MOCVD setup on the structural orientation and surface morphology of CeO2 buffer layers grown on sapphire substrates were investigated. A series of CeO2 buffer layers were prepared by varying the substrate temperature and oxygen flow rate. The results show that when the substrate temperature is lower than 750 °C and the oxygen flow rate is lower than 400 sccm, CeO2 films is grown in a mixed (00l) and (111) orientations, and when the substrate temperature is 750 °C-840 °C and the oxygen flow rate is higher than 400 sccm, the CeO2 films are grown with a single (001) orientation. When the deposition temperature was 800 °C and the oxygen flow rate was 800 sccm, the CeO2 buffer layer structure had the best orientation with double-sided ω-scan FWHM of 0.019° and 0.02°; the FWHM of double-sided Ф-scan were 1.8° and 1.7°; the RMS roughness on both sides measured by AFM were 1.28 nm. YBCO films grown on this buffer layer have good c-axis epitaxial orientation, and the test results of the pole figure show an in-plane rotation of 45° between YBCO and CeO2 lattices. Thus, the obtained YBCO film has a critical current density of 2 MA/cm2, indicating that the films can be prepared to meet the needs of microwave devices using R-plane Al2O3 substrates.