Microstructural studies of YB2Cu3O7-δ/Nd2CuO4/YB2Cu3O7-δ Josephson junctions with a Nd2CuO4 buffer layer grown on YSZ substrate

The effect of Nd2CuO4 (NCO) buffer layer on the microstructures of YB2Cu3O7-x/Nd2CuO4/YB2Cu3O7-x Josephson junctions grown on a YSZ substrate was investigated by high-resolution X-ray diffraction, small angle X-ray reflection, X-ray reciprocal space maps, atomic force microscopy and scanning electron microscopy. The results show that the YBCO films were well oriented in the [00L] direction perpendicular to the substrate surface. No intermediate layer was formed between the YBCO and NCO films. The FWHM of the YBCO film with a NCO buffer was smaller comparing to that of the YBCO film deposited directly onto YSZ substrates. Moreover, its surface morphology was more compact and the average size of grains on the surface was also much smaller, forming a solid base for fabrication of YBCO/NCO/YBCO multilayer Josephson junctions.