Al films as buffer layers for high-temperature superconducting thin films on amorphous substrates
We have prepared c-axis oriented YBa/sub 2/Cu/sub 3/O/sub 7-y/ (YBCO) thin films on amorphous substrates, such as SiO/sub 2/ and soda potassium glass, by using Al(111) buffer layer. Before preparation of YBCO film, Al surface was oxidized at a substrate temperature of 590/spl deg/C under (O/sub 2/+O/sub 3/;8%) atmosphere of 1 mTorr. This AlO/sub x/ was in an amorphous state according to X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) measurements. YBCO films were formed on amorphous substrates with the AlO/sub x//Al layer using an ArF excimer laser deposition technique. The vacuum pressure and substrate temperature during deposition were typically 1 mTorr and 590/spl deg/C, respectively. XRD measurements indicate that all the YBCO films were predominantly oriented with the c-axis normal to the substrate surface. These results show that the AlO/sub x/ plays a role of buffer and seed layer which has periodic potential of atomic order corresponding to Al(111) plane. Critical temperature T/sub c(zero)/ of the c-axis oriented YBCO film on AlO/sub x//Al/glass substrate was 75 K. This technique can be applied to other oxide material such as ferroelectric and ferromagnetic materials and is very useful for applications.