Preparation of ultra-flat YBCO thin films by MOCVD layer-by-layer deposition

We propose a new growth method for YBCO thin films employing metalorganic chemical vapor deposition. In this study, the source materials were supplied in the form of a sequence including a subunit cell block. The films deposited on MgO and SrTiO3 substrates were investigated by SEM, XRD, EDX and AFM. YBCO films without precipitates, with a surface roughness of ±1 unit cell, were prepared by a sequence starting with a Ba layer then supplying a /Cu, Y, Cu/ block and ending up with a Cu—O chain layer. This result can be explained by the good wettability of Ba onto the substrates and suppression of forming impurity phases such as barium cuprates. We performed real-time optical in situ monitoring during the block deposition. Preliminary results indicate that optical monitoring is useful to monitor microscopic crystal growth of this material.