Comparative study of YBCO film growth in the cold wall type and hot wall type MOCVD processes

We made a comparative study of YBCO film growth using two different types of MOCVD reactors, i.e., the cold wall type reactor and the hot wall type reactor. In the cold wall type reactor the substrate was heated using the heat source (halogen lamps) which was located below the substrate, while in the hot wall type reactor it was using an outside resistance heater which surrounded the reaction chamber. In the cold wall reactor, the YBCO film growth had a good lattice match with the substrates at the initial deposition stage. As the film grew further, many a-axis YBCO grains were grown at the top of the film. This is attributed to poor thermal conduction to the top of the film from the heater due to the low thermal conductivity of the formed YBCO oxide. Compared to the cold wall reactor, the temperature of the hot wall chamber was easy to be controlled uniformly in the entire substrate. It led to the growth of the dense c-axis YBCO film over the entire thickness level of the film.