GROWTH OF THIN CEO2-YBA2CU3O7 SUPERLATTICES

We have grown a series of CeO2-YBaCu3O7 superlattices by pulsed laser deposition. The purpose was to study the growth of an insulator - high temperature superconductor system on a subnanometre scale. This is im portant for superconducting devices, since the superconducting coheren ce length is of the order of one to a few nanometres. The scale of the superlattices ranges from a period of about 10 nm down to about 3 nm. The structure of the layers was studied using X-ray diffraction and t ransmission electron microscopy. We found that superlattices have a co herent, epitaxial structure. The CeO2 follows the Frank - van Merwe gr owth mode, where the growth proceeds by growing islands about 2 nm thi ck that coalesce to form a continuous CeO2 layer at an average thickne ss of 2 nm. We see no evidence of chemical mixing between the YBa2Cu3O 7 and CeO2, which implies that they are mutually insoluble at the grow th temperature. We have characterized the superconducting properties o f the layers using a microwave cavity method at 30 GHz. If the CeO2 la yers are thin enough, the superlattices have similar surface resistanc e and critical temperature as pure YBa2Cu3O7 filMS.