Buffer layers for the high-Tc superconductors

The development of thin films of high critical temperature (Tc) superconductors is briefly outlined and the uses of buffer layers explored. The properties desired in a buffer are considered. Buffers for use with each of three important substrate classes are then studied: low dielectric constant substrates (principally sapphire); semiconductor substrates (especially silicon, including silicon-on-sapphire); and metal substrates. Finally, applications of buffer layers beyond that of facilitating superior superconducting films are noted. (orig.)