In situ preparation of superconducting Y-Ba-Cu-O thin films on bare silicon

Large scale applications of high Tc superconducting thin films in microelectronics depend strongly on the successful preparation of high quality material using convential substrates like Si or GaAs. By means of the pulsed laser deposition technique, thin Y-Ba-Cu-O films on bare single crystal silicon substrates are deposited. To overcome problems due to strong substrate-film interdiffusion and thus the formation of a highly disordered lattice, the deposition of crystalline material is mandatory. This is accomplished in our experiments using substrate temperatures as high as 700...820°C during deposition. Our films grow as single phase material with the c-axis perpendicular to the film plane. No post deposition treatment is required to obtain high critical temperatures. Our best films so far show metallic behaviour and zero resistance temperature Tc(o) 80 K. A parameter study of in situ grown thin films shows that the optimum for the deposition temperature depends on the oxygen partial pressure. Our best films grow at Ts = 780°C and p = 1 mbar as well as at Ts = 720°C and p = 0.5 mbar.