Superconducting electronic film structures

Progress toward the fulfillment of the five main objectives of this program include the following results: V-Si and Nb-Ge films with critical temperatures of approx. 12K were reactively sputtered at deposition temperatures of < 300 deg C. NbN film with critical temperatures of 12K were magnetron ractively sputtered on 20 C substrates. Critical temperatures of > 15 K were obtained on 300 C. Solid state epitaxial growth of NbN single crystals was achieved on six different surface orientations of sapphire by annealing sputtered amorphous Nb-N. Epitaxial films of Nb, Nb-Sn, and Nb-Ge were e-beam evaporated on sapphire. A LEED study of Nb-Ir single crystals lead to an in situ procedure for producing epitaxial quality surfaces. A new UHV facility capable of e-beam evaporation and magetron sputtering of films and equipped with in situ RHEED, XPS, and Auger spectroscopy was installed and became operational. An XPS study of tunnel barrier thickness discovered large fluctuations in thickness across each juncion which appear to be a universal property of tunnel barriers. Single crystal films evaporated from ultrahigh purity Nb (< 10 ppm interstitials) were prepared for RF loss studies.