The heteroepitaxial growth of yttrium barium copper oxide and other metal oxides on silicon and gallium arsenide by pulsed laser deposition

Earlier attempts to produce high quality thin films of YBa{dollar}sb2{dollar}Cu{dollar}sb3{dollar}O{dollar}sb{lcub}7-delta{rcub}{dollar} (YBCO) on Si substrates were thwarted by their reactivity and thermal expansion behavior. This research has demonstrated several epitaxial buffer layer systems including yttria-stabilized zirconia and MgO which allow the epitaxial growth of YBCO on Si without chemical reaction. All of the materials may be grown in a single process by laser deposition. Pulsed laser deposition has been proven to be a rapid and versatile technique for exploring new epitaxial systems on a variety of substrates; this work has provided the first extension of pulsed laser deposition to epitaxy on semiconductor substrates. Although direct epitaxy of YBCO on silicon may not be possible, buffer layers permit the growth of device quality YBCO films with critical current densities in excess of 10{dollar}sp6{dollar} A/cm{dollar}sp2{dollar} at 77 K. Methods have been developed to pattern these films in-situ by removing the buffer layer in selected areas to produce isolated superconducting mesas. The complications of thermally induced tensile stress have been eliminated through the use of silicon-on-sapphire instead of silicon. This work has revealed methods for controlling the in-plane epitaxy of YBCO films on zirconia via homoepitaxy and nucleation-initiating monolayers. Recent research has demonstrated that some of the epitaxial growth processes developed for Si may be adapted to produce similar results on GaAs substrates.