In situ growth of high temperature superconductor thin films with evaporation techniques using an ozone jet

High-quality YBa/sub 2/Cu/sub 3/O/sub 7/ thin films were grown in situ on various substrates (SrTiO/sub 3/, Al/sub 2/O/sub 3/, and Si) using MBE (molecular beam epitaxy) techniques and an ozone jet. The yttrium and copper are evaporated from electron-gun sources and the barium is evaporated from a Knudsen cell. All sources are controlled by a single mass spectrometer feedback system to obtain the correct fluxes at high partial ozone pressures. During deposition, the partial ozone pressure at the substrate position is estimated to be 10/sup -3/ -10/sup -2/ mbar. The substrate holder temperature is 700 degrees C. The real substrate temperature is estimated to be lower than 650 degrees C. The films are analyzed with R(T), X-ray diffraction, and RBS (Rutherford backscattering) measurements. Scanning electron microscope photographs are taken of the surface. The best film so far is grown on SrTiO/sub 3/ and has a T/sub c.onset/ of 88 K and a T/sub c0/ of 80 K. One 200-nm-thick film grown on bare silicon has a T/sub c.onset/ of 88 K and a T/sub c0/ of 60 K. This film shows negligible superconductor-substrate interactions according to the RBS measurements.