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

High-quality YBa₂Cu₃O₇ thin films were grown in situ on various substrates (SrTiO₃, Al₂ O₃, 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^-3 -10^-2 mbar. The substrate holder temperature is 700°C. The real substrate temperature is estimated to be lower than 650°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 SrTiO₃ and has a T_c.onset of 88 K and a T_c0 of 80 K. One 200-nm-thick film grown on bare silicon has a T_c.onset of 88 K and a T_c0 of 60 K. This film shows negligible superconductor-substrate interactions according to the RBS measurements