Characterization of a radio frequency plasma source for molecular beam epitaxial growth of high-7_c superconductor films

The growth of superconducting oxides in vacuum conditions compatible with molecular beam epitaxy (MBE) requires a form of activated oxygen. The activated oxygen species can be either atomic oxygen (O) or ozone (03). Here we characterize a rf plasma source by measuring the oxidation rate of a silver film on a quartz crystal deposition monitor as a function of the oxygen flow. The initial oxidation rate provides a lower limit for the actual atomic oxygen flux. If the frequency change of the quartz signal is entirely due to the oxidation of silver by atomic oxygen and we assume a detection efficiency of one, then the total cracking efficiency of the source is. estimated to be around 30%. The source was used in a MBE machine to deposit thin (200 A) high-rcfilms of DyBa2Cu307 on SrTiQ3with a 7nsetof 88 K and a rfr0of 86 K. © 1992, American Vacuum Society. All rights reserved.