Ozone-assisted molecular beam epitaxy (MBE) has been developed for growing high-Tc superconducting films. It involves the co-evaporation of their elemental constituents together with the use of ozone as a source of reactive oxygen. The advantage of using ozone over other forms of reactive oxygen is that it is stable enough to be prepared and delivered to the substrate in a very pure form using very simple apparatus, providing a well-characterized flow of oxidizing gas. Using ozone, a post-deposition anneal is not needed to produce films with high transition temperatures, and growth can be carried out at relatively low system pressures. As a consequence, the surface analysis using reflection high energy electron diffraction is possible during film growth. Recent refinements of ozone-assisted MBE directed at the YBa2Cu3O7-σ family of films are described here. The results indicate that this technique is very competitive for growing the highest quality superconducting films and should be ideal for fabricating structures.
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The authors would like to thank J. N. Eckstein and R, W. Barton for useful discussiona nd N. Israeloff for carrying out the critical current studies. D. D. Berkley and M. L. Mecartneyc ontributedto the early stageso f this work which was supported in part by the US Air Force Office of Scientific Research under Grant AFOSR-87-0372, by the Materials Research Groups program of the National Science Foundation under Grant NSF/DMR-8908094 and by the Departmento f Administrationo f the State of Minnesota.