The relative effect on the oxygen concentration in YBa2Cu3O7−δ of atomic and ionic oxygen fluxes, produced by a small compact electron cyclotron resonance source

Abstract

The relative effect of atomic and ionic oxygen for the oxidation of YBa2Cu3O7−δ thin films is investigated. To this goal, the characteristics of an oxygen plasma produced by a small, compact, permanent magnet electron cyclotron resonance plasma source were investigated as a function of a bias applied to the plasma. With no bias, a plasma potential of 23 eV was measured by an energy analysis of the ions. With increasing positive plasma bias voltage, the ion current decreases and its energy increases above the 23 eV by the amount of applied bias voltage. When a negative voltage is applied to the plasma, both electron and ion current drastically decrease, while the atomic flux remains high. The atomic oxygen flux was measured by the oxidation rate of Ag and the etching rate of a standard photoresist as a function of distance from the source and the bias voltage. We find that the resistivity of a YBa2Cu3O7−δ film in the plasma is well characterized by the flux of atomic oxygen and that there is no significant effect of oxygen ions.