Thin Film Growth of High Tc Superconductors by Microwave Plasma Assisted Reactive Evaporation

Abstract

ABSTRACTThe oxidizing activity of an oxygen plasma is investigated in terms of the oxygen content of HoBa2Cu3Ox. thin films. The thermodynamically stable region of HoBa2Cu3Ox. and the region where the HoBa2Cu2Ox films are formed are also determined both in molecular oxygen and in an oxygen plasma. The oxidizing activity of an oxygen plasma is equivalent to that of molecular oxygen at three orders of magnitude higher pressure. The oxygen plasma expands the thermodynamic stability limit toward higher temperatures and the oxidizing activity limit toward lower oxygen pressures. In addition, the interfacial reaction between an oxide superconductor and silicon is investigated. The oxygen ions in HoBa2Cu3O film diffuse into Si even at room temperature, probably enhanced by the strong affinity of silicon for oxygen ions.