スパッタリングによるMgB₂薄膜の作製と2段階アニーリング効果

抄録

We have investigated the effects of in-situ annealing on the superconducting properties of MgB₂ thin films for the purpose of obtaining a high critical temperature close to bulk value. MgB₂ thin films were fabricated by rf magnetron sputtering on a C-plane sapphire (Al₂O₃) substrate. Thin films were produced by simultaneously sputtering pure B and a Mg metal target. Sputtering deposition was followed by in-situ annealing in a high vacuum. To prevent the evaporation of Mg from the film surface, a two-step annealing process was adopted: The first step is the crystallization stage during low-temperature annealing and the next is an improvement of the film's superconducting properties by annealing at a high temperature. Utilizing the optimal annealing process, in which a thin film is first heated at 600°C for two hours and then 670°C for two hours, we have consistently obtained thin films with a zero resistivity temperature of 32 K.