MgB_2超导薄膜的微波测量

Microwave measurements of the MgB_2 thin film

报道了利用蓝宝石介质谐振器技术测量MgB2 超导薄膜的微波表面电阻Rs、0K时的穿透深度λ(0 )和超导能隙Δ(0 ) .λ(0 )和Δ(0 )的值是通过先测量样品穿透深度λ(T)的变化量Δλ(T) ,然后由BCS理论模型拟合Δλ(T)的实验数据得到的 .测试样品是利用化学气相沉积技术在MgO(111)基片上制备的c轴织构的MgB2 超导薄膜 ,薄膜的超导转变温度和转变宽度分别为 38K和 0 . 1K .微波测试结果表明在 10K ,18GHz下MgB2 薄膜的Rs 约为 10 0μΩ ,可以和高质量的YBCO薄膜的Rs 值相比拟 ;BCS理论拟合得到的MgB2 超导薄膜的λ(0 ) =10 2nm ,Δ(0 ) =1 .13kTc.

We have measured the microwave surface resistance R-s, the magnetic field penetration depth lambda(0) and the energy gap Delta(0) of MgB2 thin films using the dielectric resonator technique. The c-axis textured sample, with superconducting transition temperature of 38K and transition width of 0.1 K, was prepared on MgO(111) substrates by the chemical vapor deposition method. The R-s value of the MgB2 thin film at 10 K was found to be as low as 100 mu Omega, which is comparable to that of a high-quality high-temperature thin film of YBCO. BCS fits of the temperature dependence of Delta lambda of the MgB2 thin film gave lambda (0) = 102 nm and Delta(0) = 1.13 kT(c).