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我们发现高超导转变温度T_c(23K)的溅射Nb-Ge膜,都含有一定量的Nb_5Ge_3相,且Nb/Ge<3。对一般样品,用感应法所测的T_c都低于电阻法所测结果约1—2K,T_c≥22K的量在样品中所占的比例相对来说都比较小。对于只含A15相的薄膜,更显示出具有几个台阶宽的转变曲线,高T_c相含量很少;而对于含有A15相和一定量Nb_5Ge_3相的薄膜,感应法测量结果是一个较陡且光滑的转变曲线。电子显微镜观察呈现出Nb_5Ge_3和A15相的有趣的分布。这些结果对于我们以前提出的Nb_5Ge_3相对高T_cA15相有稳定作用的观点是一个进一步的证明。
We found that sputtered Nb-Ge films with high superconducting transition temperature T_c (23K) all contain a certain amount of Nb_5Ge_3 phase with Nb / Ge <3. For general samples, T_c measured by the inductive method is lower than the resistance measured results of about 1-2K, T_c ≥ 22K the proportion of the sample is relatively small. For the thin film containing only A15 phase, the transition curve with several step widths is shown, and the content of high Tc phase is very small. For the film containing A15 phase and a certain amount of Nb_5Ge_3 phase, the sensing method is a steeper and smoother The transition curve. Electron microscopy showed an interesting distribution of the Nb_5Ge_3 and A15 phases. These results provide a further proof of our view that we have previously proposed the stabilization of Nb_5Ge_3 relative to T_cA15.