论文部分内容阅读
几个月前 Kellogg Melmed 观察到了 YBa_2Cu_3O_(7-x)的场离子显微镜(FIM)的原子像。88年4月我们得到了Bi_2Sr_2CaCu_2O_(8+a)的FIM原子图象。J.M.Tarascon 给出 Bi_2Sr_2CaCu_2O_(8+a)的正交晶体结构模型见图1,其中c=30.6(?)。Bi-Sr-Ca-Cu-O系分高温110k和低温80k两超导相,我们能用样品由北大物理系冯孙齐组提供,Tc～90k,基本属低温相。由北大物理系许胜勇制成FIM的针尖试样(Tip)。对FIM用完后的TiP作电镜分析表明Tip是超导体,且Tip的指向和C轴垂直,形貌见图2。FIM初真空达5×10~(-9)t,成像气为Ne或Ar。已观察的三个Tip的原子像中,重复看到等间距链状像点、平行四边形网格状像点,见图3(A)图3(B)显见互相平行的五条双层亮点区夹四条几乎不成像黑区,亮点条纹间距约为15A,宽约为3—6A。
Kellogg Melmed observed the atomic image of a field ion microscope (FIM) of YBa_2Cu_3O_ (7-x) a few months ago. In April 1988, we obtained the FIM atomic image of Bi_2Sr_2CaCu_2O_ (8 + a). J.M.Tarascon gives the orthogonal crystal structure model of Bi_2Sr_2CaCu_2O_ (8 + a) shown in Figure 1, where c = 30.6 (?). Bi-Sr-Ca-Cu-O is divided into two superconducting phases, high temperature 110k and low temperature 80k. We can use the sample provided by Fengsun Qi group of Peking University Department of Physics, Tc ~ 90k, which is basically a low temperature phase. From the Peking University Department of Physics Xu Shengyong made FIM tip sample (Tip). Electron microscopy of the TiP after the FIM was used showed that Tip is a superconductor and Tip is perpendicular to the C-axis. The initial vacuum of FIM reaches 5 × 10 ~ (-9) t, and the imaging gas is Ne or Ar. In the three observed atomic images of Tip, the equally spaced chain-like dots and parallelogram-shaped grid-like dots are repeatedly seen. As shown in Fig. 3 (A) and Fig. 3 (B), five double- Four barely image black, bright stripes spacing of about 15A, a width of about 3-6A.