高T_cYBa_2Cu_3O_(7-x)F_y超导体表面和体相的化学态的XPS研究

The Study of the Chemical States of the Elements at the Surface and Bulk Phases of High Tc YBCOF Superconductors by XPS

以NH_4F作为F^-源,制备了一系列不同含F量的高T_cYBa_2Cu_3O(_7-x)F_v超导体,在名义F含量小于1.5mol范围内,其T_c值均比与之对照的不含F样品高2～6K.用XPS研究了这类含F材料表面和体相的化学态及其变化,根据同种化合物中不同元素间的结合能差和其它辅助实验结果,标识了每个元素不同化学态的光电子峰,并对各个峰的可能来源及其对应原子在结构中的位置和作用进行了讨论.结果揭示,表面和体相的化学态存在着较大差异.

XPS was used to study the chemical states of the elements at the surface and bulk phases of a series of high T_c YBCOF superconductors fabricated by solid state reaction of Y_2O_3, BaGO_3 or BaO_2, CuO and NH_4F as well as the changes of the surface and bulk species. The photoelectron peaks of the each element with the different chemical states at the surface and bulk phases of the superconductors were identified in terms of the binding energy differences between the two kinds of the different elements in the same compound and some of results from additional experimental works. Moreover, the possible origin of each peak and the position and function of the atom correspon ding to the peak in the superconducting structure were discussed.