La掺杂对磁控溅射CaB6薄膜的影响

利用直流磁控溅射的方法制备掺La和未掺La的Ca_1-xLa_xB₆ (x = 0, 0.01, 0.02, 0.03)薄膜。利用原子力显微镜对薄膜的表面形貌及厚度进行表征。掺La的薄膜的厚度约为未掺杂的两倍; La的掺杂会使薄膜的晶粒尺寸变大。利用X射线光电子能谱对薄膜表面的化学组成进行检测。薄膜中Ca/La比接近理论值, 没有检测到其它的铁磁性杂质及元素, 尤其是Fe。Ca_0.98La_0.02B₆薄膜具有最大的室温饱和磁化强度, 强度值为84.54 emu/cm³。同时薄膜的饱和磁化强度值随薄膜厚度的增加而降低。在Ca_1-xLa_xB₆薄膜中, B₆空位是薄膜磁性的主要来源, 其它类型的缺陷例如晶界等, 同样影响着薄膜磁性的大小。

Effects of La Doping on Ca B6 Thin Films Prepared by DC Magnetron Sputtering

Abstract: Both La doped and undoped Ca1-xLaxB6 (x = 0, 0.01, 0.02, 0.03) thin films were prepared by direct current magnetron sputtering method. Morphology and thickness of these films were characterized by atomic force micros-copy. Thicknesses of doped films were about twice that of the undoped films, while the grain growth of the film was much enhanced by La doping. X-ray photoelectron spectroscopy (XPS) was used for investigating the chemical com-position of film surfaces. Calculated La/Ca atomic ratios were close to the theoretical values, and there were no other ferromagnetic impurities or elements especially iron existing in films. Ca0.98La0.02B6 films exhibited the highest room temperature saturation magnetization 84.54 emu/cm3. The saturation magnetization decreased with increasing film thickness. B6 vacancies may be the main source of magnetism. Other defects such as grain boundaries also affected the magnitude of magnetism.