Experimental determination of electron attenuation lengths in complex materials by means of epitaxial film growth: Advantages and challenges
Experimental determination of electron attenuation lengths in complex materials by means of epitaxial film growth: Advantages and challenges
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DOI：
10.1116/6.0000291
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发表时间：
2020-07-01
影响因子：
2.9
通讯作者：
Du, Yingge
中科院分区：
文献类型：
--
作者：
Chambers, Scott A.;Du, Yingge
准确的电子衰减长度是使用电子光谱方法定量表征复杂材料的关键。在这里，作者表明，从衬底单色AlK α x射线激发的芯能级和价带x射线光电子能谱的分析和测量作为膜厚度的函数，可以用来确定在外延SrTiO（3）Ge（001）薄膜的电子衰减长度。紧密晶格匹配的外延异质结是用于确定衰减长度的理想系统，只要膜以逐层方式生长，导致原子级平坦的表面，并且掩埋界面是原子级突变的。原则上，衬底峰强度的衰减速率或膜峰强度的增加速率可用于此目的。然而，作者发现，薄膜中的结构不均匀性降低了从薄膜中产生的光电子确定的电子衰减长度的准确性。一个更可靠的信息来源是来自衬底的光电子穿过薄膜。通过使用从NIST数据库中计算的电子衰减长度的能量依赖性与Ge 3d核心和Ge衍生的价带强度相结合，作者确定电子衰减长度作为动能的函数SrTiO 3。
Accurate electron attenuation lengths are of critical importance in using electron spectroscopic methods to quantitatively characterize complex materials. Here, the authors show that analysis of core-level and valence-band x-ray photoelectron spectra excited with monochromatic AlK alpha x-rays from the substrate and measured as a function of film thickness can be used to determine electron attenuation lengths in epitaxial SrTiO(3)films on Ge(001). Closely lattice-matched epitaxial heterojunctions are ideal systems for determining attenuation lengths provided the films grow in a layer-by-layer fashion, leading to atomically flat surfaces, and the buried interfaces are atomically abrupt. In principle, either the rate of attenuation of substrate peak intensities or the rate of increase of film peak intensities can be used for this purpose. However, the authors find that structural nonuniformities in the films reduce the accuracy of electron attenuation lengths determined from photoelectrons that originatewithinthe films. A more reliable source of information is found in photoelectrons from the substrate which traverse the film. By using the energy dependence of calculated electron attenuation lengths from the NIST database in combination with Ge 3d core and Ge-derived valence-band intensities, the authors determine electron attenuation length as a function of kinetic energy for SrTiO3.