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arXiv 0807.1701cond-mat.mtrl-sci
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高能光电子衍射:模型计算和未来可能性

High energy photoelectron diffraction: model calculations and future possibilities

Aimo Winkelmann, Charles S. Fadley, F. Javier Garcia de Abajo

摘要:

我们讨论的理论建模的X射线光电子衍射(XPD)与硬X射线激发在高达20千电子伏,使用电子衍射的动力学理论来说明的衍射图案的特征方面,从这样的本地化的发射源在多层晶体。我们表明,通过动态计算金刚石,硅,铁的动力学理论预测现有的数据为1千电子伏左右的较低的能量,并在约1千电子伏以上的能量模式占主导地位的菊池带,这是由动态散射的电子从晶格平面。在这样的频带的精细结构的起源进行了讨论,从原子的位置在单位细胞的角度来看。特定于元素的光电子菊池带的轮廓和位置被发现是敏感的晶格畸变(例如1%的tetraxide畸变)和杂质或掺杂剂相对于晶格位置的位置。我们还比较了动力学计算的结果,更经常用于描述低能量XPD的集群模型。我们的结论是,硬XPD(HXPD)应该能够提供独特的批量敏感的结构信息,为各种复杂的材料在未来的实验。

英文摘要:

We discuss the theoretical modelling of x-ray photoelectron diffraction (XPD) with hard x-ray excitation at up to 20 keV, using the dynamical theory of electron diffraction to illustrate the characteristic aspects of diffraction patterns resulting from such localized emission sources in a multi-layer crystal. We show via dynamical calculations for diamond, Si, and Fe that the dynamical theory well predicts available current data for lower energies around 1 keV, and that the patterns for energies above about 1 keV are dominated by Kikuchi bands which are created by the dynamical scattering of electrons from lattice planes. The origin of the fine structure in such bands is discussed from the point of view of atomic positions in the unit cell. The profiles and positions of the element-specific photoelectron Kikuchi bands are found to be sensitive to lattice distortions (e.g. a 1% tetragonal distortion) and the position of impurities or dopants with respect to lattice sites. We also compare the dynamical calculations to results from a cluster model that is more often used to describe lower-energy XPD. We conclude that hard XPD (HXPD) should be capable of providing unique bulk-sensitive structural information for a wide variety of complex materials in future experiments.

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