Abstract The contrast from microdefects in ZnGeP2 crystals is studied. Simulation of images in X-ray topography based on the Borrmann effect is carried out for a model of a coherent inclusion of spherical form in an infinite isotropic matrix. For this simulation, a semi-phenomenological theory of contrast from defects with a slowly changing deformation field is applied. It is shown that the contrast from the inclusion is a complex function, depending on the nature of defect (sign of the deformation of the matrix), the magnitude of the deformation caused by the defect, its depth in the crystal, the modulus of the diffraction vector g and the topography used (reflection or transmission). The most common images are intensity rosettes of double or triple contrast, whose lobes are elongated along the diffraction vector. These are created by inclusions, located near the X-ray exit surface of the sample. Analysis of experimental data shows that the majority of microdefects in ZnGeP2 revealed by Borrmann method (~96%) show good agreement with proposed model. All the features of the experimental images are explained by the theory. Additionally, the contrast from dislocation loops and from groups of big inclusions which have non-Coulombic deformation fields is observed.

中文翻译：

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通过 X 射线形貌对 ZnGeP2 单晶中的微缺陷进行成像

摘要 研究了ZnGeP2晶体中微缺陷的对比。基于 Borrmann 效应的 X 射线地形图像模拟是针对无限各向同性矩阵中球形相干夹杂物的模型进行的。对于这种模拟，应用了一种半现象学理论，该理论与具有缓慢变化的变形场的缺陷形成对比。结果表明，夹杂物的对比度是一个复杂的函数，取决于缺陷的性质（基体变形的标志）、缺陷引起的变形量、其在晶体中的深度、衍射矢量 g 和使用的地形（反射或透射）。最常见的图像是具有双重或三重对比度的强度玫瑰花结，其瓣沿衍射矢量被拉长。这些是由夹杂物创造的，位于样品的 X 射线出射面附近。实验数据分析表明，Borrmann 方法揭示的 ZnGeP2 中的大多数微缺陷 (~96%) 与所提出的模型具有良好的一致性。实验图像的所有特征都由理论解释。此外，还观察到位错环和具有非库仑变形场的大包裹体组的对比。