High Resolution X-Ray Diffractometer

申请的衍射仪将主要用于薄膜系统和半导体异质结构的高分辨率X射线衍射，这些系统和半导体异质结构是在申请人（D.罗伊特，D. J. As教授和C. Meier）。关于材料，焦点在于不同的半导体，例如GaAs/（Al，Ga）As、立方GaN/（Al，Ga）N和ZnO/（Zn，Mg）O。对于最高质量的异质结构的生长，材料的结构表征是至关重要的。分子束外延是一种复杂的方法，其中许多实验参数，如衬底温度、单个元素的分子通量、在某些情况下的气体通量和等离子体功率、样品保持器内的残余气体压力和热传导等等，决定了所制造的异质结构的质量。为了实现生长层的最佳质量，必须进行仔细的结构表征-在理想情况下，在生长后立即进行。这种结构表征不仅解决了异质结构本身X射线衍射在半导体异质结构领域的核心应用是高分辨率X射线衍射的经典方法，特别是研究应变和弛豫的倒易空间图，赝晶生长以及超晶格和界面。由于与在申请人的组中产生的大量样品相关的倒易空间图测量的高需求，测量时间的有效使用是重要的，这就是为什么系统应该允许测量过程的自动调节和自动化。此外，X射线反射计（XRR）和掠入射衍射（GID）也可用于研究最薄的薄膜，另一个应用领域是研究用不同光刻方法制造的纳米材料（AG J. Lindner）。对于这些异质结构的分析，将采用布拉格-布伦塔诺几何中的经典粉末衍射法

The applied-for diffractometer will mainly be employed for high resolution X-ray diffraction of thin film systems and semiconductor heterostructures, which are fabricated in the groups of the applicants (Prof. Dr. D. Reuter, Prof. Dr. D.J. As und Prof. Dr. C. Meier) via molecular beam epitaxy. Concerning the materials, the focus is on different semiconductors, for example GaAs/(Al,Ga)As, cubic GaN/(Al,Ga)N and ZnO/(Zn,Mg)O. For the growth of highest quality heterostructures, the structural characterization of the materials is of paramount importance. Molecular beam epitaxy is a complex method, where numerous experimental parameters, as substrate temperature, molecular fluxes of individual elements, in some cases gas fluxes and plasma power, residual gas pressure and thermal conduction within the sample holder and many more, determine the quality of the fabricated heterostructures. To achieve the optimum quality of the grown layers, a careful structural characterization has to be performed - in an ideal case directly after growth. This structural characterization addresses not only the heterostructure itself (stoichiometry and layer thicknesses as well as roughness) but also the presence of defects and unwanted three-dimensional or polycrystalline growth.Core applications for X-ray diffraction in the area of semiconductor heterostructures are classical methods of high-resolution X-ray diffraction and especially reciprocal space maps to investigate strain and relaxation, pseudomorphic growth as well as superlattices and interfaces. Due to the high demand of reciprocal space map measurements related to the high number of samples produced in the groups of the applicants an effective use of the measurement time is important, why the system should allow for auto-adjustment and automatization of measurement processes. In addition, X-ray reflectometry (XRR) and diffraction under grazing incidence (GID) should be possible for the investigation of thinnest films.Another application area is the investigation of nanomaterials fabricated with different lithography methods (AG J. Lindner). For the analysis of those heterostructure, the methods of classical powder diffractometry in Bragg-Brentano geometry will be employed