High Resolution X-Ray Diffractometer

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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