The overall competence of this research department is the growth of crystalline samples with extremely well-defined properties. Our work is based on molecular beam epitaxy (MBE) and is directed at two complementary tasks. On the one hand, our experimental contribution to the research of the institute is the fabrication of custom-designed nanostructured samples. On the other hand, the growth mechanisms themselves are investigated, both for their own scientific sake and in order to optimize and manipulate the sample properties in a rational way.
Epitaxy is a process in which one crystal, the adsorbate, is grown on another crystal, the substrate, in such a way that there is a unique relation between the orientations of the two crystal lattices. Typically, the adsorbate is at most a few micrometers thick. Compared to the growth of bulk crystals, epitaxy offers several advantages: First, epitaxy allows the synthesis of materials that are only metastable and cannot be grown as bulk crystals at all. Thus, materials can be grown with specific and tailored properties that could not be obtained in any other way. Second, during epitaxy the composition of the growing crystal can be changed very abruptly – on the atomic scale – so that heterostructures consisting of different materials can be fabricated. In such heterostructures quantum phenomena can be observed, and by tailoring the heterostructures quantum phenomena can be manipulated and new functionalities can be achieved. Therefore, epitaxy is a means to realize nanostructured materials as well as artificial low-dimensional semiconductor systems and to tune their mechanical, optical, electronic, and magnetic properties.