Martin Albrecht
Leibniz-Institut fur Kristallzuchtung, Berlin, Germany

Atomic structure of alloys, interfaces and defects in semiconductors studied by aberration-corrected transmission electron microscopy

Location: EB1 Room 1011

Friday, September 6th 2013 - 11:00 am

Analyzing the structure of crystalline material down to the atomic level is a prerequisite to understand the relation between structure and materials properties. This holds for bulk crystals as well as for nanostructures, created to realize materials with tailor-made physical properties. Atomic resolution in transmission electron microscopy in the past could only be achieved in a number of favorable cases. It required the comparison of simulated images with experimental ones and ab-initio based methods to sort out possible structural models. The successful construction of aberration corrected electron lenses paved the way for atomic resolution transmission electron microscopy. Besides the mapping of atomic positions with high accuracy, aberration corrected TEM offers the occupancy of atom sites to be determined with high sensitivity and thus opens for the first time access to the analysis of atomic defects and of short range order phenomena in alloys. The reached spatial resolutions of 0.05 nm meanwhile hits the quantum-mechanical limits. Atomic positions can be determined with accuracies in the picometer range, single oxygen vacancies in oxide layers are detectable. In my presentation I will give a brief overview on these new possibilities and present recent examples for their applications in the field of III-Nitrides and oxide semiconductors. These are the analysis of InGaN alloys down to the atomic level, oxide-nitride interfaces and the in-situ observation of small polarons in gallium oxide.

North Carolina State University