NanOp - Members: Humboldt-Universität zu Berlin

Members of NanOp

HUMBOLDT UNIVERSITÄT ZU BERLIN, Berlin
Institut für Physik, Prof. Dr. W. Neumann

The correlation between crystal structure and properties, including the nano-chemistry (chemical composition and bonding), of optoelectronic devices are elucidated using

transmission electron microscopy (TEM)
high-resolution transmission electron microscopy (HRTEM)
micro-analytical technique of energy-dispersive X-ray spectroscopy (EDXS)
electron energy loss spectroscopy (EELS)
micro-diffraction and nano-diffraction techniques such as convergent beam electron diffraction (CBED)

The group is equipped with a Hitachi H8110 TEM/STEM (2.3 Å point resolution), an EDXS system Kevex Delta III and imaging energy filter GIF (Gatan), and three systems for ion-beam milling.

Dedicated specialized techniques are used to image the element distribution along a line (EDXS profile, series of EEL spectra) or two-dimensionally (X-ray mapping, energy-filtered TEM) at a lateral resolution of a few nanometers (EDXS) or even on the sub-nm scale. The chemical bonding of the elements present in the transmitted volume is characterized by analyzing electron energy loss near edge structures (ELNES). This additional information is provided by the relatively high energy resolution of the EELS technique. Even a chemical-bond mapping can be carried out, i.e. spatial differences in the fine structures are used to image the chemical-bond state either along a line or in the energy-filtered TEM image.