Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 62: Nitrides: Advanced Characterization Techniques

HL 62.4: Talk

Wednesday, March 16, 2011, 16:00–16:15, POT 51

Liquid He Temperature Cathodoluminescence Spectroscopy in a Scanning Transmission Electron Microscope — •Gordon Schmidt, Barbara Bastek, Peter Veit, Frank Bertram, and Jürgen Christen — Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany

The technique of low temperature scanning transmission electron microscopy cathodoluminescence spectroscopy (STEM-CL) provides a unique and extremely powerful tool for the optical nano-characterization of semiconductors and their heterostructures and interfaces. The combination of cathodoluminescence spectroscopy – in particular at liquid He temperatures – with the high spatial resolution of a scanning transmission electron microscope (STEM) allows a spatial excitation resolution below 5 nm.

Our CL-system is integrated in a field emission (S)TEM (FEI Tecnai F20) equipped with a liquid helium stage (T=10K / 300K) and a light collecting parabolic mirror. Optimizing the excitation conditions, such as TEM acceleration voltage, is necessary to minimize sample damage and prevent luminescence degeneration. Panchromatic as well as spectrally resolved CL imaging is used. In CL-imaging mode the CL-intensity is collected simultaneously to the STEM signal – typically the dark field image signal recorded by an HAADF detector at each pixel. This enables a direct microscopic correlation of structural defects, interfaces and their influence on the luminescence. We will present results of room temperature and liquid helium temperature STEM-CL studies of thin GaN, AlInN and GaN/InGaN heterostructures.