Highly spatially resolved TEM cathodoluminescence of III-Nitride based nanostructures
Event details
| Date | 19.06.2015 |
| Hour | 14:15 |
| Speaker | Prof. Dr. Jürgen Christen, Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany |
| Location | |
| Category | Conferences - Seminars |
For a detailed understanding of complex semiconductor heterostructures and the physics of devices based on them, a systematic determination and correlation of the structural, chemical, electronic, and optical properties on a nanometer scale is essential. Luminescence techniques belong to the most sensitive, non-destructive methods of semiconductor research. The combination of luminescence spectroscopy – in particular at liquid He temperatures - with the high spatial resolution of a scanning transmission electron microscope (STEM) (dx < 1 nm at RT, dx < 5 nm at 10 K), as realized by the technique of low temperature scanning transmission electron microscopy cathodoluminescence microscopy (STEM-CL), provides a unique, extremely powerful tool for the optical nano characterization of semiconductors, their heterostructures as well as their interfaces.
Our CL-detection unit is integrated in a FEI STEM Tecnai F20 equipped with a liquid helium stage (T= 10 K / 300 K) and a light collecting mirror. The emitted CL light is collected by a parabolically-shaped mirror above the sample and focused onto the entrance slit of a grating monochromator. In STEM mode the electron beam is convergent and either kept at a single position for local spectra or scanned over the region of interest in imaging mode. Panchromatic as well as spectrally resolved CL imaging is used. The CL-intensity is collected simultaneously to the STEM signal at each pixel. The TEM acceleration voltage is optimized to minimize sample damage and prevent luminescence degradation under electron
beam excitation.
Typical results, which will be presented, include nm-scale correlation of the optical properties with the crystalline real structure of GaN/AlN quantum dots. In particular, we will show the preferential nucleation of GaN/AlN quantum dots at threading dislocation without inhibition of very sharp emission lines with line width below 500 μeV.
Our CL-detection unit is integrated in a FEI STEM Tecnai F20 equipped with a liquid helium stage (T= 10 K / 300 K) and a light collecting mirror. The emitted CL light is collected by a parabolically-shaped mirror above the sample and focused onto the entrance slit of a grating monochromator. In STEM mode the electron beam is convergent and either kept at a single position for local spectra or scanned over the region of interest in imaging mode. Panchromatic as well as spectrally resolved CL imaging is used. The CL-intensity is collected simultaneously to the STEM signal at each pixel. The TEM acceleration voltage is optimized to minimize sample damage and prevent luminescence degradation under electron
beam excitation.
Typical results, which will be presented, include nm-scale correlation of the optical properties with the crystalline real structure of GaN/AlN quantum dots. In particular, we will show the preferential nucleation of GaN/AlN quantum dots at threading dislocation without inhibition of very sharp emission lines with line width below 500 μeV.
Links
Practical information
- Informed public
- Free
Organizer
- ICMP (Arnaud Magrez and Raphaël Butté)
Contact
- Prof. Benoît Deveaud ([email protected])