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SUMMARY:Highly spatially resolved TEM cathodoluminescence of III-Nitride b
 ased nanostructures
DTSTART:20150619T141500
DTSTAMP:20260407T105357Z
UID:5d6ec603a3ada9df8f6081339ff53958a8a7cf1553c833e2c7f5dce5
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Dr. Jürgen Christen\, Institute of Experimental Physic
 s\, Otto-von-Guericke-University Magdeburg\, Magdeburg\, Germany\nFor a de
 tailed understanding of complex semiconductor heterostructures and the phy
 sics of devices based on them\, a systematic determination and correlation
  of the structural\, chemical\, electronic\, and optical properties on a n
 anometer scale is essential. Luminescence techniques belong to the most se
 nsitive\, non-destructive methods of semiconductor research. The combinati
 on of luminescence spectroscopy – in particular at liquid He temperature
 s - with the high spatial resolution of a scanning transmission electron m
 icroscope (STEM) (dx < 1 nm at RT\, dx < 5 nm at 10 K)\, as realized by th
 e technique of low temperature scanning transmission electron microscopy c
 athodoluminescence microscopy (STEM-CL)\, provides a unique\, extremely po
 werful tool for the optical nano characterization of semiconductors\, thei
 r heterostructures as well as their interfaces.\nOur 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 col
 lected by a parabolically-shaped mirror above the sample and focused onto 
 the entrance slit of a grating monochromator. In STEM mode the electron be
 am 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 volt
 age is optimized to minimize sample damage and prevent luminescence degrad
 ation under electron\nbeam excitation.\nTypical results\, which will be pr
 esented\, include nm-scale correlation of the optical properties with the 
 crystalline real structure of GaN/AlN quantum dots. In particular\, we wil
 l show the preferential nucleation of GaN/AlN quantum dots at threading di
 slocation without inhibition of very sharp emission lines with line width 
 below 500 μeV.
LOCATION:PH L1 503 (Aquarium) http://plan.epfl.ch/?room=PHL1503
STATUS:CONFIRMED
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