Cathodoluminescence refers to the emission of light due to the interaction with free electrons with some energy. In the most classic example, luminescent materials, like direct band-gap semi-conductors, become bright by impinging high energy electron. In cathode ray tubes, a classic example, energetic electrons hit the phosphors coated screen to produce an image of the beam position. 

An interesting way of exploring the cathodoluminescence phenomena is implementing it inside an electron microscope. In the case of a Scanning Transmission Electron Microscope (STEM), an electron beam smaller than one nanometer (1,000,000 times smaller than one millimeter) can be formed and used to promote luminescence in very small regions. In this case, it is the luminescent material itself that will limit the local character of the light emission. In the case of small hetero-structures in quantum confined systems, the luminescence can be as local as about 5 nanometers. 

This webpage contains some scientific papers about cathodoluminescence performed at high spatial and high spectral resolution, using a STEM and a cold sample stage. The STEM is a VG STEM 501, equiped with high brigtness cold field emission gun. This STEM has also an EELS spectrometer and specially designed scanning module.

Scientific results using

high spatial resolution cathodoluminescence

    Results with STEM CL in nanoscale

Last Paper:

Single-Wire Light-Emitting Diodes Based on GaN Wires Containing Both Polar and Nonpolar InGaN/GaN Quantum Wells

Single-wire light-emitting diodes based on radial p–i–n multi quantum well (QW) junctions have been realized from GaN wires grown by catalyst-free metal organic vapor phase epitaxy. The Inx Ga1Àx N/GaN undoped QW system is coated over both the nonpolar lateral sidewalls and on the polar upper surface. Cathodo- and electroluminescence (EL) experiments provide evidence that the polar QWs emit in the visible spectral range at systematically lower energy than the nonpolar QWs. The EL of the polar or nonpolar QWs can be selectively activated by varying the sample temperature and current injection level. 

Reference: Applied Physics Express 5 (2012) 014101.

Authors: Gwenole Jacopin, Andre De Luna Bugallo, Pierre Lavenus, Lorenzo Rigutti, Francois H. Julien, Luiz F. Zagonel, Mathieu Kociak, Christophe Durand, Damien Salomon, Xiao Jun Chen, Joel Eymery, and Maria Tchernycheva.

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DOI: 10.1143/APEX.5.014101

Cathodoluminescence signal in diffrent regions on the wire.