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Second Innovation Prize of the University Paris Sud for members of the LPS


The eleventh Award ceremony for innovation of the University Paris-Sud was held Thursday, November 20, 2014. M. Kociak, M. Tencé and M. Pelloux from the LPS were awarded the second prize for the project : "Nano-cathodoluminescence : Industrialization of a high performance cathodoluminescence detector dedicated to transmission electron microscopes. "

The invention relates to a system for acquiring cathodoluminescence signals, that is to say, the light emission from a material bombarded by electrons, in a Scanning Transmission Electron Microscope (STEM). Such an equipment makes it possible to obtain information both on the structure (down to less than an angström) and optical properties (at the nanometer scale) of the nano-object. This invention allows for much more precise and faster observations than existing technologies while being easy to use and maintain. LED type technologies, photovoltaic and bio-imaging are application fields of this project.


False color representation of a hyperspectral cathodoluminescence image of an AlN wire containing GaN quantum wells emitting at different wavelengths. Collaboration Tchernycheva M. & F. Julien (IEF), R. Songmuang (Institut Néel). Image courtesy of L. Zagonel (UNICAMP, Brazil).

 

With the advent of nanomaterials, it has become possible to modify and control the optical properties by structuring the matter at the scale of a few nanometer. This intimate relationship between structure and optical properties requires the development of techniques able to obtain both the structure and optical properties of the same nanoobjet. The diffraction limit usually hampers the use of far field optical techniques (optical microscopy), while the optical near-field techniques are often limited to niche applications.

The cathodoluminescence (CL) is a well known technique in the scanning electron microscopes to obtain the optical information by collecting the light emitted by a solid irradiated with a focused electron beam. However, a large number of technical and conceptual limitations restricted the use of the CL for objects with sizes roughly larger than the wavelength of visible light. These limitations relate particularly to the poor spatial resolution finally obtained (a few microns or hundreds of microns in general), the strong influence of the electron beam on diagnoses (degradation, heating, nonlinearity ...), slow acquisitions and weak signals collected when trying to get a good spectral resolution.

The solution implemented by the award-winning invention overcomes most of these limitations. This is a cathodoluminescence accessory for scanning transmission electron microscopes (STEM) fitted with a scanning electronics adapted to hyperspectral imaging. It first yielded the emission wavelengths of individual objects with sizes less than a tens of angström, and separated by a few nanometers one from the other. This nano-cathodoluminescence (nano-CL) has been since his first success in 2010 routinely used on a STEM by more than a dozen of trained people ; it has also been used for a hundred of days as a facility by researchers of all nationalities. Its unique technical characteristics, patented several times, combined with ease of use and maintenance, as well as robustness and mechanical precision allowed indeed to answer original questions in multiple scientific fields : optics of various heterostructures or new semiconductor materials, quantum nano-optics, nano-plasmonics, correlative biological imaging with potential applications fields in various fields, especially LED-type technologies, photovoltaic and bio-imaging.