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Ultra-bright electron sources for pulsed electron microscopy

English title Ultra-bright electron sources for pulsed electron microscopy
Applicant Fontcuberta i Morral Anna
Number 176680
Funding scheme Bridge - Discovery
Research institution Laboratoire des matériaux semiconducteurs EPFL - STI - IMX - LMSC
Institution of higher education EPF Lausanne - EPFL
Main discipline Material Sciences
Start/End 01.02.2018 - 31.01.2022
Approved amount 426'963.00
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All Disciplines (2)

Material Sciences
Microelectronics. Optoelectronics

Keywords (4)

pulsed electron microscopy; cathodoluminescence; semiconductors; nanotechnology

Lay Summary (French)

Source d'électrons ultra-brillante pour la microscopie électronique pulsée
Lay summary

L’objectif de ce travail est d’obtenir les bases scientifiques et techniques pour la prochaine génération de sources d’électrons pulsées, qui devraient améliorer la technologie actuelle de plusieurs ordres de grandeur. Le succès dans ce projet permettra des grands changements dans la technique de microscopie électronique car cela permettra l’implantation de mesures en mode dynamique dans les microscopes électroniques. Ce type de mesures permettra d’étudier la réponse des matériaux résolue dans le temps mais aussi de réduire de façon significative l’exposition à une haute dose d’électrons. La technique pourra être implantée dans des chaines de production des dispositifs électroniques et optoélectroniques car elle permettra une détection rapide des défauts.

La nouvelle génération de cathodes sera basée sur la technologie GaN. Nous allons étudier la meilleure configuration des matériaux, l’optimisation de la forme de la source ainsi que sa durabilité. Nous espérons avoir un prototype de source brillante d’électrons à la fin du projet.

Direct link to Lay Summary Last update: 05.12.2017

Responsible applicant and co-applicants


Name Institute


The main objective of this project is to provide the scientific and technical basis for next generation pulsed electron sources that outperform current technology by several orders of magnitude. Success in this technology will enable the improvement of current electron-excitation microscopy and support the downsizing evolution of the semiconductor industry by enabling a new set of dynamic measurements in production sites, which are currently impossible as it evolves towards sub-20 nm nodes. It will also directly allow progress towards more efficient light emitting diodes and solar cells by enabling direct detection of defects.We are proposing a disruptive technology for pulsed electron emission, based on the photo-excitation of GaN nanostructures. Novel technical capabilities to manufacture and nanostructure GaN have arisen and consolidated over the last decade, making this project possible today. The proposed structures should provide cathodes with quantum efficiencies in the range of 2.5 to10%. Achieving these values would represent an improvement between 250 and 1000 times with respect to current tip pulsing technologies.The next generation of pulsed cathodes will be first optimized by modelling the band structure and field-effect enhancement through tip shape engineering. The cathodes will then be fabricated by top-down fabrication methods and tested in a specially designed chamber. The efficiency and durability of the cathodes will be characterized to further improve the design. Answering the following fundamental questions is paramount to the development of these cathodes:•What GaN-based heterostructure design minimizes the electron work function at the surface of the tip?•What type(s) of defect(s) are produced during the tip structuration process? Do they affect the functionality and/or durability of the cathode?•What is the emission process and does it have an activation period limiting the time resolution?•When these cathodes are integrated into an electron microscope, how does its resolution vary when the number of electrons per pulse is increased? In particular, is there a threshold after which space-charge effects make it worse?•Are the GaN-based cathodes compatible with a constant-wave laser to perform conventional electron microscopy measurements?•How does these cathodes cleanliness affect the obtained band structure, and therefore their ability to emit electrons?• What is the durability of these GaN-based cathodes in terms of stability - in other words what at their degradation mechanisms? Are there procedures to mitigate these mechanisms and improve their lifetime?