Physics of Schottky Electron Sources: Theory and Optimum Operation, 1st Edition (Hardback) book cover

Physics of Schottky Electron Sources

Theory and Optimum Operation, 1st Edition

By Merijntje Bronsgeest

Jenny Stanford Publishing

266 pages | 7 Color Illus. | 168 B/W Illus.

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pub: 2014-07-25
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The Schottky electron emitter is a predominant electron-emitting source in today’s electron beam equipment. This book comprehensively covers the Schottky emitter, dealing with its theoretical as well as practical aspects. The main questions that are addressed in this book are: what is the Schottky electron emitter? How does it work? And how do its properties affect the performance of electron beam equipment?

The focus is on the direct link between the operating conditions of the source and the properties of the beam at the target level. This coupling is made clear by discussing the effect of the operating conditions and the geometry of the source and gun on the emission properties of the emitting surface, the effect of Coulomb interactions on the brightness and energy spread in the first few millimeters of the beam path, and the effect of the operating conditions and the shape of the emitter on the consequences of the beam at the target. The final chapter combines all these effects to demonstrate that there is a trade-off to be made between brightness, energy spread, and shape stability.


"Really understanding the physics of Schottky electron sources is a must for every sophisticated user of an electron microscope. But also, it is an intellectual pleasure in itself to learn about this ever-changing nanocrystal from which the electrons in the microscope emerge. The author has managed to combine these aspects, usefulness, and theoretical depth, in the elegant and clear style that characterizes her work."

Prof. Pieter Kruit, Delft University of Technology, The Netherlands

"This book describes practical aspects of using Schottky electron sources in electron optical systems on the basis of well-founded physics theory. It makes clear how the electron source performance changes with the operating parameters and why. The book is especially valuable to those who want to make the best use of this high-potential electron source."

Dr. Shin Fujita, Shimadzu Corporation, Japan

Table of Contents


Electron emission from a surface

The potential energy barrier at a surface

Emission by heating

The effect of an electric field on the potential energy barrier at a surface

Emission by heating and applying an electric field

Emission from a Schottky emitter

Work function variations across the emitter surface

Applying a bias

Applying a heating current

Total emission current

Emission from the end facet

The facet-extractor lens

The effect of the voltage settings

The effect of the emitter geometry

Schottky plots

The effect of the heating current

The final beam for applications

Imaged by the electron-optical system: the virtual source

Current in the source image: practical brightness

Total probe size: source image plus diffraction plus aberration contributions

The effect of electron-electron interactions in the beam

Summarizing: the beam properties relevant to electron optical systems

Geometrical stability

Observed geometrical changes

Equilibrium crystal shapes

Tip size growth

Changes of the end facet geometry

Collapsing of the end facet

The effect on the beam properties

Concluding remarks

Optimum operation

Maximum performance for different applications

Source monitoring tools

Practical considerations

Appendix A. Procedures for monitoring in a few commercial systems

Appendix B. Procedure to characterize system performance





Curriculum Vitae

About the Author

Merijn Bronsgeest obtained her M.Sc. cum laude in 2004 at the Materials Science & Engineering department at Delft University of Technology, the Netherlands, being honored with the award for Best MS&E Graduate of the Year. She earned her Ph.D. in applied physics cum laude from the same university in 2009 for her work on Schottky electron sources, which was a project in collaboration with FEI Company. In 2009 Merijn went to the University of Maryland to work on carbon nanotubes. In a first project, she designed and fabricated a write-one-read-many memory based on carbon nanotube transistors. After that, she focused on the characterization of thermal transport properties of carbon nanotubes with an in situ TEM technique. In 2011 she participated in a session of the Global School of Advanced Studies on graphene in Grenoble, France. This led to her moving to Grenoble in 2012 to work at CEA as a Eurotalents fellow on new two-dimensional materials.

Subject Categories

BISAC Subject Codes/Headings:
SCIENCE / Microscopes & Microscopy
SCIENCE / Physics
TECHNOLOGY & ENGINEERING / Electronics / Microelectronics