Charged-particle optics of field emitters

Start date

01 July 2011

End date

20 July 2012


This project forms part of research in the theory of high electric field nanoscience.

Historically, the theories of the charged-particle (CP) optics of the focused-beam microscopies (the various types of electron microscope and ion microscope), and the projection microscopies (field electron and field ion microscopy) have not been fully integrated. The modern versions of all these instruments rely upon field emission sources (either electron or ion emission). Since the behaviour of a charged particle is independent of its mass-to-charge ratio (except when space-charge is present), an opportunity exists for greater theoretical integration.

Aims and objectives

This project aims to:

  • Develop an integrated theory of the CP optics of field emitters
  • Write tutorial-type articles setting out this theory
  • Apply this theory to the operation of scanning ion microscopes based on the gas field ion source ("picoprobers"), to the issue of how to construct improved reconstruction algorithms for atom-probe tomography, and to the question of the resolving power of field electron and field microscopy for very small emitters (in particular the circumstances in which these techniques can "resolve" carbon-carbon bonds).

Tasks include:

  1. Handbook chapter on the theory of the gas field ion source [1,2], and confirmation of source-size estimate for the helium (scanning) ion microscope [3];
  2. Integrated handbook chapter on bright field electron and ion sources [4];
  3. Preliminary estimation of thermal distribution effects on the behaviour of field evaporated ions [5];
  4. Development of projection formula for possible use in APT [6] (in progress);
  5. Development of improved theory for the resolving power of field electron and field ion microscopies (in progress) (paper in preparation).

All references are outputs in the academic period 2009-2011.


  1. J. Orloff (ed), Handbook of Charged Particle Optics, 2nd Edition (CRC Press, Baton Rouge, 2009.)
  2. R.G. Forbes, "Gas Field Ionization Sources", Chapter 3 in Ref. [1].
  3. R.G. Forbes, "Prediction of probe radius for scanning ion microscopes (alternatively called picoprobers)", 52nd International Field Emission Symposium, Sydney, July 2010.
  4. R.G. Forbes, "Theory of bright field electron and field ion emission sources", accepted for publication in: P. Russell, I. Utke & S. Moshkalev (eds), Nanofabrication using Focused Ion and Electron Beams: Principles and Applications (Oxford University Press, New York, 2011/12).
  5. R.G. Forbes, "Estimation of the field evaporation (source-side) blurring radius", Workshop on New Frontiers of Atom-Probe Applications, Oxford, September 2009.
  6. R.G. Forbes, "Ion-optics-based projection formula, for possible use in atom-probe spatial reconstruction algorithms", 52nd Intern. Field Emission Symposium, Sydney, July 2010.