Author Topic: Secondary electron distributions  (Read 640 times)

Mike Matthews

  • Professor
  • ****
  • Posts: 110
Secondary electron distributions
« on: December 18, 2018, 01:47:54 am »
I’m looking for something that will allow me to model the flux of SE emitted from a sample surface as a function of position/distance from the primary beam. If it can also give the energy and/or distinguish between SE-I and SE-II that’d be even better. Can anyone suggest/recommend anything?

Probeman

  • Emeritus
  • *****
  • Posts: 1955
  • Never sleeps...
    • John Donovan
Re: Secondary electron distributions
« Reply #1 on: December 18, 2018, 12:11:33 pm »
I’m looking for something that will allow me to model the flux of SE emitted from a sample surface as a function of position/distance from the primary beam. If it can also give the energy and/or distinguish between SE-I and SE-II that’d be even better. Can anyone suggest/recommend anything?

Hi Mike,
I'm sure you've already looked at these but Penepma generates a pe-angle-el.dat and pe-anel.dat file with electron probability densities and theta and phi angles.  The Penelope documentation says:

Quote
The files pe-angle-el.dat and pe-angle-ph.dat contain angular distributions p(θ, φ)
of emerging electrons and photons, respectively. Angular distributions, p(θ), depending
only on the polar angle (i.e., integrated over φ), are written in the files pe-anel.dat
and pe-anph.dat.

I assume that is not what you're trying to model because it doesn't include distances?
john
The only stupid question is the one not asked!

Mike Matthews

  • Professor
  • ****
  • Posts: 110
Re: Secondary electron distributions
« Reply #2 on: December 18, 2018, 02:11:39 pm »
Hi John,

Yes, that would give me the total intensity but not the position information.

JonF

  • Professor
  • ****
  • Posts: 38
Re: Secondary electron distributions
« Reply #3 on: December 19, 2018, 12:56:34 am »
Hi Mike,

Not sure if these were the papers you were referencing last week, but the calculations look to be in the following two references :

Factors Affecting Contrast and Resolution in the Scanning Electron Microscope†
T. E. Evekhart , O. O. Wells  & C. W. Oatley
Pages 97-111 | Received 21 Jul 1959, Published online: 26 Apr 2007
Download citation
https://doi.org/10.1080/00207215908937191

And

Idealized spatial emission distribution of secondary electrons
Journal of Applied Physics 43, 3707 (1972); https://doi.org/10.1063/1.1661794
T. E. Everhart and M. S. Chung

Not sure what's going on with the Everhart/Evekhart - assume this is a typo from the document scanning.

JonF

  • Professor
  • ****
  • Posts: 38
Re: Secondary electron distributions
« Reply #4 on: December 19, 2018, 01:15:14 am »
It's also discussed in this paper to some extent :

H Seiler. (1983) Secondary electron emission in the scanning electron microscope. Journal of Applied Physics 54:11, R1-R18.
Online publication date: 4-Jun-1998.

They say that the primary electron beam excited SE emissions can be estimated as the square root of the squares of the sum of the beam diameter and mean SE escape depth (that works better as an equation than a sentence!).
The BSE generated SE can be estimated as a gaussian function over the BSE emitting area.

Perhaps the mean SE escape depth and BSE emitting area can be extracted from penepma or casino or something?

Ben Buse

  • Professor
  • ****
  • Posts: 414
Re: Secondary electron distributions
« Reply #5 on: December 19, 2018, 04:53:20 am »
Penepma does not consider anything with an energy of < 50eV

Also the SE behaviour varies between insulators and metals - they have different escape depths



SE attenuation length from Cazaux 2006

Ben
« Last Edit: December 19, 2018, 04:56:44 am by Ben Buse »

Probeman

  • Emeritus
  • *****
  • Posts: 1955
  • Never sleeps...
    • John Donovan
Re: Secondary electron distributions
« Reply #6 on: December 19, 2018, 06:47:44 am »
Factors Affecting Contrast and Resolution in the Scanning Electron Microscope†
T. E. Evekhart , O. O. Wells  & C. W. Oatley
Pages 97-111 | Received 21 Jul 1959, Published online: 26 Apr 2007
Download citation
https://doi.org/10.1080/00207215908937191

Not sure what's going on with the Everhart/Evekhart - assume this is a typo from the document scanning.

Hi Jon,
It must be a typo of some sort because it's definitely Everhart:

https://en.wikipedia.org/wiki/Thomas_Eugene_Everhart

I'm sure you also know that O. O. Wells was H. G. Wells' grandson:

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1431927614001731

But I did not know that he was also an underwater cave explorer!
john
The only stupid question is the one not asked!

Mike Matthews

  • Professor
  • ****
  • Posts: 110
Re: Secondary electron distributions
« Reply #7 on: December 20, 2018, 01:23:09 am »
Thanks John,

The 1972 Everhart and Chung paper looks especially useful.

Mike

Philippe Pinard

  • Post Doc
  • ***
  • Posts: 20
Re: Secondary electron distributions
« Reply #8 on: January 08, 2019, 01:59:46 am »
Hi Mike,

I did it this way in my PhD thesis:

  • Determine the position and energy of primary and BSE electrons by Monte Carlo (I used NISTMonte, but PENEPMA or Casino will work as well). In all cases you need a lot of electrons for good stats.
  • Calculate the SE yield based on Lin, Y. and Joy, D. C. A new examination of secondary electron yield data. Surf. Interface Anal. 37 (2005), pp. 895-900
  • Calculate the energy of emitted SE based on Koshikawa, T. and Shimizu, R. A Monte Carlo calculation of low-energy secondary electron emission from metals. J. Phys. D: Appl. Phys. 7 (1974), p. 1303.

Philippe