Hi Jenny,
I just wanted to add a bit to Matt's answer on TEY vs FY and suggest a
couple of reference for you.
There are three contributions to the TEY: photoelectrons, Auger
Electrons, and secondary electrons. The secondary electrons will
typically determine the maximum depth that you can observe in a TEY
measurement. There is a good description of this in Jo Stohr's book,
NEXAFS Spectroscopy which can be seen at google books.
http://tiny.cc/44VGq
There is also a quick synopsis of the book at:
http://www-ssrl.slac.stanford.edu/stohr/nexafs.htm
At this site, there is a photoelectron spectrum showing the relative
intensity of Auger and Photopeaks. The secondaries are roughly a
factor of 100 more intense than the other contributions.
It is possible to measure both TEY and Auger electron yield (AEY) and
you will see that the AEY is more surface sensitive that TEY.
Measuring AEY requires an analyzer capable of discriminating the
electron energy. AEY is typically performed at lower photon energies
as there are not too many electron energy analyzers at hard x-ray
facilities.
It is actually pretty difficult to try to calculate the maximum
analysis depth for TEY because of the three different contributions.
Here is an attempt to understand the probe depth of TEY but neglects
secondary electrons: http://www.icdd.com/resources/axa/vol44/v44_058.pdf
For the K-edges in the hard x-ray regime, with TEY it would not be
unrealistic to expect probe depths on the order of 1000 angstroms (100
nm).
Jeff
On Feb 20, 2008, at 6:33 PM, Jenny Cai wrote:
Hi all,
Could someone please answer my questions? I would really appreciate
your help.
1. For linear combination fitting, there are three indicators for
the goodness of fitting: R-factor, chi-square and reduced chi-
square. Could anyone tell me how they work?
2. Since TEY is sensitive for the surface and FY for the bulk (and
surface?), species detected by TEY should be also detected by FY,
right?
3. How to calculate the maximum analysis depths for TEY and FY?
Thank you in advance.
Jenny Cai
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