Date: Thu, 2 Jun 1994 08:30:58 +0000 (GMT)
Subject: EM/XPS : Re: Chemical shifts in x-ray spectra
From: "Keith R. Hallam"
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> Although X-ray spectra can do this sort of work, isn't it true
> that for the most part the electron spectroscopies tend to do
> the job easier? I'm thinking here of mainly of ESCA/XPS (i.e.
> the photoelectron spectroscopies).
>
> Nestor Zaluzec
> ANL EMCenter
>
It depends on the spatial resolution you require. Here in Bristol we have
a VG Escascope small area/imaging x-ray photoelectron spectrometer. The
smallest area you can obtain XPS spectra from is 50um diameter, so that is
the smallest area from which you can obtain chemical shift information (as
long as you are prepared to wait a considerable time for the spectrum to
appear out of the noise). In the imaging mode, <10um resolution can be obtained,where you image a chosen photoelectron energy, so the distribution of a particular chemical shift can be seen, at that sort of resolution. Newer instruments canimage down to 1
-2um. Nevertheless, *if* you can obtain the data you want on an
sem or probe, then maybe, and I don't really have any experience of looking for
chemical shift in wdx or edx spectra, you can more easily do so in small regionsof the sample, and perhaps with shorter acquisition times.

Keith Hallam
Interface Analysis Centre
University of Bristol
England