Hi Mikko,
it is interesting. You can often observe such bumps when dealing with
crystals oriented (or cutted) with some small angle off the axis (say, <5
degrees). Then this bumb is just a Bragg tail of very intensive reflection
and it can be very broad. We see this bumps in our Si crystals which cutted
along (111) with 4 degrees deviation off the axis. In common theta-2theta
scan there is a bump near 28.4 and a small sharp peak in the centre of it.
Maybe there is some misoriented blocks in your wafer?
In is easy to check for it. Just set 2Theta to this bump maximum and take a
theta scan. If there is blocks you will see them.
With best regards,
Eduard.
----- Original Message -----
From: "Mikko Heikkilä" <mikko.j.heikk...@helsinki.fi>
To: <alor...@unex.es>
Cc: <rietveld_l@ill.fr>
Sent: Friday, April 24, 2009 2:14 PM
Subject: Re: grazing angle diffraction in single-crystal Si
Hello all.
Just a comment here. I've noticed that when I measure films on Si(100)
wafer using 1° incident angle there is very often a wide bump (sometimes
superimposed with a narrow peak) at approximately 55°2theta. I'm not
quite sure from where it originates, but it usually disappears if sample
is rotated or incident angle is changed. (311) isn't too far away
though, a sharp peak should be observed at 2-3° incident angle if I've
figured it right, so maybe bump is releated to that. The point is that
although Iuliana said that one wouldn't probably see anything, I think
that on certain parameters the Si can be observed (which is sometimes a
nuisance).
I haven't spent too much time trying to figure out the origin of the
bump, though, since it usually disappears by rotating the sample and
we're dealing with polycrystalline films so rotation doesn't really
matter. Anyway, I'd be more than happy if someone here would know the
reason for this phenomenon.
Regards,
Mikko
--
Mikko Heikkilä, M.Sc.
Laboratory of Inorganic Chemistry
Department of Chemistry
P.O.Box 55 (A.I. Virtasen aukio 1)
FI-00014 University of Helsinki
