Re: Explaining for broadening of peaks due to a shift of theta in theta-two theta scanning?

[Reinhard Kleeberg]

Such an offset of the theta (omega) axis violates the para-focusing 
condition of the Bragg-Brentano geometry. You will get diffracted 
intensity from positions far below and above the gonimeter axis, i.e. 
far outside the focusing circle. The only option to reduce this effect 
is a reduction of the divergence of the primary beam. Without parallel 
beam optics, you can just reduce the opening of the equatorial slit, of 
course causing significant loss of intensity.
Reinhard Kleeberg

Huy LE-QUOC schrieb:
Dear Rietvelders,

To avoid the gigantic peaks of Si substrate (which are too dominant 
over peaks of phases in investigation on a thin film of 3 micron), we 
have tried to take a scan theta-two theta with a shift of 3 degree for 
theta (i.e. instead of theta-2theta corresponding to 5-10 degree at 
the beginning, I have set theta=8 degree and 2theta=10). In fact, we 
have been able to reduce dramatically intensity of Si peaks but the 
broadening of all peaks in the diffractogram is increased comparing to 
the "normal" scan without shift of theta.
We have also tried to rotate the sample around its perpendicular axis 
(angle Phi) to find the appropriate Phi where the peaks of Si are 
slightly decreased and found that the broadening of peaks is the same 
as in a "normal" theta-2theta scan.

Does anyone have any ideas about this increased broadening of peaks 
during a theta-2theta scan with theta shifted ?

By the way, do you know others ways, besides the razing incidence, to 
avoid the dominant peaks of substrate over the thin film  ?

Thanks a lot in advance for your any helps.

Best regards,

---
Huy LE-QUOC,
Doctorant
LPSC/UJF-Grenoble INP-CNRS, Centre de Recherche 
Plasmas-Matériaux-Nanostructures
Institut Néel/CNRS, Département "Matière Condensée, Matériaux et 
Fonctions"
53 rue des Martyrs, Grenoble 38026, FRANCE
Phone: +33 4 76 28 40 38
Fax:   +33 4 76 28 40 11