As we know, there are different scanning modes like 2theta scan (scanning of the diffracted beam) and 2theta/omega (scanning of the incident and diffracted beam). My question is what additional information 2theta scan can provide us which 2theta/omega cannot or vice versa?
2theta/omega and theta/2 theta scans are one and same with a minute difference in implementation. Detector and sample moves in 2theta/omega scan, where as source and detector moves theta/2 theta scan.
Coming to 2 theta scan, this is also called glancing/grazing incident XRD, here X-ray incident angle is fixed (
To the best of my knowledge, in powder diffraction the theta:2theta scan (or omega:2theta, i.e. sample and detector moving coupled at different velocities) grants the proper focusing in Bragg-Brentano geometry, whereas the 2theta one (sample fixed, detector moving) is useful to perform experiments at grazing angle geometry, i.e. when the beam must maintain a fixed and small angle with respect to the sample surface.
Hi Leonardo, thanks! let me ask you a follow up question:
what are Bragg-Brentano and grazing angle geometries?
I suggest you to consult some basic texts on powder diffractometry: you can find a lot of material in the web, including lectures and tutorials. In my opinion a very good starting textbook is Pecharsky and Zavalij, Fundamentals of Powder Diffraction, Springer, 2009 (ISBN: 978-0-387-09578-3). More specifically, some useful material to answer your questions can be found (for example) at http://epswww.unm.edu/xrd/xrdbasics.pdf and at http://mrl.illinois.edu/sites/default/files/pdfs/Workshop08_X-ray_Handouts.pdf
Good work!
2theta/omega and theta/2 theta scans are one and same with a minute difference in implementation. Detector and sample moves in 2theta/omega scan, where as source and detector moves theta/2 theta scan.
Coming to 2 theta scan, this is also called glancing/grazing incident XRD, here X-ray incident angle is fixed (
I like the question because it is fundamental in nature. Let us see if we can standardize nomenclature so that we are unequivocal. Here are some suggestions firstly to Shamsul and others that want to take full advantage of the expertise available in the RG membership and maximize circulation and hence participation by the best that RG has to offer:
1. Be succinct, precise and unambiguous in your verbiage.
2. Post your XRD data if available for us to examine.
3. You may now add/drop up to 15 topics "up top" instead of just 5.
4. Share the question with others:
i. With followers
ii. Publicly
iii. On LinkedIn and other media as provided in the "Share" button "up top"
iv. With others directly who have contributed meaningfully in other XRD based discussions on RG. You'll have to review other discussions and find them.
5. Current stats for this query includes 4 contributors, 7 followers and
- 1 / 0 • 5 Answers • 1208 Views @ 07:00 hrs. EST 06-04-2014.
6. Review basic XRD texts to get familiar with the nomenclature and conventional use of terminology by the XRD community. I'd include Compton & Allison among the texts.
Let us observe the stats after implementing these suggestions as I intend to. I have plenty to add with real time live examples for your review and convenience. Let's have some fun learning! :-)
https://www.flickr.com/photos/85210325@N04/10659886546/
Comparing "2theta scan (scanning of the diffracted beam) and 2theta/omega (scanning of the incident and diffracted beam)", de-coupled and coupled XRD rocking curve scans respectively is probably what you mean. In practice we use "Omega only" or "Omega-2Theta scan". We find no difference in information obtainable from these two methods. The advantage of the Omega-2Theta scan is that the topograph (XRD signal) remained at the same location on the detector. Meaning, the diffraction vector remains unaltered.
Here is an example of both "Omega only" and "Omega-2Theta scan" for an InAs/InAsSb superlattice epi 25nm period 10 periods (0.5um) on (001) GaSb substrate: https://www.flickr.com/photos/85210325@N04/7811469858/in/set-72157632728949610/lightbox/
Based on our observations we conclude the same as K. V. L. V. Narayanachari, no difference fundamentally!
Bragg-Bento (focusing geometry): https://www.google.com/search?q=bragg+brentano+geometry+xrd&tbm=isch&tbo=u&source=univ&sa=X&ei=cRPiU9-HOcSGyASs-ICwBQ&sqi=2&ved=0CCsQsAQ&biw=1366&bih=651
Grazing incidence angle for shallow surface layer examination:
https://www.flickr.com/photos/85210325@N04/8207353860/in/set-72157632724094863
- Badges
- Science method
- Similar topics
- Methodology
- Crystallography
- X-ray Diffraction