Allen J. Hall

Materials Science & Engineering, Productivity, and Life

Doctoral Studies

My New Nanostructured CI(G)S Light-Absorbing Thin Films Published in JAP

pillars For a while now I’ve been dying to share some of the new nanostructures I’ve discovered during ion-assisted vapor deposition of CI(G)S thin films. My paper was published in the Journal of Applied Physics last fall (sorry for the blog outage over the winter-break).  The paper is titled: “Nanostructured light-absorbing crystalline CuIn(1–x)GaxSe2 thin films grown through high flux, low energy ion irradiation;”  There are a lot of unanswered questions about the work that leaves me dreaming up different solutions to how these films are growing. Read More »

Finally- Qspace mapping success!

I have no idea why this took so long, but I finally have the code to import and output various graphs of the reciprocal space maps (RLM or Q-space) taken using the Xpert Xray diffraction system. One of the difficulties in outputting the older data has been solved by our new line-scan detector system. The data is now taken in the more simple Omega-2Theta space instead of Omega-Omega2Theta space. With the help of Mauro Sardela, the fantastic research scientist who runs the XRD lab at the Materials Research Laboratory (FS-MRL), I’ve properly translated the data into Q-space using the same equations the Xpert Epitaxy software uses.
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More on XRD Q-space mapping.

After some new scans, it appears the XRDMLread.m function I talked about is doing a pretty good job of getting the 2-axis scans into MATLAB. I was able to alter the code to accept the standard Epitaxy software’s translation to Q-space. (In Epitaxy the default is R = 0.5 I believe.) So, the following image was imported with XRDMLread.m the plotted with the standard 2-d example from the author’s website. The code was altered to output 10000xRLU units the same as Epitaxy (Panalytical). I haven’t checked all the numbers, but it’s looking ok so far. Unfortunately the color-scale looses it’s meaning as far as intensity is concerned, it appears at first glance.

(115) Qspace map

Working a bit with my old q-space map code, I’m able to accomplish the following:




Note the strange love-handles the data gains. I suspect this might be due to the Gridfit function (see MATLAB files repository) I used for regridding the data. Gridfit.m uses an extrapolant method. My suspicion is it is trying to fill out the square of the data matrix and is accomplishing relatively correct values for near-by-data that is outside the scanned range. I’ll try it again with regrid or something similar in the future when I have time.

If anyone knows where the current site for XRDMLread.m is, I’d love to link to it. It appears the site may be down (graduated student I suspect). You can obtain the wonderful XRDMLread.m function and examples on the XRDMLread.m website. For now, I have to wait until I hear from the authors before I can share the file. I also don’t yet trust my icky 3D code, so I prefer not to release that until I have things hashed out. Sorry!

I’m extremely happy that Panalytical has published their XRDML file format and that the makers of XRDML.m have released their .m files for MATLAB. In the past, when Philips had the Xpert systems, the data was stuck for the most part in proprietary data formats. [You could slice the data and output in ascii- but making that work was a pain- which is why I never released that previous code.] I’m much closer to the 3d plotting now, and hope to finish it up before the thesis (my primary work which is not this plotting) is published.

Wishing you luck in you research!

AVS-Boston next week!

The society formerly known as the American Vacuum Society (AVS) is holding their international conference in Boston, MA next week! And I’ll be there! [Exciting!] If you are going to be there, drop me a line on the blog and we can snag a coffee or beer together.

The programs and cards sent out may have a familiar image! :)

My AFM image of the CuInSe2 Bicrystals I grow in our lab won second place in the Art-Zone competition last year! It was great fun! [Thanks goes to AVS for being a fantastic organization!]

AVS ArtZone Second Prize Winner- CuInSe2 Bicrystal

Wish me luck with my talk!! :)

Marge Simpson On Graduate School…

Those of you who know the Rockett group well, have likely seen this video. It’s completely hilarious. Anyone who’s ever been in Graduate School will love it…

Simpsons on Grad School @ Yahoo! Video

Quick One: UIUC Thesis Class Breaks ChapterBib (LaTeX)

I could not decide exactly how to post this… searching high and low, I couldn’t find the answer to my problem. I felt, in the very least, it needed to be posted here. So, I’ve decided to focus on the problem only. Then, in a future post, I’ll describe in more detail how I go about doing my research writing using LaTeX [wikipedia]. So, my basic comment is: I write in LaTeX, BibTeX, etc., and the following will help only a few people doing the same, and doesn’t actually offer a solution right now. :) [Boy, aren't I helpful?]  (click through to read more…)

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Published in the Journal of Applied Physics…

Well, I’m finally published in my current field.  It took a very very long time to get this paper published.  All sorts of reasons for the delay.  In fact, this work was originally started in 2004  (our first bicrystal was successfully grown in ’04).  During research group meeting, I made an under the breath comment something akin to: “Well, darnit, it’s too bad we can’t study a single grain-boundary, because then everything would be so much easier…”  Prof. Rockett looked over to me and smiled: “But, Allen, we can study a single grain-boundary!  That’s a great idea!”  So, the bicrystal project was started.

We were able to obtain a bicrystal GaAs wafer from Wafer Technology Limited Co. (UK); I requested a bad growth, with crystallites as large as possible.  I’ll be forever indebted to the great guys at Wafer Technology for their quick grasp of what I was looking for.  After visiting our group in 2006, S. Seibentritt at HMI (now at Lüxenbourg) started similar work.

While this current paper isn’t perfect, it went through numerous revisions.  Most of the extensive EBSD calculations didn’t make the paper.  Subsequent papers will likely revisit the disorientation discussion.

Epitaxial growth of very large grain bicrystalline Cu(In,Ga)Se2 thin films by a hybrid sputtering method
J. Appl. Phys. 103, 083540 (7 pages) (2008)

Unfortunately, there was an error we missed in the proof.  The paper is currently missing Figure 2(c): The cross-sectional HRTEM image (the hard work of C. Lei).  The image can be found here: Cross-Sectional HREM image of Cu(In,Ga)Se2 bicrystal, hosted at Prof. Angus Rockett’s research group’s webpage.

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A Quick Introduction...

I'm a graduate student (PhD Candidate) at the University of Illinois at Urbana-Champaign.

I've studied and researched in two fields of Materials Science and Engineering (Polymers and Semiconductors). My interests are as diverse as my musical tastes and I usually have my hand in some crazy project during my free time.

I'm available for consulting and have access to a world-renown materials research user-facility supported by the D.O.E. If you would like to know more, please contact me.

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