RE: [Ifeffit] Substrate material question
Paul, Silicon is quite strong. However, it is also brittle. For detectors I have been able to bend 200 micron silicon to less than a 200mm radius. That should be plenty of strain. Virginia Semiconductor is great. Look at their double-side polished stock and you can typically find one or two batches with less than 200 micron thickness. Wafers thinner than 100 microns begin to get quite fragile. Jeremy Kropf Chemical Engineering Division Argonne National Laboratory -----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Paul Fons Sent: Tuesday, April 27, 2004 7:59 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] Substrate material question I have still not decided on the final substrate material, but I have a couple of samples coming from Dupont of polyimide (same composition as Kapton) material called vespel. It is essentially inert as one would expect (like Kapton), but due to differences in manufacture I understand it is hydroscopic. From this I assume that the reaction for making Kapton is diffusion limited and Vespel is essentially a "polycrystalline" -- in the sense there are grains between which water can absorb -- form of Kapton. The energy in question is 11.6 keV (the Ge edge). Si is an interesting idea but the loss for a 200 micron thick substrate is essentially 1/e. It is certainly worth considering for higher energies though! The 1/e value for polyimide is about 3500 microns in contrast, while the 1/e value for MgO is about 300. As in my experiment I want to create biaxial stress in a thin film on the substrate, I worry that the stress/strain curves for MgO are too stiff. On the other hand, thin S! i is a real possibility (darn, Si technology is everywhere!). I like the Si idea and might try that in parallel. Has anyone tried using thinned Si wafers (Virginia Technology ? sells mechanically thinned wafers I think -- I saw them at a MRS booth a long time ago). How fragile are the wafers? On 2004/04/28, at 0:32, Jeff Terry wrote: Hi Matt, Both items are good to know. I didn't realize that the laminated kapton structures still had good heat resistance. Jeff On Apr 27, 2004, at 10:22 AM, Matt Newville wrote: Hi Paul, I think you can get polyimide thicker than 175 microns. It may not go as Kapton, but maybe as Cirlex or Torlon or something else. I think goodfellow.com carries these in millimeter thick sheets and rods, and that they're still radiation and heat resistant. Goodfellow tends to be pricey, but has excellent information on thermal and mechanical properties. Using MgO, sapphire, or even diamond might be reasonable too. --Matt PS: I have a working build of PGPLOT with all of Aquaterm, X11, Postscript, and Png devices on Mac OS X. I'm still tweaking the makefile so that it links directly to the png objects to avoid possible conflicts with dynamic png and zlib libraries, but I should have a working ifeffit binary using this in a matter of days, and then be ready to tweak horae's Makefile.PL so that horae_update works. _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Dr. Paul Fons Senior Researcher National Institute for Advanced Industrial Science & Technology METI Center for Applied Near-Field Optics Research (CANFOR) AIST Central 4, Higashi 1-1-1 Tsukuba, Ibaraki JAPAN 305-8568 tel. +81-298-61-5636 fax. +81-298-61-2939 email: paul-fons@aist.go.jp The lines below are in a Japanese font 〒305−8568 茨城県つくば市東1−1−1 つくば中央第4 近接場光応用工学センター ポール・フォンス主任研究官
Continuing in the vein of marginally relevant questions (you need to take data before you can analyze it with horae!), I have yet another question. To make life more exciting, I would like to take a 4 m in vacuum undulator beamline that has a focussing mirror with a 250x600 micron spot size and focus down as much of the beam as I can to dimensions on the order of a micron (or a little bit bigger) using a monocapillary. I would then like to do microexafs with this setup. The brilliance of the undulator is about 5x10^15 in the range I am interested in (about 11-12 keV). Has anyone had any experience with this sort of focussing and might you recommend a company or spec to try? Thanks in advance. Paul
Hi Paul, I probably have as much experience with micro-XAFS as anyone on this list, and am willing to make a few comments. First, Steve Heald and Dale Brewe at APS/PNC-CAT have extensive experience making and using single capillaries for focussing -- probably more than anyone else. They're really the people to ask. Second, I believe there is not a commercial supplier of suitable capillaries, and that Heald and Brewe made essentially all of their own capillaries. After a few years of experience, I believe they could get 1 micron spots fairly routinely. Third, I think the consensus is that capillaries don't work too well for EXAFS. I wouldn't be willing to say that PNC-CAT has abandoned them, but I haven't seen capillaries used for this purpose in a long time. Without going into the details of the problems here, I can say that we at GSECARS and Heald etal at PNC-CAT regularly use 10cm long KB mirrors to focus APS undulator A to 2-3 microns for micro-XAFS, and that other beamlines at APS and other sources use such mirrors for micro-beam work as well. Fourth, Micro-EXAFS with a 1 micron beam and a 1 micron sample is challenging because of sample vibrations. But as the sample and spot size get to 5 to 10 microns, it works reasonably well. Many problems that appear to need 1 micron can get by with 5 microns, especially when the penetration depth is considered. Fifth, getting below 10 microns is heavily dependent on source characteristics, especially divergence. A 4m in vacuum undulator is an excellent start, but you might need to remove the larger beamline mirrors and slit down the source to get to 1 micron. Finally, It might be worth considering taking your experiment to an existing micro-EXAFS beamline, or visiting one ahead of time. ;). --Matt On Thu, 29 Apr 2004, Paul Fons wrote:
Continuing in the vein of marginally relevant questions (you need to take data before you can analyze it with horae!), I have yet another question. To make life more exciting, I would like to take a 4 m in vacuum undulator beamline that has a focussing mirror with a 250x600 micron spot size and focus down as much of the beam as I can to dimensions on the order of a micron (or a little bit bigger) using a monocapillary. I would then like to do microexafs with this setup. The brilliance of the undulator is about 5x10^15 in the range I am interested in (about 11-12 keV). Has anyone had any experience with this sort of focussing and might you recommend a company or spec to try? Thanks in advance.
Paul
participants (3)
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Kropf, Arthur Jeremy
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Matt Newville
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Paul Fons