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# Gregory Thompson <thompson.748@osu.edu or 614-292-6263>
# requesting 3 days, at minimum=3 days
# beamline 33BM, "Glancing and Grazing Incident X-ray Diffraction of Metallic Thin Film Multilayers"
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# top:/home/www/beamtime-requests/req00262.txt
# UNICAT Member Beam Time Request  #262
# created Mon Apr 15 15:55:02 CDT 2002
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beamline:
	33BM

collaboration:
	No

collaborator+Paul:
	on

contact:
	thompson.748@osu.edu or 614-292-6263

days:
	3

description:
	Purpose: A series of Nb/Ti, Nb/Zr, and Al/Ti multilayers have been sputtered deposited. Each individual layer thickness is 1-5 nm in thickness with the entire multilayer (40-80 layer pairs) film thickness being 200-500 nm. Experiemental work is being conducted to determine phase stability in each of the layers as a function of length scale and volume fraction of material in a bilayer pair.  Novel phase stabilities that have been observed in plan view (and cross section) TEM include hcp Nb, bcc Ti, bcc Zr, and fcc Ti.  
	
	Problem: To help clarify that these transitions are real and not artifacts of TEM sample preparation, XRD is needed. Since these films have textured growth of the closed packed planes parallel to the surface of the substrate (Si), only the closed packed orientation g-vectors [(0002), (011), or (111)] diffract in a traditional XRD reflection set up. This can make phase identifaction difficult, particualry becuase only a limited # of {hkl} peaks are seen due to the texture.  Furthermore, as the layers are reduced in thickness, coherent scattering from the layering of the multilayer results in an averaging of the individual {hkl} closed packed plane's diffracted intensities resulting in a single peak. 
	
	Solution: Glancing incident XRD from the APS will allow a high intensity source to be used to sample in-plane g-vectors, hence giving the {hkl} of the individual phases. The film, haivng randomly orientated grains in-plane (non-textured), will allow many more g-vectors to diffract from the individual {hkl} phases. Thereby making phase identification more conclusive then from a single, textured peak in the reflection XRD mode. Additionally, the coherent scattering effects of the layering of the multilayer will not hinder {hkl} reflections since sampling is in-plane. Little to no sample preparation is needed for this experiment. These experiments are critical in clearly demonstrating the validity of structural transitions in thin multilayered films.
	
	While at the APS, these same samples will be set-up to diffract in a grazing incident mode. In this arrangement, diffraction runs are from 0.2 - 8 degrees 2-theta. Diffraction results from the layering of the multilayer and not from individaul {hkl} phases of the film's material.  The d-values corresponding to the diffracted intensities give the bilayer spacing of the multilayer (a critical parameter to determine length scale for transitions) as well as quantitative information about the abruptness of the interface by the breath of the diffracted intensity peak. In our models, the interface is a key feature that determines phase stability. 
	
	Samples: The samples will be at least 1 cm x 1 cm in size. The samples have already been deposited and can be run at APS's earliest convience. Collabration with APS staff on running these experiments is preferred since it is estimated that one or two visits will only be required. The total sample count will be 15-20. They include one hcp Zr/bcc Nb, one hcp Ti/bcc Nb, three bcc Zr/bcc Nb, one bcc Ti/bcc Nb, one hcp Zr/hcp Nb, one fcc Ti/fcc Al, one hcp Ti/fcc Al, and a couple alloyed verions of Ti/Nb.

equipment+required:
	Talked to Dr. Paul Zschack about the experiment and its needs. I believe I will only need the equipment associated with a basic powder XRD run, e.g. ability to rotate specimen holder at different chi values to sample the specimen.

experiment:
	Glancing and Grazing Incident X-ray Diffraction of Metallic Thin Film Multilayers

foreign+nationals:
	Gregory Thompson is a US citizen. Dr. Rajarshi Banerjee is from India and has begun submitting the proper forms for access. If beam time is made available prior to his approvement to come to ANL, that will be fine. Greg Thompson will come alone. We are primarly interested in running the experiments when it it fits in your earliest schedule.

hazards:
	None

minimumdays:
	3

name:
	Gregory Thompson

new+request:
	on

nonmembers:
	

unacceptable+dates:
	May 24-May 27 (Memorial Day weekend)
	July 3-7 (July 4th holiday week)
	*If these would be my earliest (or only) dates, I can make arrangements to be at APS, but would perfer to avoid them if possible. Thanks.


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