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# Greg Thompson <thompson.748@osu.edu or (614)486-4957(home) or (614)292-5695(work)>
# requesting 2 days, at minimum=1 days
# beamline 33ID, "Follow-up visit for Phase Identification of Nb/Zr Multilayers by Transmission XRD"
####################################################
# top:/home/www/beamtime-requests/req00296.txt
# UNICAT Member Beam Time Request  #296
# created Wed Oct 02 16:19:23 CDT 2002
####################################################

beamline:
	33ID

collaboration:
	No

collaborator+Paul:
	on

contact:
	thompson.748@osu.edu or (614)486-4957(home) or (614)292-5695(work)

days:
	2

description:
	In early August 2002 a set of transmission XRD scans (Beamline 33-ID) were conducted on several Nb/Zr and Nb/Ti multilayered thin films. Upon reduction of film thickness, these specimens exhibited metastable phases. Phase identification was done by plan-view TEM diffraction prior to this visit.  To ensure that the metastable phases were not artifacts of TEM specimen preparation, transmission XRD on the as-deposited films in the as-deposited state were conducted.  The films were grown on single crystal silicon wafers. 
	
	In this initial set of experiments, moderate success on phase identification was accomplished. But being the first set of experiments to be conducted in the transmission XRD mode for our group, some unanticipated experimental difficulties occurred.  In the original design of the experiment, the Si wafers, being single crystal, were going to be titled such that the Si Bragg reflections would not interfere with the diffracted intensities of the film.  This did occur.  But what was not initially foreseen was the level of the background intensity from the thermal diffuse scattering (TDS) of the Si.  The TDS often obscured the diffracted intensity which has made identification difficult and not as %91clear-cut%92 as initially hoped for.  This is particularly true for the TEM indexed hcp Nb phase.  This phase, which has not been observed in nature, was a prediction of our model.
	
	From the experience of my initial visit, I have learned what I would need to do to ensure success for a second round of XRD scans. I plan on grinding my Si wafers to be less then 80 microns in thickness (they were originally 250-450 microns in thickness). Since absorption is exponential, this should greatly reduce the background TDS and allow the film intensity to be easily observed in the XRD scans. Furthermore from my initial visit, I have a clearer understanding on how to tilt the specimen to avoid the TDS bans that generated the high background and obscured the film peaks. Now that a wavelength has been established (15.05KeV) to meet the needs of the experiment, I will have all the necessary scan regions pre-determined. I would only request initial instruction on the alignment of the beam.  The experimental set up is quite simple. A tube was placed from the source to the goinometer to reduce scattering in the air (10 minutes to set up). The individual wafers were attached to the goinometer%92s mounting block by a sticky red paste.  Once the wafer was aligned to the goinometer block and to the beam (10-20 minutes to set up), all future specimens were easily loaded. Total scan times lasted 20-30 minutes. 
	
	If possible, I would like to request the opportunity for a short stay (one-day) to re-scan a selected few specimens. I would be willing to fit in between two users, conduct the experiments in the evening or on the weekend or whatever time may be available in the near future. This follow-up experiment would help make the data much clearer to understand and provide the last piece of the puzzle I need for my dissertation. I would be willing to accommodate any schedule requirements.
	
	Thank you for your time and consideration of this request.  I eagerly look forward to your reply.

equipment+required:
	None

experiment:
	Follow-up visit for Phase Identification of Nb/Zr Multilayers by Transmission XRD

foreign+nationals:
	None

hazards:
	No hazards

minimumdays:
	1

name:
	Greg Thompson

nonmembers:
	None

unacceptable+dates:
	None


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