####################################################
# Martin Holt <mvholt@uiuc.edu>
# requesting 3 days, at minimum=3 days
# beamline 33ID, "Phonon softening and surface effects in the 110K phase transition of SrTiO3"
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# top:/home/www/beamtime-requests/req00288.txt
# UNICAT Member Beam Time Request  #288
# created Tue Aug 27 16:25:51 CDT 2002
####################################################

beamline:
	33ID

collaboration:
	Yes

contact:
	mvholt@uiuc.edu

days:
	3

description:
	Diffuse scattering will be collected over a temperature range of 75K-300K at the [1/2 1/2 1/2] point in reciprocal space.  Analysis of the TDS component (previously measured) has shown phonon softening leading up to the 2x2x2 displacive phase transition nearly identical to neutron scattering results.  However a small, sharp central component appears near 120K, previously attributed in the literature to a near-surface structural phase transition at an elevated temperature relative to the bulk.  This observed central component will be established to be a surface phenomena by taking data at several photon energies along the Sr edge.  This should dramatically change the scattering volume for the bulk-like TDS component while leaving the central (surface) component unchanged.  Taking this data also as a function of temperature may also distinguish between surface strain vs. dislocations as the driving force behind this surface phase transition (accretion of a phase transition in a strain field would change spatially with temperature whereas a transition around static dislocations would remain the same).
	
	This data will also be taken on a second sample which has been annealed in oxygen to have the surface recover from mechanical polishing.

equipment+required:
	diffractometer, He displex

experiment:
	Phonon softening and surface effects in the 110K phase transition of SrTiO3

foreign+nationals:
	

hazards:
	cryogenic hazard - closed cycle He displex

minimumdays:
	3

name:
	Martin Holt

new+request:
	on

nonmembers:
	

unacceptable+dates:
	November 1-20


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