####################################################
# Karapetrova Evguenia <jenia@anl.gov>
# requesting 5 days, at minimum=3 days
# beamline 33BM, Study of the Structural Relaxation Process of Epitaxially grown Fe on GaAs(001).
# instrument 33BM-C fourc
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# top:/home/www/beamtime-requests/req01015.txt
# UNICAT Member Beam Time Request  #1015
# created Thu Aug 03 17:05:43 CDT 2006
####################################################

apsrun:
	2006-02

beamline:
	33BM

collaboration:
	No

collaborator_Jenia:
	ON

contact:
	jenia@anl.gov

days:
	5

description:
	For the 3rd run period
The Fe-GaAs (001) structure has been the primary focus of 'spin' resolved current injection studies. This interfacial system has been among the most efficient spin injectors (Fe-AlGaAs-GaAs has reported higher spin injection efficiency). The effect of 'spin scattering' or loss of spin oriented current remains the overwhelming issue. It has also been found that annealed Fe films at 200 C significantly improves the spin injection efficiency, beyond this point the efficiency drops very quickly with increasing annealing temperature.

The focus of this experiment is to continue investigating the structure of  Fe on GaAs(001). We have pre-grown Fe films epitaxially grown on GaAs(001) where the Fe ranges from 4Å to 90Å and the samples have been capped with 30Å of Al. A series of samples have also been annealed from 150C through 200C and up to 300C, in order to span the loss of spin injection.

The lattice length of GaAs is almost twice that of Fe with a 1.4% lattice mismatch, with this Fe grows cube on cube. Thus at low coverage the Fe is in the process of relaxing from the matrix created by the substrate surface. Due to the cubic bcc structure of the Fe and the diamond structure of the GaAs, the allowed Fe reflections will closely overlay with the GaAs reflections


We plan to initially repeat HK mesh scans around both the (22.1) & (-22.1) GaAs peaks of the 13.5A Fe film thickness at several temperatures, in order to investigate the in plane relaxed Fe changes with the annealing process. Coupled to this we plan to measure the out of plane (004)GaAs to also understand the relationship between the out of plane Fe lattice changes and the in plane lattice changes.

Due to the close overlap between the reflections it is important to reduce the  intensity of the GaAs reflection tails. Using a Si analyzer crystal will, by increasing the resolution suppress the GaAs tails.  One potential technique will also be to avail of ‘Anomalous Scattering’ to either suppress or enhance the signal of a specific element. We plan to scan through the Fe K edge in order to take advantage of selecting an energy to enhance the Fe signal.

equipment_required:
	

experiment:
	Study of the Structural Relaxation Process of Epitaxially grown Fe on GaAs(001).

foreign_nationals:
	

hazards:
	

instrument:
	33BM-C fourc

instrument_other:
	

minimumdays:
	3

name:
	Karapetrova Evguenia

new_request:
	ON

nonmembers:
	Philip Ryan

submit:
	Submit

unacceptable_dates:
	Thanksgiving holidays

z34ID_details:
	


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