#
# arev:/usr/local/unicat/unireq/beamreq/req00084.txt
# UNICAT Member Beam Time Request  #84

# created Fri Oct 01 11:53:30 CDT 1999
#

collaboration:
	Yes

collaborator+Hawoong:
	on

days:
	6

description:
	       Structural phase transitions of Sn adsorbed on Ge through
	 anomalous scattering.  This system undergoes a 2-D CDW transition
	 characterised by different surface reconstructions (3x3 -
	 root3 x root3).
	
	        We will use CTR analysis to establish location of the adatoms 
	in both phases, and highlight the adsorbate contribution to the
	 scattering by taking measurements at x-ray energy above and below
	 the Sn absorption edge.  The surface quality will be documented
	 during preparation and experiment, as it has been shown to have a 
	non-trivial effect on the clarity of the phase transition.  Previous
	 X-ray diffraction experiments on this system have all been hampered
	 by poor sample quality and poor signal to noise ratio.    
	

equipment+required:
	    MBE chamber, LN2 cooled sample holder 

experiment:
	Phase transitions in Sn/Ge(111)

hazards:
	     No special procedures needed. All samples are in solid form and
	 are stable in air. Do not ingest or inhale. 
	

name:
	T.-C. Chiang

new+request:
	on

nonmembers:
	

station:
	33ID-E

unacceptable+dates:
	Nov 24 - 28



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