Large Single Crystal Growth: Traveling Solvent Floating Zone

1
Large Single Crystal Growth Traveling Solvent
Floating Zone
S. Wilson1,2, B. Freelon1,2, E.
Bourret-Courchesne2,3, Z. Hussain3, and R.
Birgeneau1 1 Department of Physics, University of
California, Berkeley, California 94720, USA 2
Lawrence Berkeley National Laboratory, Advanced
Light Source, Berkeley, California 94720, USA 3
Materials Sciences Division, Lawrence Berkeley
National Laboratory, Berkeley, California 94720,
USA
Current Synthesis Efforts
Why Use Traveling Solvent Floating Zone?
Feed rod
Advantages
Experiments

• La2CuO4
• Parent compound of high temperature
  superconductors
• Superconductivity arises upon doping holes into
  the CuO2 planes
• Holes introduced via Sr alloying or oxygen
  intercalation
• Staged La2CuO4y
• Achieved through electrochemical doping La2CuO4
• Renders precise control of dopant disorder
• Stage-4 oxygen orders into three dimensional
  crystal within the lattice
• La2-xSrxCu1-yZnyO4
• Zn substitution into the CuO2 planes of
  La2-xSrxCuO4 rapidly suppresses Tc
• Simultaneously induces localized magnetic states
• Drastically modifies magnetism observed within
  Zn-free variants

• Neutron Scattering
• ARPES (single crystal)

• Large Scale Single Crystals
• Low Contamination

Flux
Melt Zone
Canon Model SC1-MDH

• Comprised of two ellipsoidal, gold-plated
  mirrors
• Halogen light bulb located at either focus
  generates heating zone
• Temperature within the zone can reach greater
  than 2100C
• Extremely sharp melting zone possible
• Motorized shafts translate the raw
  polycrystalline feed material through the
  melting zone
• Precisely controlled range of speeds (0.02 mm/hr
  to 50 mm/hr)
• Versatile range of stable growth rates
• Crystal growth within a sealed quartz tube 
• Allows for controlled gas environment
• Capable of sustaining pressures up to 10
  atmospheres
• Versatile for synthesizing single crystals of a
  large variety of crystalline systems

Grown Crystal
Fig. 6 Crystal Structure of La2CuO4 The atomic
unit cell for La2CuO4 is shown with the red
hatched region enclosing the lower charge
reservoir region where Sr substitutes onto the
La-site.
Growth Start
Stabilized Growth
Fig. 4 Image from stabilized growth
Fig. 3 Image from beginning of growth
This feed rod is connected to the nucleated
crystal below the heating zone via the
crystalline melt.  This melt connects the two
rods by surface tension only and, in the case of
incongruent crystal growth, contains
the necessary chemical solvent.  The solvent
incorporates into the feed rod, effectively
lowering its melting point and enables the growth
of a large variety of systems.  The solvent
itself "travels" to remain in the crystalline
melt as the feed rod and grown crystal are
translated downward.
Traveling Solvent Floating Zone Technique
Ellipsoidal Mirrors
Fig. 7 Picture of Staged La2CuO4? Oxygen
orders in a staging pattern along the c-axis.
Stage-6 behavior is illustrated here. From B.
Wells et al., Science 277, 1067 (1997).
Learn More
M.A. Kastner and R.J. Birgeneau. Rev. of Modern
Physics, 70, 897 (1998). Chul-Ho Lee et al.,
Super. Sci. Technol. 11, 891 (1998).
Fig. 1 Mirror Image Furnace Diagram Schematic
showing the optics and positioning of furnace
components. Light from the two bulbs focused
onto junction between feed rod and nucleated
crystal
Fig. 2 Crystal Growth using TSFZ Illustration
showing the use of a solvent during the growth of
systems which melt incongruently. The grown
crystal composition results from the solvent
chosen and the systems phase diagram.
Acknowledgements
TSFZ Details
Jerry Kekos, Edith Bourret, Ipsheeta Furtado

• Compelling advantage in the absence of any
  crucible contact with the crystal during growth 
• Eliminates crucible contamination from the
  crystal's reaction with a crucible or its
  environment during growth  
• Growth instead via a suspended polycrystalline
  "feed" rod which is translated downward through
  the heating zone 

Further information
Sealed growth environment
Please contact SDWilson_at_lbl.gov. More
information on this and related projects can be
obtained at http//birgeneau.berkeley.edu.
Fig. 5 Photo of Canon SC1-MDH growth
assembly The two mirror enclosure seals around
the quartz growth tube.