Thomas McConkie, David Allred, Gus Hart, Brian Hicks
What missing crystal structures?Setup and PreparationExperimental MethodsResultsContinuing the Search
“Where are natures missing structures?”Gus Hart, Nov. 11, 2007
L13 Structure
Vacuum systemRoughing, Turbo and Cryo Pumps.Leaked checked system to minimize
unwanted interference by outside air. Base pressure of (~10-6 torr).
Sputtering Gun
SputteringEven coating on all
surfacesSputtering plasma: Ar+PtCd
Magnetron SputteringLower pressure
(~10-3 torr).Better quality
Composition
Crystal Structur
e
EDAXEnergy dispersive X-ray spectroscopy
STE
M
Scanning Transmission electron microscopy
Pure platinumTEM grid substrateComposition:
PtCrystal Structure:
Face Center Cubic (FCC)
Constructive Interference
Destructive Interference
Patterns of high and low intensities due to constructive and destructive interference of the incident beam (gives spacing in the crystal structure)
FCC Peaks
Super lattice peaks
Super lattice peaks
Platinum and CadmiumVery little Cadmium Substrate:
TEM GridsComposition ratio:
~1 Cd : 3Pt on Cd rich side.
More Cadmium
More Platinum
~3 Pt : 1 Cd ratio was achieved.
Were not able to detect any of the super lattice peaks.
Where are you?
Grow thicker sample and subject to bulk x-ray analysis~8 μm thick
Look for super lattice peaks.Check for Composition using EDAX and
crystal structure using STEM.
Special thanks to :NSF
Richard VanfleetJeff FarrerLiz Strein
Branton Campbell