Ian Curtin
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Synthesis and Characterization of Zinc Tin Nitride
Ian Curtin
Group III Nitrides
GaN, InN, AlN Widely studied group of materials Applications in optoelectric devices:
LED Lights Lasers
Zn-IV Nitrides
ZnGeN2, ZnSnN2, ZnSiN2
Analogous to group III Nitrides Band gaps Lattice structure
Distinctly different predicted properties: Doping potential Defect properties
Plot of lattice constant vs band gap energy for group III and Zn-IV Nitrides. ZnSnN2, and ZnSiN2
band gap values are from theoretical prediction. ZnGeN2 band gap value is experimental
InN Completed 1st successful
growth of a semiconductor in this system
Wurtzite (hexagonal) symmetry
SEM image of etched InN sample at 5,000x
EXD Data of etched InN
ZnSnN2
Zn-IV nitride analog to InN Theory predicts a band gap energy of 1 eV
(± 1 eV ?) To date has not yet be synthesized Orthorhombic (not perfectly wurtzite) lattice structure
Due to Zn and Sn different bond lengths Stucture more closely matched with GaN
Growth System: high vaccum plasma chamber
RF Plasma Source
Growth Chamber
Turbo Pump
Roughing Pump
Crucible and heater
System Changes
Installed new turbo pump Lowered crucible and
heater Allows observation of
sample during growth Soon we’ll install a longer
quartz tube Allowing increased amount
of activated Nitrogen reaching the melt
Before After
Creating a Zinc-Tin Alloy Grow ZnSnN2 from the melt with a
Zn-Sn alloy Melt pellets of Zn and Sn together in
a crucible: Zn has a thick oxide layer that must
be removed Expose to a 200 W hydrogen plasma
and heat to a temperature above eutectic melting point for 1 hour
Zinc Nitrides: Zn3N2 stable under growing
conditions Supress by diluting Zn in Sn rich
mixture Sample 1: 9-91 at% ratio Sample 2: 22-78 at% ratio Sample 3: 29-71 at% ratio
Binary phase diagram of a Zn-Sn alloy
Growths
ZnSn alloy exposed to 290 W Nitrogren plasma at 400˚C for 3-4 hours
Pressure of 7 mTorr Nitrogen plasma left
on while sample cools to temperature below eutectic melting point
Results Have not yet confirm
growth of ZnSnN2
During the growth process all samples changed in color and texture after exposure to nitrogren plasma
Sample 1 most likely to have grown trace amounts of ZnSnN2 SEM and Optical images
displayed signs of crystalline morphology
EDX revealed the presence of Zn,Sn, and N
EDX Averaged over the surface of sample 1
Optical image of sample 1 taken at 500x
SEM image of sample 3
Phase Separation What happens as sample
cools? Changes from
homogenous liquid into distinct states of different compositions
Conclusions
Haven’t yet confirmed growth of ZnSnN2
Initial results showed small amounts of ZnSnN2 could’ve formed
More indepth analysis needed on certain features Saw strong evidence of phase separation Made positive changes to the experimental
package