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