Christina Engler, Jonathan Kenneth Bunn, Cun Wen, Jason Hattrick-Simpers, Jochen Lauterbach

Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208

Epitaxial Cobalt Oxide Thin Film Synthesis

via Magnetron Sputtering

Goal• Grow epitaxial Co3O4 films for testing

catalyst during CO2 hydrogenation to

investigate, mechanistically, how and

why crystal facets influence catalyst

reactivity and selectivity

𝐂𝐎𝟐

Background𝐂𝐎𝟐 Hydrogenation

Epitaxy

Magnetron Sputtering

𝐂𝐎𝟐 + 4𝐇𝟐 𝐂𝐇𝟒 + 𝟐𝐇𝟐𝐎

Substrate

• Deposited material and substrate

have minimal lattice mismatch

• Preferentially depositing one desired

crystal plane

Procedure

Calibration Depositions

Deposited

Material

X-Ray Diffraction

Raman Spectroscopy

Conclusions

Future Work Continue characterization of current films

to look for epitaxy and cobalt phases

Tune reactive sputtering parameters to

maximize desired texturing

Investigate if other crystal planes can be

grown epitaxially using other sapphire

substrates (with different crystal planes at

the surface)

Test catalyst activity and selectivity via

In-Situ PM-IRAS Tests

The National Science Foundation (NSF-EEC-

1358931)

Dr. Jochen Lauterbach, Dr. Jason Hattrick-

Simpers, Dr. Cun Wen, Jonathan Kenneth Bunn,

and Patrick Barboun

SAGE

Acknowledgements

References

How do the power and partial pressures

of Oxygen during deposition influence

the phase of Cobalt Oxide deposited?

Calibration

Depositions

Deposit

Films

Characterize

Films

XRD Raman

Figure 2: The

deposition rate

during reactive

sputtering decreases

as the target is

poisoned, where the

top layer of the

target is oxidized,

because the

deposition rates of

oxides are much

slower than metals

Figure 10: After making 28 different films and characterizing them, a

phase diagram plotting the power and oxygen flow rate of each sample

was made to demonstrate the Cobalt Oxide phases deposited for each

sample condition.

Figure 3: The unit cell of the 𝑪𝒐𝟑𝑶𝟒

spinel structure 1

Figure 5: XRD Spectra of films deposited on

Silicon substrate

Figure 4: Reference XRD Spectra of

𝑪𝒐𝟑𝑶𝟒 spinel structure 𝟐

Figure 9: Above: Spinel film deposited on

Silicon, reduced completely in 𝐻2 gas.

Reduced at 273 ℃

In-Situ

Figure 6: Possibly slightly textured films, either the (311)

spinel plane or the (111) cubic plane at ~36.4 deg. 2𝜽.

Power and oxygen flow rate can be varied

during reactive sputtering depositions to

investigate phase differences

A very selective range of deposition

parameters yields Co3O4 spinel structure

Several power and oxygen flow

combinations yielded samples that show

high possibility of epitaxy, whether Co3O4or CoO, and can be investigated further

with other spectroscopic methods

Figure 7: XRD Spectra of films deposited on

sapphire substrate, only spinel structures shown

Figure 8: Top left: Raman spectra of cubic

CoO vs. spinel 𝐶𝑜3𝑂4 deposited on Silicon

Bottom Left: Raman spectra of cubic CoO

vs. spinel 𝐶𝑜3𝑂4 deposited on Sapphire

(1): J. Chen, X. Wu, A. Selloni. Electronic Strucutre and Bonding

Properties of Cobalt Oxide in the Spinel Structure. Phy. Rev. B,

85(2012), p. 085306

(2): Xie, X. W.; Shang, P. J.; Liu, Z. Q.; Lv, Y. G.; Li, Y.; Shen, W. J.

Synthesis of Nanorod-Shaped Cobalt Hydroxycarbonate and Oxide with

the Mediation of Ethylene Glycol. J. Phys. Chem. C 2010, 114,

2116−2123.

(3): V. G. Hadjiev, M. N. Iliev, I. V. Vergilov, J. Phys. C: Solid State

Phys. 1988, 21, L199.Figure 1: Argon plasma(3)

Silicon

Co3O4 peaks