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 Co 3 O 4 films for testing catalyst during CO 2 hydrogenation to investigate, mechanistically, how and why crystal facets influence catalyst reactivity and selectivity Background Hydrogenation Epitaxy Magnetron Sputtering + 4 + 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 spinel structure 1 Figure 5: XRD Spectra of films deposited on Silicon substrate Figure 4: Reference XRD Spectra of spinel structure Figure 9: Above: Spinel film deposited on Silicon, reduced completely in 2 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. 2. Power and oxygen flow rate can be varied during reactive sputtering depositions to investigate phase differences A very selective range of deposition parameters yields Co 3 O 4 spinel structure Several power and oxygen flow combinations yielded samples that show high possibility of epitaxy, whether Co 3 O 4 or 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 3 4 deposited on Silicon Bottom Left: Raman spectra of cubic CoO vs. spinel 3 4 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 Co 3 O 4 peaks