@article{zoellner_stuart_chung_dougherty_jones_maggard_2016, title={CuNb1−xTaxO3 (x ≤ 0.25) solid solutions: impact of Ta(v) substitution and Cu(i) deficiency on their structure, photocatalytic, and photoelectrochemical properties}, volume={4}, ISSN={2050-7488 2050-7496}, url={http://dx.doi.org/10.1039/c5ta06609c}, DOI={10.1039/c5ta06609c}, abstractNote={Solid solutions of Cu(I)-containing oxide p-type semiconductors provide key opportunities to probe the fundamental relationships between chemical compositions and crystal structures, bandgap sizes, band energies, and photoelectrochemical properties. Members of the CuNb1−xTaxO3 (0 < x ≤ 0.25) solid solution have been synthesized via high temperature solid-state methods. The structure of CuNbO3 was found to be Cu-deficient Cu0.965NbO3 after heating in air at 250 °C for 3 hours, i.e., under similar conditions as those used to prepare it as a polycrystalline film. Powder X-ray diffraction techniques confirmed the purity of each composition up to x ≤ 0.25 and the lattice parameters were refined as the molar ratio of Nb(V) and Ta(V) was varied (a = 9.499 to 9.506 A, b = 8.439 to 8.451 A, c = 6.768 to 6.781 A and β = 90.847 to 90.694°). An increase in the amount of Ta(V) yielded a small blue shift of the bandgap size from ∼1.89 eV to ∼1.97 eV for CuNb1−xTaxO3 from x = 0 to 0.25. Polycrystalline films of each member of the CuNb1−xTaxO3 solid solutions produced relatively comparable p-type photocurrents of up to −0.5 mA cm−2, while the stability of the cathodic photocurrent also remained similar with increasing Ta(V) content. Mott–Schottky analysis of CuNb1−xTaxO3 showed that the conduction band edge of −1.5 (vs. SHE) provides a sufficient overpotential (∼800 mV) to drive the reduction of water to hydrogen gas at the surface. The capability of the solid solutions to drive hydrogen production was confirmed through suspended particle photocatalysis. Further characterization of the CuNb0.91Ta0.09O3 composition included scanning electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analyses. These data show that Cu(I) is oxidized to Cu(II) as CuNb1−xTaxO3 is heated in air. Thus, the formation of Cu(II) rich regions at the surface, together with the Ta(V) content, are found to play important roles in the stability and magnitude of the cathodic photocurrents produced under visible-light irradiation. Importantly, these results demonstrate that solid solution compositions can be used in films for solar energy conversion, notwithstanding their inherent atomic disorder.}, number={8}, journal={Journal of Materials Chemistry A}, publisher={Royal Society of Chemistry (RSC)}, author={Zoellner, Brandon and Stuart, Sean and Chung, Ching-Chang and Dougherty, Daniel B. and Jones, Jacob L. and Maggard, Paul A.}, year={2016}, pages={3115–3126} }
 @article{stuart_gray_nevola_su_sachet_ulrich_dougherty_2016, title={Magnetoelectric oxide films for spin manipulation in graphene}, volume={10}, ISSN={["1862-6270"]}, DOI={10.1002/pssr.201510433}, abstractNote={The challenge of creating a graphene spin field effect transistor (spin‐FET) demands a magnetic gate dielectric material whose magnetization can be switched electrically. We have grown films of Cr2O3 on top of graphite and graphene by pulsed laser deposition that shows this crucial functionality. We demonstrate that the Cr2O3 films are magnetoelectric by poling them in combined electric and magnetic fields and then using magnetic force microscopy to observe spontaneous surface domain structure as a function of poling field. In addition, we show that the electric field created by a conducting AFM tip can be used to write magnetic patterns in the film that demonstrate the kind of continuous magnetoelectric control needed for a prototype spin‐FET. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)}, number={3}, journal={PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS}, author={Stuart, S. C. and Gray, B. and Nevola, D. and Su, L. and Sachet, E. and Ulrich, M. and Dougherty, D. B.}, year={2016}, month={Mar}, pages={242–247} }
 @article{mcafee_gann_guan_stuart_rowe_dougherty_ade_2014, title={Toward Single-Crystal Hybrid-Carbon Electronics: Impact of Graphene Substrate Defect Density on Copper Phthalocyanine Film Growth}, volume={14}, ISSN={["1528-7505"]}, DOI={10.1021/cg500504u}, abstractNote={Graphene has long been recognized as a potential replacement for indium tin oxide as a transparent conducting substrate that may not only be cheaper to manufacture but also may provide mechanical flexibility and templating for preferential organic film growth. Here, we report the discovery that the thin film growth mode and crystal structure of copper phthalocyanine (CuPc), a prototype organic semiconductor, is extremely sensitive to even atomic-scale defects (e.g., steps) on the graphene surface and that high quality films can be grown with a well-defined crystal orientation that should be favorable for optimized solar cell applications. The initial growth involves flat-lying copper phthalocyanine molecules in a triclinic brickstone crystal with (012) orientation. Thicker films on pristine graphite, as well as thin films on lower quality graphene, show an orientational transition to the flat-lying (112)-oriented brickstone, which nucleates near film defects and grows in more compact 3D islands. The thi...}, number={9}, journal={CRYSTAL GROWTH & DESIGN}, author={McAfee, Terry and Gann, Eliot and Guan, Tianshuai and Stuart, Sean C. and Rowe, Jack and Dougherty, Daniel B. and Ade, Harald}, year={2014}, month={Sep}, pages={4394–4401} }
 @article{stuart_satchet_sandin_maria_rowe_dougherty_ulrich_2013, title={Smooth MgO films grown on graphite and graphene by pulsed laser deposition}, volume={31}, ISSN={["2166-2746"]}, DOI={10.1116/1.4818511}, abstractNote={Pulsed laser deposition was used to grow thin (1–100 nm) magnesium oxide films directly on graphite and epitaxial graphene on SiC(0001). The authors observe very smooth (typical rms roughness of ∼0.4 nm) film morphologies that are nearly independent of film thickness and conformal to the substrate for films grown on room temperature substrates. Surface roughness is less than 1 nm for thicknesses up to 100 nm and is independent of oxygen background pressure during growth. X-ray diffraction shows no evidence of crystallinity for films grown on room temperature substrates but shows ⟨100⟩ texture for films grown on heated substrates that also have very rough surface morphologies. X-ray photoelectron spectroscopy shows hydroxylation of films due to air exposure that can only be partially removed by annealing, indicating the presence of atomic defects in the films.}, number={5}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Stuart, Sean C. and Satchet, Edward and Sandin, Andreas and Maria, Jon-Paul and Rowe, John E. and Dougherty, Daniel B. and Ulrich, Marc}, year={2013}, month={Sep} }