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Published December 2017 | Supplemental Material
Journal Article Open

Effects of surface condition on the work function and valence-band position of ZnSnN_2


ZnSnN_2 is an emerging wide band gap earth-abundant semiconductor with potential applications in photonic devices such as solar cells, LEDs, and optical sensors. We report the characterization by ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy of reactively radio-frequency sputtered II–IV-nitride ZnSnN_2 thin films. For samples transferred in high vacuum, the ZnSnN2 surface work function was 4.0 ± 0.1 eV below the vacuum level, with a valence-band onset of 1.2 ± 0.1 eV below the Fermi level. The resulting band diagram indicates that the degenerate bulk Fermi level position in ZnSnN_2 shifts to mid-gap at the surface due to band bending that results from equilibration with delocalized surface states within the gap. Brief (< 10 s) exposures to air, a nitrogen-plasma treatment, or argon-ion sputtering caused significant chemical changes at the surface, both in surface composition and interfacial energetics. The relative band positioning of the n-type semiconductor against standard redox potentials indicated that ZnSnN_2 has an appropriate energy band alignment for use as a photoanode to effect the oxygen-evolution reaction.

Additional Information

© 2017 Springer-Verlag GmbH Germany. Received: 17 May 2017; Accepted: 27 October 2017; First Online: 07 November 2017. We gratefully acknowledge support from the Dow Chemical Company under the earth-abundant semiconductor project. We also acknowledge the Joint Center for Artificial Photosynthesis and the Molecular Materials Research Center of the Beckman Institute at Caltech for instrument access. The authors thank Bruce Brunschwig and Kimberly Papadantonakis for guidance. Compliance with ethical standards. Funding: Dow Chemical Company, Caltech Molecular Materials Research Center.

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August 19, 2023
October 17, 2023