| AVS 62nd International Symposium & Exhibition | |
| Electronic Materials and Processing | Monday Sessions |
| Session EM+AS+SS-MoM |
| Session: | Rectenna Solar Cells, MIM Diodes, and Oxide Interfaces |
| Presenter: | Tiffany Kaspar, Pacific Northwest National Laboratory |
| Authors: | T.C. Kaspar, Pacific Northwest National Laboratory D.K. Schreiber, Pacific Northwest National Laboratory S.R. Spurgeon, Pacific Northwest National Laboratory S.A. Chambers, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
Hematite, α-Fe2O3, is an ideal photocatalyst to split water as a source of H2 fuel because it is non-toxic, Earth-abundant, stable in aqueous environments, and possesses a bandgap in the visible wavelength range (~2.1 eV). However, fast photogenerated electron-hole recombination, facilitated in part by slow carrier transport kinetics, has long been identified as a major obstacle in the utilization of hematite photocatalysts. A direct method to reduce photogenerated carrier recombination is to employ heterojunctions to spatially separate excited electrons and holes. Our approach is to engineer built-in electric fields by exploiting the band alignment characteristics of epitaxial Fe2O3/Cr2O3 heterojunctions. The Fe2O3-Cr2O3 system exhibits non-commutative band offsets which differ by approximately 0.4 eV depending on the order of deposition. The non-commutative band offset properties of Fe2O3-Cr2O3 interfaces can be utilized in a superlattice structure, deposited by oxide molecular beam epitaxy, to build up an intrinsic electric field; this potential may be sufficient to spatially separate photogenerated electrons and holes. We demonstrate precise control over the Fe2O3-Cr2O3 interface structure with atomic-resolution atom probe tomography and scanning transmission electron microscopy. Direct evidence that Fe2O3-Cr2O3 superlattice layers generate an intrinsic built-in potential is observed with x-ray photoelectron spectroscopy. The individual interfacial band offset values, and thus the overall potential, can be tailored by altering the cation stoichiometry at the interfaces. Doping the component layers to improve transport characteristics requires a deep understanding of the dopant-induced electronic structure changes. To illustrate how the built-in potential in optimized Fe2O3-Cr2O3 superlattice structures can be harnessed to drive holes to the surface and electrons into the bulk, photoconductivity and photochemical degradation results will be presented.