Abstract
Proximity ferroelectricity is an interface-associated phenomenon in electric-field-driven polarization reversal in a non-ferroelectric polar material induced by one or more adjacent ferroelectric materials. Here we report proximity ferroelectricity in wurtzite ferroelectric heterostructures. In the present case, the non-ferroelectric layers are AlN and ZnO, whereas the ferroelectric layers are Al1−xBxN, Al1−xScxN and Zn1−xMgxO. The layered structures include nitride–nitride, oxide–oxide and nitride–oxide stacks that feature two-layer (asymmetric) and three-layer (symmetric) configurations1, 2–3. Ferroelectric switching in both layers is validated by multimodal characterization methods, including polarization hysteresis, anisotropic chemical etching, second harmonic generation, piezo response force microscopy, electromechanical testing and atomic resolution polarization orientation imaging in real space by scanning transmission electron microscopy. We present a physical switching model in which antipolar nuclei originate in the ferroelectric layer and propagate towards the internal non-ferroelectric interface. The domain wall leading edge produces elastic and electric fields that extend beyond the interface at close proximity, reducing the switching barrier in the non-ferroelectric layer, and allowing complete domain propagation without breakdown. Density functional theory calculations of polymorph energies, reversal barriers and domain wall energies support this model. Proximity ferroelectricity enables polarization reversal in wurtzites without the chemical or structural disorder that accompanies elemental substitution, opening new questions and opportunities regarding interface-based ferroelectricity.
| Original language | English |
|---|---|
| Pages (from-to) | 574-579 |
| Number of pages | 6 |
| Journal | Nature |
| Volume | 637 |
| Issue number | 8046 |
| DOIs | |
| State | Published - Jan 16 2025 |
Funding
The proximity ferroelectricity phenomenon was conceptualized, developed, initially demonstrated and validated with the support of the Center for 3D Ferroelectric Microelectronics (3DFeM), an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences Energy Frontier Research Centers program under award DE-SC0021118. Piezoresponse force microscopy research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. C.S. and J-P.M. were also supported by ARO W911NF-24-1-0010 to fabricate oxide, nitride and mixed ferroelectric heterostructures and establish proximity ferroelectricity, particularly for large thickness values and for epitaxial embodiments, particularly in the context of optical embodiments. R.J.S. acknowledges support from the National Science Foundation Graduate Research Fellowship Program under grant no. DGE1255832. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. J.N. acknowledges support from the Department of Defense through the National Defense Science and Engineering Graduate Fellowship Program. D.B. and A.M.R. acknowledge computational support provided by the National Energy Research Scientific Computing Center (NERSC). We acknowledge using the Penn State Materials Characterization Lab and the Nanofabrication Lab. E.C.D. and S.C. acknowledge the use of the Materials Characterization Facility at Carnegie Mellon University supported by grant MCF-677785. The proximity ferroelectricity phenomenon was conceptualized, developed, initially demonstrated and validated with the support of the Center for 3D Ferroelectric Microelectronics (3DFeM), an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences Energy Frontier Research Centers program under award DE-SC0021118. Piezoresponse force microscopy research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. C.S. and J-P.M. were also supported by ARO W911NF-24-1-0010 to fabricate oxide, nitride and mixed ferroelectric heterostructures and establish proximity ferroelectricity, particularly for large thickness values and for epitaxial embodiments, particularly in the context of optical embodiments. R.J.S. acknowledges support from the National Science Foundation Graduate Research Fellowship Program under grant no. DGE1255832. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. J.N. acknowledges support from the Department of Defense through the National Defense Science and Engineering Graduate Fellowship Program. D.B. and A.M.R. acknowledge computational support provided by the National Energy Research Scientific Computing Center (NERSC). We acknowledge using the Penn State Materials Characterization Lab and the Nanofabrication Lab. E.C.D. and S.C. acknowledge the use of the Materials Characterization Facility at Carnegie Mellon University supported by grant MCF-677785.