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Abstract The emergence of memristive behavior in amorphous–crystalline 2D oxide heterostructures, which are synthesized by atomic layer deposition (ALD) of a few‐nanometer amorphous Al2O3layers onto atomically thin single‐crystalline ZnO nanosheets, is demonstrated. The conduction mechanism is identified based on classic oxygen vacancy conductive channels. ZnO nanosheets provide a 2D host for oxygen vacancies, while the amorphous Al2O3facilitates the generation and stabilization of the oxygen vacancies. The conduction mechanism in the high‐resistance state follows Poole–Frenkel emission, and in the the low‐resistance state is fitted by the Mott–Gurney law. From the slope of the fitting curve, the mobility in the low‐resistance state is estimated to be ≈2400 cm2V−1s−1, which is the highest value reported in semiconductor oxides. When annealed at high temperature to eliminate oxygen vacancies, Al is doped into the ZnO nanosheet, and the memristive behavior disappears, further confirming the oxygen vacancies as being responsible for the memristive behavior. The 2D heterointerface offers opportunities for new design of high‐performance memristor devices.
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Persistent photoconductivity in barium titanate
Annealed bulk crystals of barium titanate (BaTiO3) exhibit persistent photoconductivity (PPC) at room temperature. Samples were annealed in a flowing gas of humid argon and hydrogen, with a higher flow rate corresponding to larger PPC. When exposed to sub-bandgap light, a broad infrared (IR) absorption peak appears at 5000 cm−1(2 μm), attributed to polaronic or free-carrier absorption from electrons in the conduction band. Along with the increased IR absorption, electrical resistance is reduced by a factor of approximately two. The threshold photon energy for PPC is 2.9 eV, similar to the case of SrTiO3. This similarity suggests that the mechanisms are similar: an electron in substitutional hydrogen (HO) is photoexcited into the conduction band, causing the proton to leave the oxygen vacancy and attach to a host oxygen atom. The barrier to recover to the ground state is large such that PPC persists at room temperature.
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- Award ID(s):
- 2109334
- PAR ID:
- 10363604
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- Journal of Applied Physics
- Volume:
- 131
- Issue:
- 9
- ISSN:
- 0021-8979
- Page Range / eLocation ID:
- Article No. 095701
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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