Identify the active interface defect responsible for wavelength-selective plasticity

Identify the active defect at the buried Se/ZnMgO interface responsible for the persistent photoconductance and wavelength-selective potentiation and depression by performing spectroscopic measurements of the buried interface.

Background

The paper attributes the synaptic behavior to charge-state transitions of defects near the Se/ZnMgO interface, with oxygen vacancies proposed as the most plausible candidate based on defect physics in ZnO-family materials. The proposed mechanism is that ultraviolet illumination fills ionized interface defects with photogenerated electrons, whereas lower-energy illumination photoionizes neutral defects and erases the potentiated state.

The authors explicitly state that the oxygen-vacancy identification remains hypothetical. They explain that the measured crossover photon energy reflects the balance between competing processes rather than a single defect transition, and that direct identification requires spectroscopic characterization of the buried interface, which was outside the scope of the reported work.

References

The identification of the vacancy as the active defect relies on the defect physics of the ZnO family and it is still just a hypothesis at this point. The crossover energy measured here (2.45 to 3.4 eV depending on the batch) characterises the balance of the two processes rather than a single transition, and for a direct identification, it would require spectroscopic measurements of the buried interface, and this is beyond the scope of this work.

— Wavelength-selective bidirectional plasticity in self-powered Se/ZnMgO visual synapses  (2610.21618 - Li-Kao et al., 15 Oct 2026) in Section 3.2, paragraph beginning “The identification of the vacancy as the active defect”