Coexistence of synaptic behaviour and negative differential resistance at room temperature in the resistive switching device based on natural indigo molecules

Investigation of the transient photo-response and switching window of an Al/indigo/Al device: unveiling negative photoconductivity and the photo-enhanced memory window

“…The non-pinching of I – V characteristics, NDR and the scan rate dependency of NDR has been explained in our previous work on the Al/indigo/Al device. 50 Up to 1.64 V the current increases with bias voltage due to ohmic conduction. After that a reduction in current can be seen where Poole–Frenkel emission happens.…”

“…In the case of indigo molecules, the HOMO–LUMO gap is 1.9 eV obtained via UV-vis spectroscopy. 50 This means that the resonant excitation takes place when the photon energy exactly matches with the optical energy gap. When the photon energy is more than the optical energy gap, the absorption process generates hot electrons and they can thermally relax to the LUMO edge via electron–electron scattering or electron–phonon scattering, generally termed as thermalisation.…”

“…49 In our previous work, it is established that indigo has a 1.9 eV optical bandgap and exhibits neuromorphic properties including learning and forgetting. 50…”