Construction Of Optoelectronic Memristor Based On TiO₂ Materials And Emulation Of Neuromorphic Visual Functions

Emulating human visual system is a feasible strategy to realize efficient image perception,which is the research hotpot in artificial intelligence field.Traditional machine vision is faced with challenging problems including high power consumption,data redundancy,speed delay due to the separated hardware structure of sensing memory and computing unit.Optoelectronic memristive device,as emerging multifunctional nanodevice,combines the characteristics of neuromorphic computing and optically modulation,which is considered as promising candidate to construct novel neuromorphic visual system.However,optoelectronic memristor is still in the preliminary development stage.Several critical problems hinder the subsequent development of neuromorphic visual system,such as low conductance linearity,limited response spectrum and complicated modulation methods.In this work,several TiO₂-based optoelectronic memristive devices are developed through nanocomposite materials construction and device structure design.The emulation of neuromorphic visual functions has also been implemented based on the unique optoelectronic memristive behaviors.The details are as follows:1.TiO₂-based charge trapping/detrapping optoelectronic memristor.At the present stage,oxide-based optoelectronic memristor suffers from low conductance linearity,limited response spectrum,which seriously affects the overall performance of neuromorphic visual system.In order to solve the above problems,we have conducted the following targeted investigations:（i）TiO₂/Hf O_xheterojunction optoelectronic memristor is constructed.Herein,multiple non-volatile state and high conductance linearity（Nonlinearity=0.428）have been realized ultilizing the trapping of photogenerated holes at defect level of Hf O_xlayer.The reversible control of device conductance has also been achieved with the synergistic modulation of optical and electrical signals,i.e.,optical set and electrical reset behaviors.Besides that,several basic synaptic functions have been emulated under the action of ultraviolet pulse,including excitatory postsynaptic current and learning-experience behavior.Furthermore,we constructed high-performance neuromorphic visual system with the recognition rate of 96.7%,which is 40%higher than the system comprising of pure TiO₂-based device;（ii）optoelectronic memristor with broadband spectral response was constructed with TiO₂nanowire and graphene quantum dots grown by hydrothermal technique.Various response amplitude and synaptic plasticity can be realized under the illumination of blue（450 nm）,green（543 nm）and red（622 nm）light.Based on that,the perception of color-mixed image and emulation of Pavlov dog experiment are realized with combined multi-wavelength optical signals.2.TiO₂-based plasmonic optoelectronic memristor.A novel plasmonic optoelectronic memristor based on Ag-TiO₂nanocomposite film is constructed by introducing Localized Surface Plasmon Resonance effect.Long-term potentiation and depression behaviors can be realized under the action of visible and ultraviolet light,respectively.The image sensing and pre-processing functions have been demonstrated in 8×8 memristive array.Herein,the pre-processing function mainly consists of contrast enhancement and noise depression,which can effectively highlight the feature information and reduce data redundancy.Furthermore,the light-gated and electrically driven memristive behaviors can also be performed in the same device with the photo-induced oxidation/reduction of silver nanoparticles.Thereby,the plasmonic optoelectronic memristive array integrates the functionalities of image sensing,low-level pre-processing and high-level processing.Beneficial from the low-level pre-processing,the overall recognition rate is up to 98%.3.TiO₂-based conformable optoelectronic memristor.in this chapter,we develop Ag-TiO₂nanostructured particles and constructed hemispherical plasmonic memristive array to simulate human retina.As functional unit,Ag-TiO₂nanostructured particles is the foundation to realize all-optically modulation.Meanwhile,Sodium alginate is selected as base material to provide mechanical flexibility.Several basic logic operation and random image encryption/decryption function have been implemented with all-optical modulation characteristics.A 30×30 conformable memristive array is constructed to realize angle detection,utilizing angle-dependent characteristics of device unit.Furthermore,Stereoscopic perception function is performed with two independent memristive arrays simulating the binocular vision effect.Finally,the memristive mechanism model is investigated with TEM and KPFM tecchinique.The above hemispherical all-optically controlled device provides promising hardware choice for the bionic emulation of complicated visual functions.