Optoelectronic Synapse Devices Based On SrTiO₃ Thin Films

Artificial vision bionic systems can enable intelligent devices such as robots and autopilots to acquire information from the external environment independently as humans do.However,the vision bionic systems composed of the image sensors and von Neumann structure computer not only produce a large amount of redundant data but also face the von Neumann bottleneck.Therefore,developing a new generation of artificial vision bionic systems is highly required.Optoelectronic synapse devices have the functions of sensing,memorizing and processing optical information.It is considered to be the most promising candidate for the new generation of visually intelligent bionic systems.This thesis takes perovskite oxide SrTiO₃as the research object.Two kinds of optoelectronic synapse devices structured as ITO/SrTiO_x/ITO and ITO/SrTiO_x:Ag/ITO based on the single functional layer of SrTiO_x and SrTiO_x:Ag,were constructed and fabricated,and then their optoelectronic properties and synaptic properties were studied.Furthermore,by introducing a second functional layer into the structure of ITO/SrTiO_x:Ag/ITO,a modified device structured as ITO/SrTiO_x:Ag/CuAlO_x/ITO was constructed and fabricated,and the optoelectronic response characteristics and synaptic performance were deeply studied.The main contents of this thesis are as follows.1.The composition,surface morphology and optical properties of the fabricated SrTiO_xfilm and SrTiO_x:Ag film were characterized.It is found that the thickness of SrTiO_x film would affect its absorptivity,and the absorptivity is positively correlated with the thickness.When sputtering,the larger the argon oxygen ratio in the vacuum cavity,the more oxygen vacancy defects in the film.The metallic Ag exists in the form of single-crystal nanoparticles inside the SrTiO_x:Ag film,and the alloying content of Ag has a significant effect on the spectral absorbance of the film.2.Two kinds of optoelectronic synapse devices,ITO/SrTiO_x/ITO and ITO/SrTiO_x:Ag/ITO,were successfully fabricated,and the influence of the parameters of the functional layers on the optoelectronic properties of the synaptic devices was studied.When the thickness of the SrTiO_x film is 70 nm,the working gas argon-oxygen ratio is53:1,and the metal Ag content is 7.2%,the response photocurrent of the corresponding synaptic device is the largest,and the response wavelength range is the widest.The device can successfully simulate the short-term plasticity and long-term plasticity of synapses,while having the disadvantages of fast decay of persistent photocurrent,high dark current and large noise.3.A modified optoelectronic synapse device structured as ITO/SrTiO_x:Ag/CuAlO_x/ITO was successfully fabricated.Compared with the device of ITO/SrTiO_x:Ag/ITO,it is found that the improved optoelectronic synapse device based on the dual-functional layers has the characteristics of smaller noise,better memory effect,lower dark current and wider response band.The short-term plasticity,long-term plasticity and learning experience of the ITO/SrTiO_x:Ag/CuAlO_x/ITO optoelectronic synapse device were intensively tested and studied.Based the above individual devices,a 3?3 array was combined,and the perception,memory and noise reduction functions of the image have been simulated successfully.