Fabrication Of SnO₂ Film And The Related Optoelectronic Synaptic Performance

In the structure of the traditional von-Neumann computing system,because of the storage and computation components are separated,there is a problem of low data processing efficiency,which cannot meet the requirements of computer performance in the era of big data.The structure of neuromorphic vision system,however,integrates the storage,perception and computation inside the computer and so can improve the efficiency of data processing.The optoelectronic synaptic device composites the functions of photoelectric detection and synaptic plasticity and so can act as the basis of hardware implementation of neuromorphic vision system,which opens a new way to build a neuromorphic vision system with low latency,high response and high stability.In this dissertation,SnO₂ and SnO_x films were prepared by hydrothermal and magnetron sputtering methods,respectively.Based on the comparative testing and quality evaluation of the two films,the functional films and devices were finally produced by magnetron sputtering,and then the optoelectronic synaptic properties of the fabricated devices have been investigated.Based on the research of ITO/SnO_x:Ag/ITO synaptic devices,the ITO/HfO_y/SnO_x:Ag/ITO devices have been investigated and shown outmuch better performance with low noise,high response photocurrent and stable functionalization.The main results are as follows:（1）Crystalline SnO₂ films were fabricated by hydrothermal method.Through the characterizationof the composition,surface morphology and crystalline state,the polycrystalline films with nanoflower structure were successfully produced.The photodetector made from this kind of SnO₂ demonstrates obvious photoelectric response effect,however,theycould not be used as synaptic devices.（2）High-quality SnO_x films and ITO/SnO_x/ITO as well as ITO/SnO_x:Ag/ITO monofunctional layer optoelectronic synaptic devices were successfully fabricated by magnetronsputtering or co-sputtering.It is shown that the ITO/SnO_x:Ag/ITO devices could generate larger photocurrents and simulate many functions of biological synapses such as STP,LTP and SRDP.However,the devices still have the limits of fast decay of photocurrent with high noise and unstable performance when the light is switched off.（3）Based on the ITO/SnO_x:Ag/ITO optoelectronic synaptic device,the ITO/HfO_y/SnO_x:Ag/ITO bilayer synaptic device was fabricated by introducing thin HfO_yfilm as the second functional layer.It is shown that the testing device has even larger response photocurrent,wider response wavelength range and better memory ability,and so could simulate many functions of biological synapses such as STP,LTP,SRDP,and learning experience with a good operating stability.