Fabrication Of Copper Oxide Films And The Related Optoelectronic Synaptic Performance

Human beings interact with the outside world by perceiving and responding to external stimuli,and 80%of the information comes from the visual system.Therefore,the development of visual bionic system is of great significance to the development of artificial intelligence field.However,the current visual bionic system mainly uses CMOS circuit and von Neumann architecture,which leads to the limits in low efficiency and high power consumption.Therefore,it is necessary to construct optoelectronic synaptic devices based on memristor for visual bionics,so that it can play its due role in the compact artificial intelligence system by integrating neural morphological calculation and visual sensory nerve function.In this dissertation,the transition metal oxide CuO_x was used as the functional layer,the synaptic devices structured as ITO/CuO_x/ITO and ITO/CuO_x/Pt as well as ITO/Ti O_x/CuO_x/Pt were constructed and fabricated respectively.The photoelectric response characteristics and some typical synaptic behaviors of the devices were investigated.Finally,the optoelectronic synaptic devices of ITO/Ti O_x/CuO_x/Pt with excellent performance were successfully realized.The main results are as follows:1.CuO_x thin films(x=1.94～2.56)were deposited by magnetron sputtering method.With the increase of annealing temperature,the surface uniformity and compactness of the film were gradually deteriorated.At a moderate annealing temperature,the film has better spectral absorption characteristics,and the quality of CuO_x film is improved when using Pt as the bottom electrodes.2.Using CuO_x thin film as the functional layer,two types of optoelectronic synaptic devices were constructed and fabricated as ITO/CuO_x/ITO and ITO/CuO_x/Pt,respectively.The effects of electrode structure and functional layer thickness on the photoelectric response characteristics of the devices,and the effects of different oxygen/argon ratio as well as annealing temperature were investigated.When the thickness of the film is 675nm,the oxygen/argon ratio is 1:26,and the annealing temperature is 200℃,the ITO/CuO_x/Pt optoelectronic synapse device exhibits the maximum photoresponse current and the longest relaxation time,successfully simulating the short-term and long-term plasticities of biological synapses.However,there are some shortcomings such as fast photocurrent decay,large noise signal,and poor device stability.3.On the basis of ITO/CuO_x/Pt,a thin TiO_x film was introduced as the second functional layer to prepare the dual-functional layer optoelectronic synaptic devices of ITO/Ti O_x/CuO_x/Pt.The introduction of Ti O_x film and the formation of p-n heterojunction at the interface of Ti O_x/CuO_x could further optimize the performance of the devices,demonstrating a better performance of the devices with lower noise,higher response photocurrent,longer memory time and wider response band.4.Based on the ITO/TiO_x/CuO_x/Pt dual-layer optoelectronic synaptic devices,the short-term plasticity(STP),long-term plasticity(LTP),learning experience and the ablity to sense incident direction were successfully simulated,respectively.In addition,based on the devices two artificial synaptic arrays of 3x5 and 3x3 are constructed successfully,and the synaptic functions of image perception,memory and iris effect have been successfully simulated.