Fabrication And Memristive Synaptic Functionalization Of Ru-doped SiO_x Films

The rapid development of artificial intelligence,the Internet of Things,and big data services have made our society pursue better data utilization,high-speed data processing,and computing power in the process of information processing.It is known that the existing serial computing methods have reached their limits,and the emerging memristors are similar in structure and function to biological synapses.High-performance computing can be achieved by building neuromorphic computing systems through memristive artificial synapses.In this thesis,two single-layer memristors based on SiO_x and SiO_x:Ru have been fabricated by the sputtering method,which has analog and forming-free switching characteristics.In addition,two double-layer memristors as Ru/SiO_x:Ru/Ti O_x/p⁺⁺-Si and Ru/SiO_x:Ru/Al O_x/p⁺⁺-Si,were also prepared successfully.Based on the excellent switching performance,several memristive synaptic properties of the two memristive devices have been investigated systematically.The main research results obtained in this thesis are as follows.1.The Ru/SiO_x/p⁺⁺-Si memristive device with a single memristive layer has an obvious forming phenomenon.After completing the forming,it has a slow set and reset process,showing that it is an analog memristor with a switch ratio of about 150.The performance of the device is related to the thickness of the dielectric layer and the oxygen content.The device with a dielectric layer thickness of 30 nm increases the high resistance state current with the increase of the oxygen content.2.Based on the Ru/SiO_x/p⁺⁺-Si memristor,a modified memristor as Ru/SiO_x:Ru/p⁺⁺-Si was obtained by Ru-doping in the SiO_x layer,which could eliminate the forming phenomenon,maintaining a gradual set and reset process,reducing power consumption,improving the working stability of the device,and being able to be controlled under different limited currents.However,Ru-doping will reduce the overall resistance of the dielectric layer and increase the current of the high-resistance state,thereby reducing the on-off ratio of the device.3.Based on the Ru/SiO_x:Ru/p⁺⁺-Si memristor,by inserting Ti O_x as the second dielectric layer,a modified memristor as Ru/SiO_x:Ru/Ti O_x/p⁺⁺-Si was obtained,demonstrating a good analog behavior with good repeatability and significantly improved switching ratio.The device can realize a multi-level enhancement and inhibition round-trip regulation of synaptic weights continuously,and can also realize various synaptic functions such as short-term/long-term plasticity and multi-level memory behavior.4.Based on the Ru/SiO_x:Ru/p⁺⁺-Si memristor,by inserting Al O_x as the second dielectric layer,a modified memristor as Ru/SiO_x:Ru/Al O_x/p⁺⁺-Si was also obtained.It is found that the memristor is also a good analog one with a better on-off ratio of 10~2 and a good switching consistency.The device can also achieve multi-level enhancement and inhibition of synaptic weights,with typical paired-pulse facilitation characteristics,better short/long-term synaptic plasticity,and multi-level memory effects.Moreover,the device also demonstrates many biological synaptic behaviors like pulse amplitude,pulse width,and pulse frequency-dependent plasticities.