| With the rapid development of science and technology in modern society,the traditional computer system is getting closer to a performance bottleneck,and the biological neural network and artificial intelligence have drawn much more attention nowadays.Synapse is an important part of neural network,and memristor is similar to biological synapse in terms of the structure and the function.Therefore,memristor is the most suitable device for making bionic synapse.In this thesis,several memristors made of SiOx/TiOx or SrTiOx/SiOx dual dielectric thin films have been fabricated through magnetron sputtering and photolithography processes.The resistive switching performance and the electronic conductive mechanism as well as working mechanism of these memristor devices have been studied systematically and deeply.Moreover,based on the enhanced analog resistive switchingperformanceof bothPt-Ag/SiOx:Ag/TiOx/p++-Siand Pt-Ag/SrTiOx:Ag/SiOx/p++-Si memristor devices,many diverse synaptic functions and memory abilities have also been investigated extensively.The main results of this thesis are as follows:?1?The Pt-Ag/SiOx/p++-Si memristor is a kind of non-volatile resistive switching device.After 43 cycles of programming,the switch ratio of the device is reduced to 1,and the repetitive stability is not so high.The Pt-Ag/SiOx:Ag/p++-Si memristor is also a kind of non-volatile analog resistive switching device,but the range of resistance modulation is limited and the reliability is not high enough.?2?However,the memristor modified as Pt-Ag/SiOx:Ag/TiOx/p++-Si works repeatedly and stably,and its switch ratio is as high as 102.It has been realized that this memristor device can be used as an analog resistive switch and the device resistance could be continuously modulated in a large range.The modified Pt-Ag/SiOx:Ag/TiOx/p++-Si memristors can be used as biomimetic synapses,and multiple synaptic functions have been successfully demonstrated,such as paired-pulse facilitation,long-term/short-term plasticity,multi-level memory,etc.?3?The Pt-Ag/SrTiOx/n++-Si device is a kind of volatile memristor,but it works very unstable and so can not be used as a resistive switch directly.The Pt-Ag/SrTiOx/p++-Si device is a kind of non-volatile memristor with a typical forming process.After the forming process,the set and reset processes are getting slower and then the device exhibits the characteristics of analog resistive switching behaviour.It is noted that there is no forming process in the Pt-Ag/SrTiOx:Ag/p++-Si memristor,and the conductivity values can be continuously modulated between 2×10-6S and 1×10-4S,demonstrating an analog resistive switching behaviour.?4?The most important is that a switch ratio of as high as 102 and a longer stable repeatedly working cycles of 5×103 have been achieved in the modified Pt-Ag/SrTiOx:Ag/SiOx/p++-Si memristor,representing a much better continuously conductance modulation between 2×10-6S and 1×10-3S,and therefore a good analog switch with an enhanced resistive switching performance.The modified Pt-Ag/SrTiOx:Ag/SiOx/p++-Si memristors can also be used as biomimetic synapses,and multiple synaptic functions have been successfully realized,such as long-term/short-term plasticity,multi-level memory,pulse spike rate dependent plasticity,etc. |
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