| Since silicon-based amorphous thin-films such as a-Si,a-SiO_x,a-SiN_x,and a-SiO_xN_y have diverse refractive indices and extinction coefficients in a relatively wide spectral range,the study of these thin-films is of great significance.By studying well into the combination of these different multilayers with their better optical properties,and properly controlling of the refractive indices or extinction coefficient between the film systems,it is thus possible to apply these silicon-based amorphous thin-films to the silicon-based memristors in the near future.In this paper,non-stoichiometric amorphous silicon nitride films as a-SiN_x and metal-doped amorphous silicon nitride films as a-SiN_x:Ag(Cu)were fabricated by magnetron co-sputtering method.The influence of N/Si ratios and metal doping have been studied on the microstructure and optoelectronic properties of the two amorphous silicon nitride films by multiple characterization methods.By combining photolithography process and magnetron sputtering method,three different memristors taking a-SiN_x as the memristive dielectric material were fabricated,and the electrical switching performance of the memristors have been studied.The main results are as follows:(1)With the increase of N content,the number of Si-N bonds in the a-SiN_x films is increased,and that both the short-range order and the medium-range order of amorphous network is decreased with also the increased internal defects in the a-SiN_x films.In the visible light range,with the increase of N content,the refractive index and extinction coefficient of the a-SiN_x films are both decreased,and the transmissivity as a whole is gradually increased,but the absorptivity as a whole is gradually decreased.In the near-infrared light range,the transmissivity of the a-SiN_x thin films is gradually decreased with the nitrogen flow rate from 0 sccm to 1 sccm.The overall transmissivity of the a-SiN_x films is,however,gradually decreased while the nitrogen flow rate continues to increase from 1 sccm to 5 sccm.The absorptivity of a-Si films is higher than that of a-SiN_x films in near infrared range,but the absorptivity disperse caused by different N content in a-SiN_x films is still not obvious.(2)With the increase of metal doping concentration,the short-range order of the amorphous network structure is decreased but the medium-range order is increased,while the internal defects of the films is decreased;Due to the exist of metal atoms,the defects in the a-SiN_x:Metal thin films are increased and the effect of N atoms on the vibration of Si-Si bonds is weakened,leading to the frequency shift of the TO modes.With the increase of metal doping concentration,the absorption of surface plasmon resonance is enhanced,resulting in the increase in refractive index and extinction coefficient of the a-SiN_x:Ag(Cu)films.And in the visible and near infrared light range,the transmissivity of the a-SiN_x:Ag(Cu)films show a decreasing trend but the absorptivity show an increasing trend.With the increase of metal doping concentration,the resistivity of the a-SiN_x:Ag(Cu)film decreases by 7-9 orders of magnitude,indicating that the metal doping can effectively improve the conductivity of the a-SiN_x:Metal films.(3)Three prototype memristors of Ag/a-SiN_x/Al,Ag/a-SiN_x/ITO and Cu/a-SiN_x/ITO have been constructed and fabricated,and the electrical switching function of these three memristors has been realized.The preliminary results show that the performance of the memristor based on a-Si N_x film is affected by the compliance current,the size of the top electrode,and the material of the electrode. |
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