“…According to the way the current increases, memristors can be roughly classified as digital or analog. The characteristic feature of a digital memristor is that resistive switching is abrupt, and it has been widely studied for its simple structure, easy three-dimensional stacking, and fast resistive switching speed [ 13 , 14 , 15 , 16 , 17 , 18 ]. For the last few years, analog memristors are typically characterized by gradual resistive switching, which has attracted more and more attention due to the application value of brain-like morphology calculations [ 19 , 20 ], programmable analog circuits [ 21 ], and the like.…”