Non–zero-crossing current-voltage hysteresis behavior in memristive system

Since the memristor was theoretically predicted at 1971, the research on memristor and memristive behavior has attracted great interest. However, there is a debate about the physical model of the non–zero-crossing (or named non-pinched) current-voltage (I–V) hysteresis behavior observed experimentally in many reported memristive devices. By identifying and analyzing all these non–zero-crossing hysteresis curves, we attribute this behavior to three mechanisms: the involvement of a capacitive effect, the appearance of a ferroelectric or piezoelectric polarization, and the formation of an internal electromotive force. Among them, the memristive behavior involving a capacitive effect has been reported extensively. It demonstrates that the combination of multiple physical properties (memristive and capacitive) in a single device could prefigure potential multifunctional applications. In this review, we discuss the physical mechanism of non–zero-crossing I–V curves, the related research progress with particular emphasis on the origin of non–zero-crossing I–V curves. Moreover, the existing problems in this field and the possible solutions will be discussed, providing an outlook for the future developments.