Comparison of Interfacial and Bulk Ionic Motion in Analog Memristors

Analog LiNbO₂ memristors are characterized using potentiodynamic electrochemical impedance spectroscopy. It is shown that LiNbO₂-based devices exhibit analog memristive and meminductive or memcapacitive behavior depending on the applied frequency. The impedance spectra are fit to a circuit model whose elements correspond to ionic and electronic effects in the bulk and at the electrode-semiconductor interface. By separating out the bulk and interfacial effects, it is shown that the majority of the ionic movement in the cation-based analog memristor is at the interfaces. It is also shown that ionic capacitance results from a drift field-driven phase shift between the ac bias and the ionic motion, whereas the ionic inductance phase shift results from diffusion relaxation. Thus, to maximize resistance changes due to this ionic movement, analog memristors should be fabricated with negligible bulk dimensions.