Multilevel resistance switching of individual Cu2S nanowires with inert electrodes

Owing to the enormous demand for data storage and its self-powering potential, resistive random access memory (ReRAM) devices have received much attention. Multilevel memory is advantageous in terms of efficiency and energy saving. In the present work, multilevel resistance has been demonstrated for devices based on individual Cu2S nanowires with two inert (W) electrodes. Up to five levels can be achieved, significantly enhancing the data storage density, by varying the compliance current (C.C.). Compared to previous works on multilevel memory, the present devices exhibit outstanding performances with lower operating voltage (V-set <0.6 V at I-C.C.= 1 mu A), higher on/off ratio (>10(5)) and longer retention time (>10(3) min). From in-situ scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis, the resistive switching (RS) behavior of Cu2S nanowires under high C.C. ( > 1 mu A) was found to be dominated by Cu ion diffusion inside the Cu2S nanowire. On the other hand, holes and vacant Cu lattice sites control the RS under low C.C. (<800 nA). The results of temperature-dependent measurements of resistivity also strongly support the proposed mechanisms. The facile fabrication of Cu2S nanowires with the capability of multilevel switching shall facilitate the realization of high density memristor applications. (C) 2015 Published by Elsevier Ltd.