Resistive switching in silicon suboxide films
Résumé
We report a study of resistive switching in a silicon-based memristor/resistive RAM (RRAM)
device in which the active layer is silicon-rich silica. The resistive switching phenomenon is an
intrinsic property of the silicon-rich oxide layer and does not depend on the diffusion of metallic
ions to form conductive paths. In contrast to other work in the literature, switching occurs in
ambient conditions, and is not limited to the surface of the active material. We propose a switching
mechanism driven by competing field-driven formation and current-driven destruction of
filamentary conductive pathways. We demonstrate that conduction is dominated by trap assisted
tunneling through noncontinuous conduction paths consisting of silicon nanoinclusions in a highly
nonstoichiometric suboxide phase. We hypothesize that such nanoinclusions nucleate preferentially
at internal grain boundaries in nanostructured films. Switching exhibits the pinched hysteresis I/V
loop characteristic of memristive systems, and on/off resistance ratios of 104:1 or higher can be
easily achieved. Scanning tunneling microscopy suggests that switchable conductive pathways are
10 nm in diameter or smaller. Programming currents can be as low as 2 lA, and transition times
are on the nanosecond scale.
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