Role of metal-oxide interfaces in the multiple resistance switching regimes of Pt/HfO2/TiN devices

The multiple resistive switching of Pt/HfO2/TiN devices is demonstrated as a result of a competition between the switching at opposite metal/oxide interfaces. Three switching operation modes are demonstrated: clockwise (CW) switching (set for negative voltage and reset for positive voltage at Pt electrode), as already reported in literature for similar material stacks; counterclockwise (CCW) switching and complementary switching (CS) that consist in a set and a reset for increasing voltage of the same polarity. The multiple switching operation modes are enabled by a deep-reset operation that brings the cell resistance close to the initial one. As a consequence, the set transition after a deep-reset occurs at the same voltage and currents as those of the forming and leads to a low resistance state whose resistance can be further decreased in a CCW switching or increased back with a CW switching. With a suitable choice of the stop voltage, a CS in obtained, as well. The coexistence of all three CW, CCW, and CS operations demonstrates that both metal-oxide interfaces are active in the formation and the dissolution of conductive filaments responsible for the switching. All these observations are discussed in terms of a competition between ion migration processes occurring at the opposite metal-oxide interfaces. (C) 2015 AIP Publishing LLC.