Transition between resistive switching modes in asymmetric HfO2-based structures

Abstract

We claim that the evolution of conductive filaments (CF) in bipolar resistive switching (BRS) and complementary resistive switching (CRS) is similar in HfO2-based structures with one active layer. The difference in the observed I-V characteristics is explained by the presence of a non-Ohmic contact at the interface with the injection electrode, with the higher barrier at the BRS. In order to describe the transition between BRS and CRS in the asymmetric structure, we form Pt/HfO2(2 nm)/HfOXNY (4 nm)/TiN structure. The active layer of the structure and part of the active electrode were formed via plasma-enhanced atomic layer deposition. Top Pt-electrode was formed via sputtering throughout a shadow mask and area of top electrodes was equal to 0.0360 ± 0.0015 mm2. Pulse and DC measurements of I-V characteristics were carried out. A self-compliance RS with a current lower than 10 mA was found. The primary conduction mechanism in the low-resistance state for both RS modes was estimated as space-charge limited current (SCLC). For BRS, the unusual transition from trap-limited conduction to charge-carrier saturation (I ∼ V1.14) is found to be at 0.35 V in positive bias polarity. Charge-carrier saturation was not found at negative bias polarity. We attribute this to the higher injection barrier on the active electrode side (TiN). We attribute the increase in the barrier height to the accumulation of positive vacancies near the electrode interface.