Resistive switching characteristics and set-voltage dependence of low-resistance state in sputter-deposited SrZrO3:Cr memory films

Abstract

60 - nm -thick Cr-doped SrZrO3 thin films with polycrystalline structure were fabricated on SrRuO3∕SrTiO3 (100) substrates at 450°C by off-axis radio-frequency sputtering. From room temperature current-voltage measurements of Pt∕Cr-doped SrZrO3∕SrRuO3 structures, reproducible bistable resistive switching behavior was observed. The dominant conduction mechanisms of the high-resistance state were Ohmic conduction in the low-electric-field region and Frenkel-Poole emission in the high-electric-field region, while the low-resistance state fully followed Ohmic conduction. These bulk-limited conduction mechanisms imply that resistive switching phenomena may be related to the conducting path in the SrZrO3:Cr film matrix. In addition, the initial-resistance value of as-deposited SrZrO3:Cr films was much higher than that of the high-resistance state, indicating that the first soft-breakdown behavior (defined as the resistance change from the initial-resistance state of as-deposited film to the low-resistance state) is the forming process which generates the conducting path in the SrZrO3:Cr film matrix. As the set voltage (=switching voltage from the high- to low-resistance state) was increased, both the low-resistance state current and the reset voltage (=switching voltage from the low- to high-resistance state) increased due to the generation of a stronger or higher-density conducting path. We suggest that the mechanism of resistive switching is related to the formation of the conducting path in the SrZrO3:Cr matrix, and that the on-state current is determined by the set voltage which controls the generation of the conducting path.