Evolution of resistive switching polarity in Au/Ar+ bombarded SrTi0.993Nb0.007O3/In sandwiches

Abstract

We investigated the resistive switching characteristics of Au/Ar + bombarded SrTi 0.993 Nb 0.007 O 3 /In sandwiches. The evolution of the resistive switching polarity with sweeping voltage was observed. Our experiments showed that under a macroscopic electrode the homogeneous trapping-detrapping-type conduction and filament-type conduction coexist and compete with each other. For a large sweeping voltage range, the trapping-detrapping-type conduction dominates. However, for a small range the latter dominates. If the bias voltage is too large, the filament conduction could be destroyed. These results will help deepen the understanding of the resistive switching polarity, and will aid in future device design. bipolar resistance switching, I-V curves, switching polarityBecause of the increasing demand for miniaturization in microelectronics, nonvolatile resistance random access memory (RRAM) based on sandwich unit cells composed of metal/transition metal oxide (TMO)/metal has attracted considerable attention in the past few years [1-6]. The cell resistance can be switched between different levels using an applied voltage. In a bipolar switching system, the low and high resistance states (LRS, HRS) are set and reset by the different polarity of the applied voltage. Two basic switching models have been proposed. One is the filament conduction model [4,[6][7][8][9], and the other is the homogeneous Schottky-type switching model [5,10,11]. Note that the two switching mechanisms result in different switching polarities. For n-type semiconductors and a voltage sweeping sequence of 0 VV + 0 V V   0 (here V + and V  are the maximum positive and negative applied voltages, respectively), the filament conduction model predicts that the resistance will change from a LRS to a HRS for a positive voltage, and vice versa for a negative voltage. Therefore, a "Counter- Figure-8" hysteretic current-voltage (I-V) curve is observed. However, the Schottky-type switching model changes the resistance from a HRS to a LRS for a positive bias, and vice versa for a negative bias, resulting in a "Figure-8" hysteretic I-V curve. Nb-doped SrTiO 3 (NSTO) single crystal is commonly used as a conductive substrate for functional perovskite oxide thin films. Its resistive switching characteristics have been intensively investigated [5,[11][12][13]. To the best of our knowledge, only " Figure-8" I-V curves have been reported. Recently, both "Figure-8" and "Counter-Figure-8" I-V curves were observed simultaneously in thick defective Sr 2 TiO 4 [14]and Fe-doped SrTiO 3 (STO) films [15]. However, the dynamic evolution process was not detailed in the reports.It is widely accepted that after forming process, bipolar resistive switching occurs at the active metal/TMO interface [16,17]. Therefore, we believe that by modifying the active interface we can control the bipolar resistive switching properties. In this work, we modified the NSTO surface via