Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The resistive switching (RS) of functional oxide thin films has attracted tremendous interest recently due to its promising application as building blocks in non-volatile memory devices. [1] By applying voltage pulses, the functional oxide films are switched between different resistance states and may store information, which is the basis of resistance random access memory (RRAM). However, the RS performance of the oxides still needs improvement for a future commercial application, and the physical mechanism of the RS is not fully understood yet. The point defects, especially oxygen vacancies, play an important role on determining the electrical conduction of oxide thin films. [2] This work reports a low cost and effective approach to tune the resistive switching behavior of BiFeO3 films which have been deposited by pulsed laser deposition [3] and irradiated with low energy Ar+ ions. Due to the preferential sputtering of BiFeO3 films, oxygen vacancies as well as the surface morphology can be tuned by low energy irradiation in a controllable way to enhance the RS performance. The obvious improvement of key switching parameters, i.e. the resistance stability and retention, was observed in the irradiated BiFeO3 (Figure 1). These improvements give an opportunity to design a nonvolatile memory with a multilevel RS function which is more scalable than a memory based on bistable RS reported by most of studies [3]. The changing of the conduction mechanism in the BiFeO3 from Poole-Frenkel to space-charged-limited conduction after irradiation will be discussed. The combination of the microstructure analysis and the electrical characterization of the irradiated BiFeO3 will gain an insight into the resistive switching mechanism.

Figure 1(a) I-V characteristic curves showing a significant improvement of the stability of resistive switching in BiFeO3 film after irradiation. The distinguishable neighboring resistance states in the irradiated sample allow for designing multilevel RS memory devices based on BiFeO3 films. (b) Retention test showing the nonvolatile resistance states in irradiated BiFeO3 film on an extrapolated time scale of 10 years.

[1] R. Waser et al., Nature Materials 6, (2007) 833.
[2] D. W. Reagor et al., Nature Materials 4, (2005) 593.
[3] Y. Shuai et al., Applied Physics Letters 98, (2011) 232901.
[4] Y. Shuai X. Ou et al., Journal of Applied Physics 111, (2012) 07D906.