Large Resistive Switching in Ferroelectric BiFeO₃ Nano‐Island Based Switchable Diodes

Abstract

The demand for non-volatile memory technologies that offer high speed, high storage density and low power consumption has stimulated extensive research into new functional materials and device physics. [1][2][3][4][5] Nano-ferronic devices based on multiferroic/ferroelectric materials have been emerging as nextgeneration nano-electronics, which deal with the interplay between ferroic orders (e.g. ferroelectricity and ferromagnetism) and electronic transport on the nanoscale. [ 6 ] Recent investigations into various multiferroic/ferroelectric materials have revealed remarkable polarization dependent electronic transport properties, which include signifi cant electroresistance effects in a switchable ferroelectric diode [7][8][9][10][11] and multiferroic/ferroelectric tunnel junctions (M/FTJs) [12][13][14][15][16][17] and intriguing charge conduction in ferroelectric domain/walls. [ 18 , 19 ] These conduction properties can be utilized for fast and non-destructive readout in emergent non-volatile memories such as resistive random access memory (RRAM) and memristor. [ 20 ] Especially, ferroelectric-resistive memories based on ferroelectric diode and tunnel junctions have demonstrated that it is possible to achieve high resistive ON/OFF ratio, high speed and low write power with a high reproducibility by controlling ferroelectric polarization. In a switchable ferroelectric diode, the Schottky-to-Ohmic contacts, forming at the interfaces between metal electrodes and semiconducting ferroelectric thin fi lms, are reversibly modulated by the polarization fl ipping which gives rise to rectifi cation direction switching . [8][9][10][11] The tunnel junctions with ultrathin ferroelectric barrier yield a giant tunnel electroresistance effect resulting from the change of asymmetric tunnel barrier heights controlled by ferroelectric polarization direction. However, multiferroic/ferroelectric nano-structures such as nano-islands and nano-wires have not yet been exploited for ferroelectric-resistive memories, although large storage capacity, lower power consumption and high reliability are expected for such nano-structures. They also provide an effective way to understand and manipulate the ferroelectric-resistive switching, piezoelectricity, polarization and domain structures on the nanoscale. On the other hand, the fabrication of ferroelectric nano-structures through bottom-up approach is crucial to realizing high-performance of nano-ferronic devices since top-down approach may induce serious deterioration in ferroelectric nano-structures. [ 21 , 22 ] Here, we explored the local charge conductions and their coupling with ferroelectric polarization in highly oriented ferroelectric BiFeO 3 (BFO) nano-islands array by using conductive atomic force microscopy (CAFM) and piezoresponse force microscopy (PFM). We observed a switchable diode effect in BFO nano-islands grown on SrRuO 3 /SrTiO 3 (SRO/STO) substrate, which showed the direct correlation between rectifi cation and ferroelectric polarization directions. The rectifi cation...

Recent Progress in Ferroelectric Diodes: Explorations in Switchable Diode Effect

“…However, many recent investigations have demonstrated a dominant role played by the ferroelectric polarization in switchable diode effect [26][27][28][29]. Jiang et al confirmed that the resistive switching curves of the SRO/BFO/Pt structure have identical shapes to the Polarzation-Voltage loops.…”

“…Since then many similar phenomena have been observed in various ferroelectric thin films [15][16][17][18][19]. Most interestingly, the switchable diode effect has been demonstrated recently in various ferroelectric structures ranging from organic films [20,21], inorganic bulks [22][23][24], and inorganic films [25][26][27][28][29]. The switchable diode effect means that the polarity of the diode can be reproducibly switched by the reversion of the applied electric field in the MFM structures, due to the polarization modulated barrier.…”

“…The switch-ability between the reverse and forward diodes originates from the band modification and associated change in the barriers at the BFO/metal interfaces, which depends on the ferroelectric polarization direction. By using Conductive-AFM and PFM techniques, Hong et al observed a switchable diode effect induced by the ferroelectric polarization in BFO nano-islands [29]. In short, most of recent experiments have proved that the polarization dominates the switchable diode effect in ferroelectric diodes.…”

“…Up to now, the research on the switchable diode effect is mainly focused on BiFeO 3 (BFO) materials [22,[25][26][27][28][29]. In most cases, the BFO thin films were grown on the bottom electrode covered SrTiO 3 substrates by pulsed laser deposition, and then the top electrodes were deposited on the BFO films to form MFM structures.…”

Correlation between electrospinning parameters and magnetic properties of BiFeO3 nanofibers

“…It has been widely studied due to its potential use for information storage applications [2,3] and low band gap; thus, its ferroelectric [4][5][6][7], ferromagnetic [8][9][10][11] and photovoltaic [12][13][14] properties have been analyzed. The BiFeO 3 perovskite is particularly interesting because having ferroelectric and ferromagnetic properties, it can display magneto-electric coupling, that is, the capacity to control electrical polarization by application of a magnetic field and control magnetism by the application of an electric field [3,15].…”