Robust unipolar resistive switching of Co nano-dots embedded ZrO2 thin film memories and their switching mechanism

Abstract

The preparation and electrical properties of Ti/Co Embedded (Co-E) ZrO2/Pt resistive switching memories are investigated. The Co nano-dots are formed in ZrO2 thin film after the memory device is annealed at 600 °C in N2 ambient for 60 s without any chemical reaction between Co and ZrO2, which is confirmed from the transmission electron microscopy, energy dispersive X-ray analyzer, and X-ray photoelectron spectroscopy observations. The devices exhibit low forming voltage of −1.5∼−2.8 V and robust negative bias unipolar resistive switching behaviors with small negative set voltage of −1.1∼−1.6 V. A physical model based on a filament mechanism is employed to explain the switching behaviors. It has a high potential for ultra high density nonvolatile memory applications.

Nonpolar resistive switching in Cu/SiC/Au non-volatile resistive memory devices

“…16 Typical I-V characteristics of the stable switching cycles of the Cu/a-SiC/Au devices with 1 lm 2 device area are also shown in Figures 2(c) and 2(d), presenting all four unipolar switching modes, respectively. It is observed that typical V SET and V RESET are around or below 2 V. It is worth noting that, high switching ratios in the range of 10 6 -10 8 were obtained for all four modes. Asymmetric switching performances between positive bipolar and negative bipolar cycles as well as between positive unipolar and negative unipolar cycles are observed.…”

“…All four possible modes of nonpolar resistive switching were achieved with ON/OFF ratio in the range 10 6 -10 8 . Detailed current-voltage I-V characteristics analysis suggests that the conduction mechanism in low resistance state is due to the formation of metallic filaments.…”

“…10 Furthermore, despite of different device configurations, most reported nonpolar RMs are attributable to the same conductive filaments when subject to positive V SET or negative V SET , hence similar resistant states, i.e., R ON , R OFF , and switching ratios were observed. 5,8 For example, positive bipolar and negative bipolar switching performance can be similar or symmetric. 6 If the change of polarity could also induce asymmetric switching performance such as R ON , R OFF , and switching ratios, this may be further exploited to expand the potential programmable range of future RMs.…”

“…5,6 Relatively speaking, bipolar switching features faster switching speed, better uniformity, and lower operation power, 7 while unipolar switching presents higher ON/OFF ratios (R OFF /R ON ) and presents advantages for high density integration. 8 Thus nonpolar RMs which exhibit both unipolar and bipolar switching behaviours have been considered advantageous as they can potentially expand application scopes of RMs. 9 It is worth noting that there can be two possible bipolar switching modes in one device which can be defined as positive bipolar achieved by positive SET voltage (V SET ) followed by negative RESET voltage (V RESET ) and negative bipolar achieved by negative V SET followed by positive V RESET .…”

“…Most of them are transition metal oxide based RMs 4,5 or insulating material based RMs with metal dopants or particles embedded in the switching layers. 6,8 However, introduction of dopants into the switching layers can reduce the resistance in HRS, leading to limited ON/OFF ratios. 10 Furthermore, despite of different device configurations, most reported nonpolar RMs are attributable to the same conductive filaments when subject to positive V SET or negative V SET , hence similar resistant states, i.e., R ON , R OFF , and switching ratios were observed.…”