Synaptic Characteristics from Homogeneous Resistive Switching in Pt/Al2O3/TiN Stack

Abstract

In this work, we propose three types of resistive switching behaviors by controlling operation conditions. We confirmed well-known filamentary switching in Al2O3-based resistive switching memory using the conventional device working operation with a forming process. Here, filamentary switching can be classified into two types depending on the compliance current. On top of that, the homogeneous switching is obtained by using a negative differential resistance effect before the forming or setting process in a negative bias. The variations of the low-resistance and high-resistance states in the homogeneous switching are comparable to the filamentary switching cases. However, the drift characteristics of the low-resistance and high-resistance states in the homogeneous switching are unstable with time. Therefore, the short-term plasticity effects, such as the current decay in repeated pulses and paired pulses facilitation, are demonstrated when using the resistance drift characteristics. Finally, the conductance can be increased and decreased by 50 consecutive potentiation pulses and 50 consecutive depression pulses, respectively. The linear conductance update in homogeneous switching is achieved compared to the filamentary switching, which ensures the high pattern-recognition accuracy.

Practical Approach to Induce Analog Switching Behavior in Memristive Devices: Digital-to-Analog Transformation

“…They observed that applying appropriate stop voltage sweep prior to the LRS, at the negative differential region (NDR) voltage regime, can induce homogeneous switching in the Pt/Al 2 O 3 /TiN devices. Even though the I -V hysteresis of homogeneous switching is less obvious than the filamentary, it was reported that the synaptic behavior of the homogeneous switching is significantly improved, confirming the analog nature of the device [15]. A similar result was also observed in Pt/WO x /W device [16].…”

“…The reversed bias made the switching layer consists of two regions, the oxygenrich region (below the top electrode) and the oxygen-deficient region (above the electrode), which transformed the filamentary into homogeneous switching. The reversed-biased technique can also be useful to transform filamentary bipolar to homogeneous bipolar, as reported by Ryu H. and Kim S. shown in Figure 3(b) [15]. They observed that applying appropriate stop voltage sweep prior to the LRS, at the negative differential region (NDR) voltage regime, can induce homogeneous switching in the Pt/Al 2 O 3 /TiN devices.…”

“…Operating the device at a lower current regime unable to form the filament, but it Several strategies to induce homogeneous switching by controlling the biasing condition. The employment of (a) reversed bias and higher CC in Pt/ZnO/Pt device [14], (b) reversed bias at the NDR region in Pt/Al 2 O 3 /TiN device, [15] (c) successive voltage sweeps prior to the electroformed in the Ag/NiO/Pt device [17], and (d) opposite polarity in Fe-doped SrTiO 3 device [19]. Reprinted and adapted from [14,15,17,19].…”

Bipolar and Complementary Resistive Switching Characteristics and Neuromorphic System Simulation in a Pt/ZnO/TiN Synaptic Device

“…Recently, there have been many efforts to use RRAM as a synapse device for hardware neuromorphic systems [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Multiple conductance can be achieved by using gradual set and reset switching behaviors and low-power operation is one of the strong points of RRAM.…”

Improved Synaptic Device Properties of HfAlOx Dielectric on Highly Doped Silicon Substrate by Partial Reset Process

“…The reset process occurs by Joule heating and it is accompanied by high current. Representatively, unipolar resistive switching has been reported a great deal in NiO, TiO 2 , ZnO, ZrO 2 , and HfO 2 [18][19][20][21][22][23][24][25][26][27]. Although research on URS has been conducted for a long time, the poor distribution of high current, voltage, and resistance values have not been resolved.…”