Enhancing Short-Term Plasticity by Inserting a Thin TiO2 Layer in WOx-Based Resistive Switching Memory

Abstract

In this work, we emulate biological synaptic properties such as long-term plasticity (LTP) and short-term plasticity (STP) in an artificial synaptic device with a TiN/TiO2/WOx/Pt structure. The graded WOx layer with oxygen vacancies is confirmed via X-ray photoelectron spectroscopy (XPS) analysis. The control TiN/WOx/Pt device shows filamentary switching with abrupt set and gradual reset processes in DC sweep mode. The TiN/WOx/Pt device is vulnerable to set stuck because of negative set behavior, as verified by both DC sweep and pulse modes. The TiN/WOx/Pt device has good retention and can mimic long-term memory (LTM), including potentiation and depression, given repeated pulses. On the other hand, TiN/TiO2/WOx/Pt devices show non-filamentary type switching that is suitable for fine conductance modulation. Potentiation and depression are demonstrated in the TiN/TiO2 (2 nm)/WOx/Pt device with moderate conductance decay by application of identical repeated pulses. Short-term memory (STM) is demonstrated by varying the interval time of pulse inputs for the TiN/TiO2 (6 nm)/WOx/Pt device with a quick decay in conductance.

Standards for the Characterization of Endurance in Resistive Switching Devices

“…(f) How the values of RHRS and R LRS change with the magnitude of the stress applied, which changes the value of R HRS / R LRS and the variability. Reprinted with permission from ref . Copyright 2020 MDPI.…”

“…g ., larger voltage, current, duration) . The values of R HRS , R LRS , and R HRS / R LRS and their dispersions also depend on the stresses applied (see Figure f) . Moreover, sometimes the resistance of a RS device can get unpredictably stuck at one state for some time ( i .…”

“…50 The values of R HRS , R LRS , and R HRS /R LRS and their dispersions also depend on the stresses applied (see Figure 2f). 51 Moreover, sometimes the resistance of a RS device can get unpredictably stuck at one state for some time (i.e., it stops switching even if read, write, and erase pulses are applied) and recover the normal functioning suddenly. 52 For example, if in one set event too many ions in the MIM cell have been displaced, the voltage applied to induce the reset might not be high enough.…”

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

“…Resistive switching random access memory (RRAM) can act as a synapse in a neuromorphic chip because of its low-power operation [7], fast switching time [8], high-density integration [9], and multi-level cells (MLC) with analogue switching [10][11][12][13][14]. The various resistive switching characteristics are achieved using a dielectric material and metal electrodes [15][16][17][18][19][20][21][22][23][24][25][26][27]. Additionally, the switching type can be changed depending on the operation conditions, such as the current and voltage levels [28].…”

Effects of Oxygen Precursor on Resistive Switching Properties of CMOS Compatible HfO2-Based RRAM

“…Magnetoresistive randomaccess memory (MRAM) also shows resistance change by controlling the magnetization of magnetic material [6]. RRAM has the advantage of being capable of tunable resistive switching, which is applicable to the various application as storage memory [7][8][9][10][11][12][13][14][15][16][17][18][19][20], logicin-memory [21], and neuromorphic computing [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. Moreover, RRAM shows lowpower operation, high endurance, good retention, high-density integration, and good complementary metal-oxide-semiconductor (CMOS) compatibility in terms of process and material.…”