Non-exponential resistive switching in Ag₂S memristors: a key to nanometer-scale non-volatile memory devices

Abstract

The dynamics of resistive switchings in nanometer-scale metallic junctions formed between an inert metallic tip and an Ag film covered by a thin Ag2S layer are investigated. Our thorough experimental analysis and numerical simulations revealed that the resistance change upon a switching bias voltage pulse exhibits a strongly non-exponential behaviour yielding markedly different response times at different bias levels. Our results demonstrate the merits of Ag2S nanojunctions as nanometer-scale non-volatile memory cells with stable switching ratios, high endurance as well as fast response to write/erase, and an outstanding stability against read operations at technologically optimal bias and current levels.

Nanosecond resistive switching in Ag/AgI/PtIr nanojunctions

“…stable nanojunction while f drive was varied over five orders of magnitude. We found that R OFF /R ON linearly increases with while a logarithmic decrease is observed with increasing f drive , in agreement with the so-called "voltage-time dilemma" [22,35] enabling non-volatile data storage. Exemplary traces selected from the parameter regimes highlighted in white in Figure 2a demonstrate these tendencies, as illustrated in Figure 2b and Figure 2c, where either or f drive was stepped while the other parameter was kept constant.…”

“…They were directly followed by the onset of stable hysteretic traces without the need of any further dedicated electroforming procedure. We argue, that the indention of the tip to the surface layer reduces the effective thickness of the dielectric layer resulting in the down-scaling of the electroforming voltage to the range of the set voltage in agreement with the tendency commonly observed in nanoscale resistive switching systems [8,9,22]. Resistive switching was characterized by the analysis of hysteretic I(V) traces that were acquired by using the setup shown in the upper inset of Figure 1a.…”

“…Ag-based filamentary resistive switches [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] have been promoted in terms of the "atomic switch" by K. Terabe et al utilizing Ag 2 S as the ionic conductor medium [28]. The roles of the matrix, the electrode, and their interfaces in the filament formation have been extensively investigated covering a broad range of materials systems [4].…”

“…In this paper we explore the dynamical properties of room-temperature resistive switching established in metallic Ag/AgI/PtIr nanojunctions. Hysteretic I(V) traces were studied as a function of the frequency and the amplitude of triangular voltage signals covering five orders of magnitude in the time domain testifying to the voltage-time dilemma [22,35] commonly observed in Ag-based filamentary resistive switches. In order to challenge device operation in AgI-based nanoswitches down to sub-nanosecond timescales for the first time, a special purpose pulsed microwave setup was developed and successfully utilized to fire 500 ps long set/reset voltage pulses and acquire the resulting resistive switching at 1 GHz bandwidth.…”

Direct TEM observation of the “acanthite α-Ag2S–argentite β-Ag2S” phase transition in a silver sulfide nanoparticle

“…20 Application of nanostructured silver sulde holds much promise in microelectronics, where Ag 2 S/Ag heteronanostructures and nanocomposites are used in nonvolatile memory devices and resistive switches. [21][22][23] Their action is based on the phase transition of acanthite a-Ag 2 S into argentite b-Ag 2 S. [12][13][14][23][24][25][26][27][28] According to the phase diagram of the Ag-S system, 29 silver sulde Ag 2 S has three polymorphic modications. The lowtemperature semiconductor phase a-Ag 2 S (acanthite) with a monoclinic crystal structure exists at temperatures below $450 K. b-Ag 2 S (argentite) phase has a body-centered cubic (bcc) lattice, exists in the temperature range 452-859 K, and possesses superionic conductivity.…”