Thermally Driven Resistive Switching in Solution-Processable Thin Films of Coordination Polymers

Abstract

Metal−organic coordination polymers (CPs) downsized to thin films with controllable electrical conductivity are promising for electronic device applications. Here we demonstrate, for the first time, thermally driven resistive switching in thin films of semiconducting CPs consisting of silver ion and tetracyanoquinodimethane ligand (AgTCNQ). High-quality and highly hydrophobic thin films of Ag-TCNQ were fabricated through a layer-by-layer approach upon sacrificing a pre-deposited layer of Cu-TCNQ on a thiolated Au substrate. Reversible switching between the high-resistance state (HRS) at 300 K and the low-resistance state (LRS) at 400 K with an enhancement factor of as high as ∼10 6 in the electrical resistance was realized. The phenomenon is attributed to the alternation of the Schottky barrier at the metal−semiconductor interface by thermal energy and not due to the formation of a conductive filament. Our discovery of thermally driven resistive switching as well as sacrificial growth of CP thin films on an organically modified substrate holds promise for the development of solution-processable non-volatile memory devices.

Perspective on the Interfacial Reduction Reaction

“…Upon dosing I 2 vapor with a Cu-TCNQ thin film device, an unusual rectification in the electrical conductance was observed, which can be attributed to the formation of a Cu-I/Cu-TCNQ heterostructure, an interesting effect of chemical reaction at the solid–gas interface involving CP (Figure c). It is worthwhile to mention that our Cu-TCNQ (also Ag-TCNQ) thin film is prone to exhibit thermally driven resistive switching (10 7 Ω at 300 K ↔ 10 Ω 400 K), which is an interfacial phenomenon unlike earlier reports on chemically driven and/or structurally driven resistive switching in thin films of Cu-TCNQ …”

“…Thus, we observed a spontaneous reduction of Cu­(II) to Cu­(I) at the solid–liquid interface, also known as IRR. Notably, in the liquid- phase (i) no reduction of Cu­(II) to Cu­(I) vis-à-vis the formation of Cu-TCNQ took place upon mixing ethanolic Cu­(OAc) 2 and TCNQ solutions and (ii) Cu­(I)-TCNQ was precipitated out upon mixing CuI and TCNQ solutions almost instantaneously …”

Achieving current rectification ratios ≥ 105 across thin films of coordination polymer

“…S16 †). 32,53 The Raman band of pristine Cu-TCNQ at 520 cm À1 (perhaps due to the Cu/Cu interaction mode) was absent in our doped thin lm (Fig. S17 †).…”

“…Electrical transport measurements (I-V) on various thin lm samples were carried out using a Keithley 4200 SCS Parameter Analyser system attached to an Everbeing probe station (equipped with a thermal chuck) with a eutectic gallium indium (EGaIn) alloy as the top electrode. 53…”

Recent advances on crystalline materials-based flexible memristors for data storage and neuromorphic applications

“…chemical sensors, and energy storage [89][90][91][92]. Moreover, in the process of continuous research, MOFs have been reported as promising candidates for flexible resistive switching and memristor applications [28,46,[93][94][95][96][97][98][99][100].…”