Laser-Fabricated Reduced Graphene Oxide Memristors

Abstract

Finding an inexpensive and scalable method for the mass production of memristors will be one of the key aspects for their implementation in end-user computing applications. Herein, we report pioneering research on the fabrication of laser-lithographed graphene oxide memristors. The devices have been surface-fabricated through a graphene oxide coating on a polyethylene terephthalate substrate followed by a localized laser-assisted photo-thermal partial reduction. When the laser fluence is appropriately tuned during the fabrication process, the devices present a characteristic pinched closed-loop in the current-voltage relation revealing the unique fingerprint of the memristive hysteresis. Combined structural and electrical experiments have been conducted to characterize the raw material and the devices that aim to establish a path for optimization. Electrical measurements have demonstrated a clear distinction between the resistive states, as well as stable memory performance, indicating the potential of laser-fabricated graphene oxide memristors in resistive switching applications.

Keywords: flexible electronics; graphene oxide; laser-scribing; memristor; neuromorphic.

Figure 1

(a) Schematic of the CNC-driven laser used for the fabrication of rGO memristors. The spatial resolution of the system used in this work is 10 µm. (b) Actual picture of one of the laser-fabricated memristors (L = 2.2 mm, W = 1 mm) using microdrops of bare conductive electric paint^TM as contacting electrodes. (c) Sheet resistance of laser-reduced graphene oxide samples (4 mg/mL) on PET treated at different laser powers (λ = 405 nm) extracted by the transmission line method (TLM) [27]. Error bars were calculated as the standard deviation of 15 different samples for each laser power.

Figure 2

Structural characterization. (a) SEM image of laser-reduced graphene oxide at 70 mW (initial GO colloid concentration 0.5 mL/cm²). (b) Raman spectra acquired from the GO film before and after the laser-assisted reduction for different laser powers. (c) Comparison of the C1s peak from the XPS spectrum of both GO (top) and laser-reduced GO (bottom) samples. (d) ATR-FTIR spectra of unreduced GO. (e) ATR-FTIR spectra of 100 mW laser-reduced GO.

Figure 3

Electrical performance of a laser-reduced GO memristor (P_laser = 70 mW, L = 2.2 mm, W = 1 mm). (a) Current-voltage characteristic of a memristor showing the characteristic signature of memristance. The voltage has been scanned from −3 V to 3 V with a voltage step of 10 mV. The scanning rate was adjusted to 2 V/s. The top inset of the figure shows an example of another device fabricated with Ag-based contacts. (b) Ratio of the resistance measured in the high resistance state (HRS) and low resistance state (LRS) of a set of laser-lithographed graphene oxide memristors fabricated at different laser power (15 devices for each laser power). The resistance was extracted in the range [−1,1] V of the current-voltage characteristics. The memristors were of identical dimensions with an effective length of 2.2 mm and width of 1 mm.

Figure 4

(a) Resistance values obtained from successive programming/erasing cycles without current compliance. Average values of the resistance at the HRS and LRS are included. (b) Resistance values obtained from successive device cycling demonstrating up to 100 cycles. The experiments were carried out by establishing a current compliance of 20 µA. (c) Resistance values obtained from 15 different memristors at the HRS and LRS states. Error bars illustrate the resistance variability of the device during 10 cycles. (d) Retention characteristic of laser-reduced graphene oxide memristor at room temperature (same device for LRS and HRS states). The state of the device is read with 0.2 V pulses during 50 ms.

Figure 5

Conceptual model of the origin of the resistive switching of laser-fabricated graphene oxide memristors illustrating the transition from HRS to LRS. Starting from an HRS state, under the action the current flow, the electrostatic potential is mostly applied on the non-conductive sp³ domains resulting in large local electric fields. The sp² based conductive domain (area surrounded by the green dashed line) is extended by the field-assisted migration of oxygen ions, creating a local high conductivity path leading to an LRS state.