Memristive Non-Volatile Memory Based on Graphene Materials

Abstract

Resistive random access memory (RRAM), which is considered as one of the most promising next-generation non-volatile memory (NVM) devices and a representative of memristor technologies, demonstrated great potential in acting as an artificial synapse in the industry of neuromorphic systems and artificial intelligence (AI), due its advantages such as fast operation speed, low power consumption, and high device density. Graphene and related materials (GRMs), especially graphene oxide (GO), acting as active materials for RRAM devices, are considered as a promising alternative to other materials including metal oxides and perovskite materials. Herein, an overview of GRM-based RRAM devices is provided, with discussion about the properties of GRMs, main operation mechanisms for resistive switching (RS) behavior, figure of merit (FoM) summary, and prospect extension of GRM-based RRAM devices. With excellent physical and chemical advantages like intrinsic Young’s modulus (1.0 TPa), good tensile strength (130 GPa), excellent carrier mobility (2.0 × 105 cm2∙V−1∙s−1), and high thermal (5000 Wm−1∙K−1) and superior electrical conductivity (1.0 × 106 S∙m−1), GRMs can act as electrodes and resistive switching media in RRAM devices. In addition, the GRM-based interface between electrode and dielectric can have an effect on atomic diffusion limitation in dielectric and surface effect suppression. Immense amounts of concrete research indicate that GRMs might play a significant role in promoting the large-scale commercialization possibility of RRAM devices.

Advances of RRAM Devices: Resistive Switching Mechanisms, Materials and Bionic Synaptic Application

“…This 9-nmthickness device exhibited excellent repeatable RS cycles with number of endurance pulses over 10 5 and retention time longer than 3 × 10 4 s. In addition, some RRAM devices with noble metal as both TE and BE also demonstrated bipolar switching performance, such as Pt/sputtering-deposited Cr2O3/Pt reported by Chen et al [132], Pt/sputtering-deposited TaOx/Pt reported by Huang et al [133], Pt/Ni/ECD (electrochemical deposition)-fabricated CuOx/Ni/Pt, and Pt/sputtering-deposited SiO2/Pt reported by Park et al [134]. Apart from elementary substance metals mentioned, carbon-based materials such as graphene and carbon nanotubes [48,62,131,135], conductive oxides such as ITO (indium tin oxide) [131], and complex nitrides such as TiN and TaN [20,85] are also charming as selection of RRAM electrodes. ITO electrode has been widely utilized in electronic devices as well as RRAM cells due to its excellent electrical conductivity, high light transmittance and high hardness [48].…”

“…Before we present an investigation of materials application, it is necessary to provide brief induction of figures of merit (FoMs), which are mainly used to assess the performance of RRAM devices, including operation speed, power consumption, reliability, scalability, and cost [62]. Operation speed is defined by random-access time and effective time of write & erase (w & e) speed of a single RRAM cell; power consumption is affected by static and dynamic power consumption; reliability consists of endurance; retention properties are used to determine whether an RRAM device is reliable; scalability of an RRAM device determines whether RRAM devices can be developed in line with current trends of increasing device density; and the cost directly has an impact on marketization or mass-production of the proposed devices [62]. Apart from the main FoMs presented above, some other specific characteristics of FoMs such as SET/RESET voltage, ON/OFF switching ratio, distribution of operation voltage, and resistance cannot be neglected accordingly.…”

“…The excellent electrical conductivity of graphene and ITO made the devices operate under low CC (<100 μA) with low voltage (<1 V) and low power consumption (<100 μW). The device also demonstrated a resistance ratio between HRS and LRS higher than 10 4 during 200 successful switching cycles and retention longer than 10 4 s. Apart from elementary substance metals mentioned, carbon-based materials such as graphene and carbon nanotubes [48,62,131,135], conductive oxides such as ITO (indium tin oxide) [131], and complex nitrides such as TiN and TaN [20,85] are also charming as selection of RRAM electrodes. ITO electrode has been widely utilized in electronic devices as well as RRAM cells due to its excellent electrical conductivity, high light transmittance and high hardness [48].…”

“…Apart from elementary substance metals mentioned, carbon-based materials such as graphene and carbon nanotubes [ 48 , 62 , 131 , 135 ], conductive oxides such as ITO (indium tin oxide) [ 131 ], and complex nitrides such as TiN and TaN [ 20 , 85 ] are also charming as selection of RRAM electrodes. ITO electrode has been widely utilized in electronic devices as well as RRAM cells due to its excellent electrical conductivity, high light transmittance and high hardness [ 48 ].…”

Long-Term Memory Performance with Learning Behavior of Artificial Synaptic Memristor Based on Stacked Solution-Processed Switching Layers

“…Among these electronic devices, resistive random access memory (RRAM) of non-volatile memory (NVM) has attracted a tremendous amount of attention due to its nanoJoule-level power consumption, picosecond-level read & write speed and ~year-level service life [1,4]. For now, it has been proved that oxide materials, including metal oxide (MO) (AlOx, HfOx and NiO) and nonmetal oxides (graphene oxide (GO) and phosphorus oxide (POx)), could demonstrate stable resistive switching (RS) performance in RRAM devices [3,[5][6][7]. However, most oxide RS layers were deposited by traditional fabrication methods like atomic layer deposition (ALD), sputtering and chemical vapor deposition (CVD).…”