Resistive switching behavior of solution-processed AlO_x and GO based RRAM at low temperature

Abstract

This paper reports on resistive switching behavior observed in resistive random access memory (RRAM) devices fabricated with aluminum oxide (AlO_x) and graphene oxide (GO) dielectric films, which were solution-processed under low annealing temperatures of 250 °C and 50 °C for AlO_x and GO dielectric films, respectively. As representative of metal oxide and two-dimensional material, a detailed study and comprehensive comparison in view of resistive switching performance has been conducted for AlO_x and GO based RRAM, including operation voltage, resistance distribution, resistance ratio, conduction mechanism and retention/endurance property. A smaller operation voltage and better stability were demonstrated in AlO_x based RRAM devices while higher resistance magnitude of high resistance state (HRS) and resistance ratio were observed in GO based RRAM devices. The current study opens up promising applications of environmental-friendly solution-processed AlO_x and GO films with lower energy consumption for non-volatile memory (NVM).

Introduction

There are theoretical limitations observed in conventional memories like relatively slow operation speed [1], lack of flexibility [2] and low scalability [3]. As a potential replacement for next-generation non-volatile memories (NVM), resistive random access memory (RRAM) devices based on resistive switching (RS) behavior have received considerable attention in recent years. In order to reduce power consumption, accelerate data processing and increase storage density, a large variety of solid-state materials have been investigated as storage medium for RRAM device applications, including metal oxides such as NiO_x, TiO_x and AlO_x [4], [5], [6], [7], [8], [9], organics [10], [11], [12], complex perovskite oxides [13], [14], [15], [16] and carbon-based materials [17], [18], [19]. In particular, metal oxides and carbon-based materials are currently extensively discussed due to the material simplicity [20], [21], [22].

Among various metal oxide based materials, AlO_x has attracted considerable attention as dielectric layer with advantages of high dielectric constant (~8), superior elasticity, high toughness and high thermal stability with Si and Pt [23], [24], [25], [26], [27], [28], which shows a great potential as RS layer. Apart from the research on metal oxides, carbon-based materials, as an important class of materials anticipated to overcome the technological barriers of conventional semiconductor electronics, have also been explored extensively in recent years [29], [30], [31]. Related research on carbon-based materials applied in the field effect transistor (FET) devices [32], [33] indicate that it is highly important to investigate their memory behavior as well. Among carbon-based materials, graphene oxide (GO) has been actively investigated having advantages such as, easy synthesis process, nanometer-level scaling down and compatibility for flexible device applications [34], [35], [36]. He et al. has been the first to report reliable and reproducible RS performance of GO thin films deposited by vacuum filtration method [37]. Following on from this study, a large amount of publications have reported on high ON/OFF ratio in the GO based RRAM devices [38], [39], revealing the potential of using GO in RRAM devices. Several fabrication methods such as, atomic-layer-deposition (ALD) [22], [40], [41], [42], magnetron sputtering [43], [44], vacuum filtration [45], [46] and solution-processed (SP) methods [47], [48] have been reported to achieve good performance of RRAM devices. Compared to traditional methods, the solution-processing such as drop casting [49], dip coating [50] and spin coating [47] have considerable appeal due to advantages of low fabrication cost, easy operation and high fabrication efficiency [47], [48], [49], [50].

In this work, the solution-processed dielectrics were fabricated at low annealing temperatures of 250 °C for AlO_x film and 50 °C for GO film, and formed the Al/TiN/AlO_x/Pt and Al/GO/Si/Al RRAM devices, respectively. A detailed study of RS performance for Al/TiN/AlO_x/Pt and Al/GO/Si/Al RRAM devices have been conducted, including operation voltage/resistance distribution, retention and endurance properties. A smaller operation voltage and better stability were demonstrated in AlO_x-based RRAM devices while higher resistance of high resistance state (HRS) and higher resistance ratio were observed in GO-based RRAM devices. In addition, the conduction mechanisms of RRAM devices were studied and found to be trap-assisted space-charge-limited conduction (SCLC) in Al/TiN/AlO_x/Pt devices and Frenkel-Poole emission in Al/GO/Si/Al devices.