Advances in Resistive Switching Memories Based on Graphene Oxide

Abstract

Memory devices are a prerequisite for today’s information technology. In general, two different segments can be distinguished. Random access type memories are based on semiconductor technology. These can be divided into static random access memories (SRAM) and dynamic random access memories (DRAM). In the following, only DRAM will be considered, because it is the main RAM technology for standalone memory products. Mass storage devices are traditionally based on magnetic- and optical storage. But also here semiconductor memories are gaining market share. The importance of semiconductor memories is consequently increasing (Mikolajick et al., 2009). Though SRAM and DRAM are very fast, both of them are volatile, which is a huge disadvantage, costing energy and additional periphery circuitry. Si-based Flash memory devices represent the most prominent nonvolatile data memory (NVM) because of their high density and low fabrication costs. However, Flash suffers from low endurance, low write speed, and high voltages required for the write operations. In addition, further scaling, i.e., a continuation in increasing the density of Flash is expected to run into physical limits in the near future. Ferroelectric random access memory (FeRAM) and magnetoresistive random access memory (MRAM) cover niche markets for special applications. One reason among several others is that FeRAM as well as conventional MRAM exhibit technological and inherent problems in the scalability, i.e., in achieving the same density as Flash today. In this circumstance, a renewed nonvolatile memory concept called resistance-switching random access memory (RRAM), which is based on resistance change modulated by electrical stimulus, has recently inspired scientific and commercial interests due to its high operation speed, high scalability, and multibit storage potential (Beck et al., 2000; Lu & Lieber, 2007; Dong et al., 2008). The reading of resistance states is nondestructive, and the memory devices can be operated without transistors in every cell (Lee et al., 2007; Waser & Aono, 2007), thus making a cross-bar structure feasible. A large variety of solid-state materials have been found to show these resistive switching characteristics, including solid electrolytes such as GeSe and Ag2S (Waser & Aono, 2007), perovskites such as SrZrO3 (Beck et al., 2000), Pr0.7Ca0.3MnO3 (Liu et al., 2000; Odagawa et al., 2004; Liao et al., 2009), and BiFeO3 (Yang et al., 2009; Yin et al., 2010), binary transition metal oxides such as NiO (Seo et al., 2004; Kim et al., 2006; Son & Shin, 2008), TiO2 (Kim et al., 2007; Jeong et al., 2009; Kwon et al., 2010), ZrO2 (Wu et al., 2007; Guan et al., 2008; Liu et al., 2009), and ZnO (Chang et al., 2008; Kim et al., 2009; Yang et al., 2009), organic materials (Stewart et al., 2004), amorphous silicon (a-Si) (Jo and Lu, 2008; Jo et al., 2009), and amorphous carbon (a-C) (Sinitskii & Tour, 2009; Zhuge et al., 2010) (Zhuge et al., 2011).