%0 Journal Article
%T Bipolar Switching Characteristics of RRAM Cells with CaBi4Ti4O15 Film
%A Jian-Yang Lin
%A Chia-Lin Wu
%J Advances in Materials Science and Engineering
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/425085
%X The electrical conduction and bipolar switching properties of resistive random access memory (RRAM) cells with transparent calcium bismuth titanate (CaBi4Ti4O15¡ªCBTi144) thin films were investigated. Experimentally, the (119)-oriented CBTi144 thin films were deposited onto the ITO/glass substrates by RF magnetron sputtering followed by rapid thermal annealing (RTA) at a temperature range of 450¨C550¡ãC. The surface morphologies and crystal structures of the CBTi144 thin films were examined by using field-emission scanning electron microscopy and X-ray diffraction measurements. The on/off ratio and switching behaviors of the transparent Al/CBTi144/ITO/glass RRAM devices were further discussed in this work. 1. Introduction Recently, various new nonvolatile memory devices were investigated, such as ferroelectric random access memory (FeRAM), resistive random access memory (RRAM), and phase change memory (PCM). Especially, the RRAM that composed of a simple metal-insulator-metal (MIM) structure has the advantages of low power consumption, high speed operation, good retention, and high-density integration capability [1¨C3]. Recent RRAM research includes perovskite oxides and metal oxides with different electrodes such as VO [4], Pr0.7Ca0.3MnO3 [5], NiO [6], La2O3 [7], Dy2O3 [8], and ZnO [9]. Several perovskite materials, such as SrBi4Ti4O15 (SBT) [10], (Ba0.7Sr0.3)(Ti0.9Zr0.1)O3 [11], CaBi4Ti4O15 (CBT) [12, 13], CaBi4£¿xNdxTi4O15 (CBNT) [14], and Ca1£¿xLaxBi4(Ti0.9W0.1)4O15 (CLBTW) [15], have been developed and investigated recently. Especially, the CBT film has high Curie temperature and low current density [16, 17]. In this study, we have investigated the bipolar resistive switching properties of the CBTi144 thin films in the metal-insulator-metal (MIM) structure for memory application. 2. Experiment In this study, the CBTi144 thin films were deposited onto the ITO/glass substrates by RF magnetron sputtering with a ceramic CBTi144 target. Ceramic target of CBTi144 was prepared by conventional solid-state reaction technique. First, raw materials of Bi2O3, CaO, and TiO2 were weighted first according to the stoichiometric ratio of CaBi4Ti4O15. After mixing of the raw materials, the mixed material was ball-milled for 5£¿h. The mixture was then dried and calcined at 1100¡ãC for 4£¿h. Finally, the CBTi144 target was formed with a diameter of 2 inches. The CBTi144 films of 300£¿nm thickness were then deposited onto the ITO/glass substrates by RF magnetron sputtering with the CBTi144 target. The preparation conditions of the CBTi144 thin films are summarized in Table 1. To
%U http://www.hindawi.com/journals/amse/2014/425085/