Electrical properties of Ag/In2O3/M (M = LaNiO3, Pt) devices for RRAM applications

Recent observations of room-temperature resistive switching driven by electric fields in various binary oxides such as NiO, TiO2, CuO, ZrO2 etc. and perovskite oxides such as Cr doped SrTiO3 and manganite Pr0.7Ca0.3MnO3 (PCMO) has triggered a lot of interests due to their potential use for non-volatile resistance random access memory (RRAM) applications. The latter has shown memory retention behavior exceeding 18 months. Resistance switching properties of nanostructure In2O3 films grown on Pt and LaNiO3 (LNO) bottom electrode have been investigated. Ceramic targets of LNO and In2O3 were used for pulsed laser deposition (PLD) using KrF excimer laser (e = 248 nm). LNO film (18 nm) was deposited by PLD on sonicated SiO2 substrates. In2O3 films (160 nm) were deposited on part of the conducting LNO/SiO2 as well as Pt/Ti/SiO2/Si by PLD using a metal shadow mask, to form In2O3/LNO/SiO2 and In2O3/Pt/Ti/SiO2/Si heterostructures, respectively. High purity Ag was thermally evaporated on In2O3 active layer to form top electrode. The Ag/In2O3/M (M = LNO, Pt) structure was characterized by grazing incidence XRD, AFM and cross sectional SEM. Polycrystalline growth of oxides LNO and In2O3 was confirmed by GIXRD, where as AFM show nanostructure growth with smooth surface morphology. Two terminal I-V characteristics carried out by using Kiethley 4200 PlV semiconductor characterization system, showed reproducible hysteresis suggesting two distinct resistance states in the film. Typical resistance switching ratio (Ron/Roff) of the order of 113% and 72% have been estimated for In2O3 device grown on LNO and Pt substrates, respectively. The observed resistance switching characteristics offers lot of promise for new class of binary oxide materials with oxide (LNO) as bottom electrode leading to better suitability for nanoelectronic RRAM devices. The mechanism of the observed resistance switching is analyzed by space charge limited current (SCLS) and the Schottky-like barrier formation at Ag/In2O3 interface in the off states, whereas, Pool-Frankel type conduction mechanism seems valid in the on state. Role of oxygen electro migration at the interface will also be highlighted. (author)