Noble-Metal-Free Memristive Devices Based on IGZO for Neuromorphic Applications

Amorphous indium-gallium-zinc-oxide (a-IGZO) based memristive devices with molybdenum contacts as both top and bottom electrodes are presented aiming to be used in neuromorphic applications. Devices down to 4 mu m(2)are fabricated using conventional photolithography processes, with an extraordinary yield of 100%. X-ray photoelectron spectroscopy and transmission electron microscopy performed on the developed structures confirm the presence of a thin intermixed oxide layer (4-5 nm) containing Mo(6+)oxidation state at the interface with the bottom contact. This results in Schottky diode-like characteristics at the pristine state with a rectification ratio of 3 orders of magnitude. The devices have electroforming-free and area-dependent analog resistive switching properties. Temperature analysis of resistive switchingI-Vdata reveals barrier height variations of the junction. Several synaptic functions, such as synaptic potentiation and depression as response to programmed pulses, short- to long-term plasticity transition (STP to LTP) and "learning experience" properties are presented. The Mo/IGZO/Mo memristive device shows potential application of an electronic synapse for brain-inspired computing application. Integration in System-on-Panel architectures is possible at negligible cost, because all materials are used in commercial IGZO thin-film transistor fabrication.