Published online by Cambridge University Press: 21 May 2012
A novel resistive device with a floating electrode (RFED) has been manufactured as a stack of layers Cu/TaOx/Pt/TaOx/Cu in a crossbar array comprising two single resistive switches merged antiserially at the common inert Pt floating electrode. The device exhibits four states HRS/HRS, HRS/LRS, LRS/HRS and LRS/LRS, where HRS and LRS are the high and low resistance states, respectively, with only LRS/LRS being fully conductive. When the voltage on one Cu electrode is increased to a value Vth-on(A), a conductive nanofilament (CF) in switch A is formed, while suppressing CF formation in switch B. When the voltage is then extended to negative bias, a sudden jump in the I-V characteristics is observed at Vth-on(B), when the 2nd CF in switch B is formed rendering the RFED device fully conductive. If the current surge just after the formation of CF in 2nd switch exceeds the reset current of the 1st CF, the 1st CF ruptures shortly thereafter, i.e. the conductive state is destroyed as soon as it has been created. This property proves valuable for applications in neural networks where a generation of a current pulse at a critical threshold is required. The height and the time width of the firing pulse is an inherent property of the device and can be controlled by the parameters of the individual switches and their set/reset operations.