Abstract
Resistance switching (RS) devices with ultra-thin Ta2O5 switching layer (0.5–2.0 nm) with a cell diameter of 28 nm were fabricated. The performance of the devices was tested by voltage-driven current—voltage (I-V) sweep and closed-loop pulse switching (CLPS) tests. A Ta layer was placed beneath the Ta2O5 switching layer to act as an oxygen vacancy reservoir. The device with the smallest Ta2O5 thickness (0.5 nm) showed normal switching properties with gradual change in resistance in I-V sweep or CLPS and high reliability. By contrast, other devices with higher Ta2O5 thickness (1.0–2.0 nm) showed abrupt switching with several abnormal behaviours, degraded resistance distribution, especially in high resistance state, and much lower reliability performance. A single conical or hour-glass shaped double conical conducting filament shape was conceived to explain these behavioural differences that depended on the Ta2O5 switching layer thickness. Loss of oxygen via lateral diffusion to the encapsulating Si3N4/SiO2 layer was suggested as the main degradation mechanism for reliability, and a method to improve reliability was also proposed.
Highlights
Many of the previous works have adopted
An appropriate switching mechanism based on the hour-glass shaped conducting filaments (CF) model, regarding the generation and configuration of CF in the ultra-thin Ta2O5 layer depending on the thickness, was suggested to explain such critical differences
A schematic diagram and transmission electron microscopy (TEM) image of the TiN/Ta2O5/Ta/TaN device are shown in Fig. 1a,b, respectively
Summary
Abrupt electroforming and abnormal RESET behaviour of thicker Ta2O5 devices. A schematic diagram and transmission electron microscopy (TEM) image of the TiN/Ta2O5/Ta/TaN device are shown in Fig. 1a,b, respectively. While the device with the smallest Ta2O5 thickness showed normal switching properties with a gradual change in resistance and high reliability in voltage sweep or pulse switching, other devices with larger Ta2O5 thickness showed several abnormal behaviours with respect to the detailed SET and RESET processes, degraded resistance distribution, especially in HRS, and much lower reliability performance These critical differences could be explained by the one sided CF model for the former case, where the gradual expansion and contraction of it are responsible for the reliable RS, and double sided hour-glass shaped CF model for the latter case, which involved much complicated evolution of CF shape and many abnormal behaviours. Encapsulating the device with thicker oxygen impermeable layer was expected to improve the reliability
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
