Probing resistive switching in HfO2/Al2O3 bilayer oxides using in-situ transmission electron microscopy

In this work, we investigate the resistive switching in hafnium dioxide (HfO2) and aluminum oxide (Al2O3) bilayered stacks using in-situ transmission electron microscopy and X-ray energy dispersive spectroscopy. Conductance of the HfO2/Al2O3 stack changes gradually upon electrical stressing which is related to the for-mation of extended nanoscale physical defects at the HfO2/Al2O3 interface and the migration and re -crystallization of Al into the oxide bulk. The results suggest two competing physical mechanisms including the redistribution of oxygen ions and the migration of Al species from the Al electrode during the switching process. While the HfO2/Al2O3 bilayered stack appears to be a good candidate for RRAM technology, the low diffusion barrier of the active Al electrode causes severe Al migration in the bi-layered oxides leading to the device to fail in resetting, and thereby, largely limiting the overall switching performance and material reliability.

Automated summary

In this study, the resistive switching in hafnium dioxide (HfO2) and aluminum oxide (Al2O3) bilayered stacks was investigated using in-situ transmission electron microscopy and X-ray energy dispersive spectroscopy. The change in conductance of the HfO2/Al2O3 stack during electrical stressing is attributed to the formation of extended nanoscale defects at the HfO2/Al2O3 interface and the migration and re-crystallization of Al into the oxide bulk. Two competing physical mechanisms, oxygen ion redistribution and Al species migration, were found to be involved in the switching process. The low diffusion barrier of the active Al electrode causes severe Al migration in the bilayered oxides, leading to device failure in resetting and limiting overall switching performance and material reliability.