Resistive switching behavior and mechanism of HfO x films with large on/off ratio by structure design

Abstract

Different bilayer structures of HfO x /Ti(TiO x ) are designed for hafnium-based memory to investigate the switching characteristics. The chemical states in the films and near the interface are characterized by x-ray photoelectron spectroscopy, and the oxygen vacancies are analyzed. Highly improved on/off ratio (∼104) and much uniform switching parameters are observed for bilayer structures compared to single layer HfO x sample, which can be attributed to the modulation of oxygen vacancies at the interface and better control of the growth of filaments. Furthermore, the reliability of the prepared samples is investigated. The carrier conduction behaviors of HfO x -based samples can be attributed to the trapping and de-trapping process of oxygen vacancies and a filamentary model is proposed. In addition, the rupture of filaments during the reset process for the bilayer structures occur at the weak points near the interface by the recovery of oxygen vacancies accompanied by the variation of barrier height. The re-formation of fixed filaments due to the residual filaments as lightning rods results in the better switching performance of the bilayer structure.