Resistive switching characteristics and mechanism of bilayer HfO2/ZrO2 structure deposited by radio-frequency sputtering for nonvolatile memory

• Published in: Results in physics 2020-09, Vol.18, p.103275, Article 103275
• Main Authors: Ismail, Muhammad, Batool, Zahida, Mahmood, Khalid, Manzoor Rana, Anwar, Yang, Byung-Do, Kim, Sungjun
• Format: Article
• Language: English
• Subjects: Bilayer HfO2/ZrO2 structure; Gibbs free energy; Resistive switching; Schottky emission; Thermal conductivity
• ISSN: 2211-3797; 2211-3797
• DOI: 10.1016/j.rinp.2020.103275

•Bilayer HfO2/ZrO2 thin film was deposited by sputtering at RT to investigate RS characteristics.•RS uniformity and mechanism were evaluated by distributions of oxygen vacancies (VOs) in the HfO2 and ZrO2 layers through XPS.•Difference in thermal conductivity and Gibbs free energy of ZrO2 layer and HfO2 layer are responsible for RS characteristics.•Current transport conduction mechanism is Schottky emission in the high field region of HRS.•The VOs-based filamentary model has been proposed to explain physical mechanism. In this study, a bilayer HfO2/ZrO2 thin film structure was deposited by radio frequency sputtering at room temperature (RT) to investigate the resistive switching (RS) characteristics, mechanism as well as their reproducibility. Bilayer HfO2/ZrO2 structured device > 103 DC switching cycles at RT, and > 10 ON/OFF ratio. The RS uniformity and mechanism were evaluated by Gaussian data fitting and distributions of oxygen vacancies (VOs) in the HfO2 and ZrO2 layers through X-ray photo electron spectroscopy (XPS) analysis, respectively. Because of higher thermal conductivity (2.7Wm-1K-1) and lower Gibbs free energy (ΔGo=-1100kJ/mol) of ZrO2 layer as compared to those of HfO2 layer (1.1Wm-1K-1,ΔGo=-1010.8kJ/mol), an easier reduction and oxidation of filaments took place by exchanging oxygen ions with each other (ZrO2/HfO2). A VOs-based filamentary model has been proposed to explain RS mechanism. Furthermore, a current transport mechanism is noted be based on Schottky emission in the high field region of the high resistance states (HRS).