Chlorine-passivation of ozone-treated SnO₂ thin films: Occurrence of oxygen vacancies to manipulate conducting states and bipolarities in resistive switching

Highly conductive SnO₂ thin films are of interest in transparent conducting electrodes for displays and n-type transport layer for perovskite solar cells. We fabricated SnO₂ thin films by spin coating with ozone exposure. This process compensates for the oxygen vacancy states of the films. A local current–voltage measurement by conductive atomic force microscopy revealed the conducting characteristics of the films. Under different ambient conditions, the films exhibited an exotic cycling bipolarity in their resistive switching phenomena, which is likely dependent on the distinct formation of the oxygen vacancies. After application of a chlorine-based surface coating, the SnO₂ surface showed an identical bipolar resistive switching. In particular, the chlorine-passivation was simple and robust to control oxygen vacancies and conducting states, which yields a low power operation below 1–2 V and a huge difference between low- and high-resistant states of a 10⁸–10¹⁰ order of magnitude. Ozone-treated and chlorine-passivated oxide beyond SnO₂ will provide guidance for optoelectronic device improvement.