Narrowing the band gap to enhance the resistive switching properties of Pr3+-doped ZnO thin films by Cd-ion doping

Abstract

Pr³⁺/Cd²⁺ co-doped ZnO hexagonal structure thin films with c-axis preferred orientation were deposited on Pt/Ti/SiO₂/Si substrates using a chemical solution deposition method, and the effect of Cd-ion doping on the resistive switching properties of Zn_0.97−xPr_0.03Cd_xO thin films (x = 0, 0.02, 0.04, and 0.06) has been investigated. The results showed that Cd-doping improved the resistive switching properties of the Pt/Zn_0.97−xPr_0.03Cd_xO/Pt devices. The resistive switching devices exhibited good endurance, long retention, and uniform switching voltages. The resistive switching characteristics also show a good temperature stability beneficial for further device applications. The I–V characteristics and their temperature dependence analysis indicated that the conduction mechanism was ohmic conduction behavior for the low resistance state and at low voltage region for the high resistance state, whereas the conduction mechanism at relatively higher voltage for the high resistance state is trap-controlled space charge limited current. The resistive switching process has been explained using a conductive filament-related formation/rupture mechanism considering the thermal effects and the migration of oxygen vacancies. The reasons for the improvement of resistive switching performance through Cd ion doping, were attributed to the decrease of the band gap and the control of oxygen vacancies.