Room temperature deposition of stable p-type ZnO:N thin films through chemical species modulation using reactive pulsed laser deposition

Low temperature processing as well as long-term electrical stability are required to match p-type ZnO thin films with flexible electronics applications. Herein, ZnO and ZnO:N thin films were deposited at room temperature by reactive pulsed laser deposition of a zinc metallic target. Several ZnO thin films were obtained by varying the oxygen working pressure from 1.2 x 10(-5) Torr to 3.5 x 10(-2) Torr. Chemical concentration was smoothly tuned as demonstrated by in situ X-ray Photoelectron Spectroscopy. Introducing and varying both N-2 and O-2 fluxes at a constant pressure, N-doped ZnO films from 0.3 at.% to 5 at.% were deposited. Adjusting the N-2/O-2 flux ratio, ptype ZnO:N films were successfully achieved, exhibiting a carrier concentration of 5.3 x 10(18) cm(-3), resistivity of 2 Omega cm, and mobility of 0.5 cm(2)V(-1)s(- 1). Four representative p-type samples were analyzed to confirm chemical and electrical reproducibility. Electrical properties of one of these films were measured again nine months after deposited, and p-type conductivity was still observed. Cathodoluminescence revealed green-dominant emissions in n-ZnO and UV-dominant emissions in p-ZnO:N films as nitrogen doping effect. Finally, a p-n diode was fabricated using photolithography, exhibiting rectification performance even nine months after deposited. P-type ZnO:N presented here are suitable for flexible electronics devices fabrication.