Effects of Annealing Environments on the Solution‐Grown, Aligned Aluminium‐Doped Zinc Oxide Nanorod‐Array‐Based Ultraviolet Photoconductive Sensor

Abstract

We have fabricated metal‐semiconductor‐metal‐ (MSM‐) type ultraviolet (UV) photoconductive sensors using aluminium‐ (Al‐) doped zinc oxide (ZnO) nanorod arrays that were annealed in different environments: air, oxygen, or a vacuum. The Al‐doped ZnO nanorods had an average diameter of 60 nm with a thickness of approximately 600 nm that included the seed layer (with thickness ~ 200 nm). Our results show that the vacuum‐annealed nanorod‐array‐based UV photoconductive sensor has the highest photocurrent value of 2.43 × 10 −4 A. The high photocurrent is due to the high concentration of zinc (Zn) interstitials in the vacuum‐annealed nanorod arrays. In contrast, the oxygen‐annealing process applied to the Al‐doped ZnO nanorod arrays produced highly sensitive UV photoconductive sensors, in which the sensitivity reached 55.6, due to the surface properties of the oxygen‐annealed nanorods, which have a higher affinity for oxygen adsorption than the other samples and were thereby capable of reducing the sensor’s dark current. In addition, the sensor fabricated using the oxygen‐annealed nanorod arrays had the lowest rise and decay time constants. Our result shows that the annealing environment greatly affects the surface condition and properties of the Al‐doped ZnO nanorod arrays, which influences the performance of the UV photoconductive sensors.