A novel fabrication process for nanostructured Al-doped ZnO thin film based humidity sensors

The properties of Aluminum (Al) doped Zinc Oxide (ZnO) nanostructures thin film prepared by a novel immersed method for humidity sensors are presented. The electrical properties of the thin film were characterized using Current-Voltage (I-V) measurement (Keithey 2400). The structural properties were characterized using Photoluminescence (PL) and Scanning Emission Microscope. I-V were measured at different relative humidity (RH) from for 30%-90% for every immerse time samples. The thin film were deposited on the glass substrate using spin coating technique and immerse while the Aluminum doped ZnO were prepared using Sol-gel method. The sol-gel method produced the Aluminum doped ZnO that have the single nanorods particles mixed with some cluster of rods. The effects of Al doping concentration at 0 at %, 2 at %, 6 at % on the Al doped ZnO thin film properties were investigated. PL show an emissions band with two peaks centered at about 380 nm (ultra-violet (UV)) and 600 nm (green) in a room temperature. The variation in visible emission intensity at 600 nm was attributed to the probability of formation of defects dominated by dopant concentration. The SEM investigations show that length of the nanorods size increase as the doping concentration increase. Zinc oxides doped with Aluminum at 6 at % are found to be a good sensitivity material for humidity sensor since the sensitivity of the thin film is higher than other samples.