Annealing Effects on Hydrophobic AlN Coatings

Abstract

The effects of annealing at various annealing temperature on hydrophobic AlN coatings were investigated. AlN coatings were deposited in Ar/N2 plasma by using reactive magnetron sputtering process. Two medium frequency (MF) powered Al targets were used. AlN coatings were annealed in air at 300°C, 600°C, 700°C, 800°C, 900°C, 1000°C and 1100°C, respectively. The hydrophobic and hydrophilic properties were evaluated by using water contact angle (WCA) measurement. Microstructure and morphology were observed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray Photoelectron Spectrometer (XPS), respectively. According to the results revealed by XRD and SEM, AlN possess hexagonal close-packed (hcp) structures and good crystallization. The morphology of AlN coating after annealing at 800°C is still similar to the as-deposited AlN coating. As the annealing temperature increases to 1000°C, the XRD peaks of Al2O3 phase can be clearly identified. The main XRD peaks of the AlN coatings still can be found after annealing at 1100°C. The as-deposited AlN coating exhibits hydrophobic behavior and the highest WCA of 119°. As the annealing temperature increases to 300°C, the WCA decreases sharply to 77°. The lower WCA of AlN coatings obtained after annealing is related to the Al2O3 thin films upon AlN coatings.