Nanostructures on Sapphire Surfaces Induced by Metal Impurity Assisted Ion Beam

• Main Authors: Qian Bi, Zhili Chen, Yuzhao Liu, Li Tang, Yingxue Xi, Weiguo Liu
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Coatings
• Subjects: self-organized nanostructure; surface morphology; root-mean-square roughness (RMS); sapphire; ion beam; atomic force microscope (AFM)
• Online Access: https://www.mdpi.com/2079-6412/10/10/949

The metal impurity assisted ion beam technology has shown its uniqueness and effectiveness in the formation and precise control of nanostructures on the surface of materials. Hence, the investigation in this area is vital. The morphology evolution of self-organized nanostructures induced by Fe co-deposition assisted Ar⁺ ion beam sputtering at a different distance from the impurity target was investigated on sapphire, using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). We also investigated the role of metal impurities on sapphire ripple formation. Experiments were carried out at an oblique angle of incidence 65°with constant ion beam current density 487 μA/cm² and the erosion duration of 60 min at room temperature (20 °C). The introduction of Fe impurity increased the longitudinal height and roughness of the surface nanostructures. Moreover, the amounts of Fe deposited on the surface decreased with increasing distance, and the morphology of the smooth sapphire surface demonstrated a strong distance dependence. Differences in surface morphology were attributed to changes in metal impurity concentration. With an increase of impurity target distance, island-like structures gradually evolved into continuous ripples. At the same time, the orderliness of nanostructures was enhanced, the longitudinal height gradually decreased, while the spatial frequency was unchanged. In addition, there were very few metal impurities on the etched sample. During the ion beam sputtering process, island-like structures promoted the growth of ripples but destroyed their orderliness.