Nanotribological Behavior of Ultra-thin Al2O3 Films Prepared by Atomic Layer Deposition

Si-based nano/micro-electromechanical system (NEMS/MEMS) devices with contacting and rubbing structures cannot run reliably due to their poor tribological performance. A thin alumina (Al₂O₃) film is a promising candidate for the protective coating in the applications of NEMS/MEMS devices. In this study, nanotribological behavior of ultra-thin Al₂O₃ films prepared by atomic layer deposition on a Si (100) substrate was investigated in comparison with that of Si (100). X-ray photoelectron spectroscopy was used to determine the composition of Al₂O₃ films. Atomic force microscopy with different tips was employed to measure the scratch resistance, adhesion and friction forces of various samples. The results show that Al₂O₃ films have larger scratch resistance than that of Si (100). In addition, the adhesion and friction forces of Al₂O₃ films are smaller than that of Si (100). Thus, the Al₂O₃ films are capable of a wide application in Si-based NEMS/MEMS devices. The improved tribological performance of Al₂O₃ films is attributed to their hydrophobic properties.