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.