Preparation and characterization of arachidic acid self-assembled monolayers on glass substrate coated with sol–gel Al2O3 thin film

Ultra-thin film of Al2O3 was prepared on glass substrates via a sol–gel method, followed by sintering at 500 °C. The self-assembled arachidic acid monolayers (AHDA-SAM) were then prepared on the glass substrate coated with sol–gel Al2O3 thin film by means of a molecular self-assembly process. The wetting behavior, structure, and morphology of the AHDA-SAM were characterized by means of contact angle measurement, X-ray photoelectron spectroscopic analysis, Fourier transformation infrared spectroscopy, and atomic force microscopy. The friction behavior of the AHDA-SAM on the glass substrate coated with Al2O3 thin film sliding against a Si3N4 ball was examined on a unidirectional friction and wear tester. The worn surfaces of the AHDA-SAM were observed with a scanning electron microscope. Distilled water had a contact angle of approximately 105° on the AHDA-SAM. AHDA-SAM showed excellent antiwear and friction-reducing behavior under a low load (0.5 N) and a low sliding speed (90 mm min−1). The AHDA-SAM was dominated by abrasive wear and plastic deformation in dry sliding against the Si3N4 ball. The glass substrate was endowed with good friction-reducing and antiwear behavior after duplex surface-modification with sol–gel Al2O3 and top layer of AHDA-SAM. This treatment might be of relevance to the surface-modification of single crystal Si and SiC in microelectromechanical systems applications.