Modification of the Adhesive Properties of XeF₂-Etched Aluminum Surfaces by Deposition of Organic Self-Assembled Monolayers

Abstract

Removal of Si sacrificial layer from Al surfaces using XeF2 gas results in highly adhesive aluminum (oxy)fluoride surfaces. We describe the preparation and characterization of improved, highly nonstick surfaces modified with octadecyltrichlorosilane (OTS). High hydrophilicity of the AlFx surfaces is the key factor for attachment of OTS, where the Al−F surface bond is hydrolyzed to form Al−O−Si link with OTS. Infrared absorption data indicate that a dense Si−O−Si network is formed above the AlFx surfaces upon attachment of OTS. Based on the optical modeling of ν(CH2) absorption bands, an average tilt angle of the molecular layer on fluorinated aluminum is estimated to be 27° ± 2° to the surface normal. Owing to the high packing of the grafted OTS layer, the modified surfaces exhibit an excellent hydrophobicity with a contact angle of 105°. The aging and stability of the interface are determined using X-ray photoelectron spectroscopy.