Tribological Properties of Self-assembled Monolayers on Au, SiOx and Si Surfaces

Using interracial force microscopy (IFM), the tribological properties of self-assembled monolayer (SAM) on Si surfaces produced by a new chemical strategy are investigated and compared to those of classical SAM systems, which include alkanethiols on Au and alkylsilanes on SiO{sub x}. The new SAM films are prepared by depositing n-alkyl chains with OH-terminations onto Cl-terminated Si substrates. The chemical nature of the actual lubricating molecules, n-dodecyl, is kept constant in all three thin film systems for direct comparison and similarities and differences in tribological properties are observed. The adhesion strength is virtually identical for all three systems; however, frictional properties differ due to differences in film packing. Differences in the chemical bonds that attach the lubricant molecules to the substrate are also discussed as they influence variations in film wear and durability. It is demonstrated that the new SAM films are capable of controlling the friction and adhesion of Si surfaces as well as the classical SAMs in addition to providing a greater potential to be more reproducible and more durable