Metallic friction: the effect of molecular adsorbates

• Published in: Surface science 1998-07, Vol.409 (2), p.171-182
• Main Authors: McFadden, C.F, Gellman, A.J
• Format: Article
• Language: English
• Subjects: Alcohols; Condensed matter: structure, mechanical and thermal properties; Copper; Exact sciences and technology; Friction; Low index single crystal surfaces; Lubrication; Mechanical and acoustical properties; adhesion; Physics; Single crystal surfaces; Solid surfaces and solid-solid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thermal desorption spectroscopy; Tribology
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(98)00178-2

A novel ultrahigh vacuum (UHV) tribometer was used to study the tribological behavior of two Cu(111) surfaces modified by the adsorption of various molecular species (ethanol, butanol and heptafluorobutanol). Friction measurements were made at coverages ranging from submonolayer to several multilayers. These alcohols showed similar friction behavior as a function of coverage. At coverages below one monolayer, the surfaces were not well lubricated; the sliding behavior was stick–slip, and the friction coefficients were high. At coverages greater than one monolayer, the friction coefficient was significantly reduced and decreased monotonically with increasing coverage. The transition of sliding behavior from “stick–slip” to “slip” occurred in the coverage range of 2–7 ML. The friction coefficient continued to decrease with increasing coverage, reaching a limiting value only at coverages of several multilayers.