AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS1+NS-MoA

Invited Paper SS1+NS-MoA3
Calorimetric Measurements of Metal Adsorption and Adhesion Energies on Clean, Single-Crystalline Surfaces

Monday, November 2, 1998, 2:40 pm, Room 308

Session: Novel Surface Probes
Presenter: C.T. Campbell, University of Washington
Authors: C.T. Campbell, University of Washington
J.T. Stuckless, University of Washington
D.J. Bald, University of Washington
D.E. Starr, University of Washington
J.E. Musgrove, University of Washington
Correspondent: Click to Email
The adsorption and adhesion energies of metals on solids are important in many materials and chemistry applications including oxide-supported metal catalysts, bimetallic catalysts, epitaxial thin film growth, metal-ceramic interfaces in microelectronics, metalization of polymers, composite materials and metal adsorption on minerals in soils. The heats of adsorption of metals have been measured calorimetrically for the first time on clean, single-crystalline surfaces. A pulse of metal vapor from a chopped atomic beam adsorbs onto an ultrathin single crystal's surface in ultrahigh vacuum, causing a transient temperature rise. This heat input is detected by a pyroelectric polymer ribbon, which is gently touched to the back of the crystal during calorimetry. The sticking probability is measured by detecting the reflected fraction mass spectrometrically with a line-of-sight modification of the King and Well's method. The differential heat of adsorption is thus measured as a detailed function of coverage up through multilayer coverages. The integral heat of adsorption also provides the adhesion energy of the metal film, if the surface free energy of the clean metal surface is known. Adsorption and adhesion energies for metals (Pb or Cu) on the clean Mo(100) surface, on well-defined surface oxides of Mo(100) and W(100), and on clean and hydroxylated MgO(100) thin films will be reported. By comparing a variety of surfaces in Pb and Cu adsorption, an interesting correlation between the growth morphology of thin metal films and the initial heat of adsorption of the metal is revealed. The sticking probability also correlates with the heat of adsorption of the metal.