The growth and alloy formation of copper on the platinum (111) and stepped (553) crystal surfaces; characterization by Leed, AES, and CO thermal desorption

Abstract

Epitaxial layers of copper were formed on Pt(111) and Pt(553) single crystal surfaces by condensation of copper atoms from the vapor. Surface alloys were formed by diffusing the copper atoms into the platinum substrate at temperatures above 550 K. The activation energy for this process was found to be ~ 120 kJ mol . These Pt/Cu surfaces were characterized by LEED, AES, and TDS of CO. The copper grows in islands on the Pt(111) surface and one monolayer is completed before another begins. There is an apparent repulsive interaction between the copper atoms and the step sites of the Pt(553) surface which causes a second layer of copper to begin forming before the first layer is complete. Epitaxial copper atoms block CO adsorption sites on the platinum surface without affecting the CO desorption energy. When the copper is alloyed with the platinum however, the energy of desorption of CO from the platinum was reduced by as much as 20 kJ mol . This reduction in the desorption energy suggests an electronic modification that weakens the Pt-CO bond.