A New single-crystal adsorption calorimeter for determining metal adsorption and adhesion energies

摘要

A microcalorimeter for measuring adsorption heats on clean single-crystal surfaces is described. The principle is similar to that pioneered by David King's group: A pulse of gas from a molecular beam adsorbs on an ultrathin single crystal's surface, causing a measurable transient heat input and temperature rise. Our novel heat detector is a 9 um m pyroelectric polymer ribbon, which is mechanically driven to make a gentle mechanical / thermal contact to the back of the single- crystal sample during measurements. Advantages include use of thicker samples (>3 microns), sample preparation at very high temperatures, and measurements at 100 K. We have applied this to study the heats of adsorption of metals on clean, well-defined and single-crystalline oxide surfaces as a detailed function of coverage, from which we also extract the metal/ oxide adhesion energy. We obtain pulse-to-pulse standard deviations of <2