Enthalpies of adsorption of metal atoms on single-crystalline surfaces by microcalorimetry

The heats of adsorption of metal gas atoms onto single crystalline surfaces can be measured directly as a detailed function of coverage using a unique microcalorimeter. The development of this experimental apparatus and the results obtained from these experiments will be reviewed. The heat detection is performed with a highly sensitive pyroelectric polymer ribbon pressed into contact with the thin (1 μ m thick) single crystal sample, onto which pulses of a metal atom beam impinge. Heats of adsorption have been measured for pulses of gas containing a few per cent of a monolayer with a pulse-to-pulse standard deviation as low as 1.5 kJ · mol−1. The adhesion energy of multilayer metal films can be estimated from the integral enthalpy of adsorption.