The poisonous effect of alkali adatoms on Cl-2 sticking

Cl-2 sticking on alkali-covered Si(100) is activated by the incident energies, E(i), i.e., there is a potential barrier to sticking. To understand the origin of the activation barrier, scattering experiments are performed. The observed Cl-2 scattering is predominated by direct-inelastic scattering even for E(i) less than or equal to 0.1 eV, suggesting that the Cs adatoms play a role in making the physisorption potential shallow, or the gas-surface interaction potential repulsive. Pauli repulsion is proposed for the origin of this repulsive interaction.