Chemisorption energy of hydrogen on silicon surfaces

The chemisorption energy of H₂ on Si(111)7×{}7 and Si(001)2×{}1 was determined from thermodynamic equilibrium experiments in an ultrahigh vacuum quartz apparatus at temperatures of 760 to 970 K. The obtained values of 1.7±{}0.2 eV for Si(111) and 1.9±{}0.3 eV for Si(001) correspond to Si--H bond energies of 3.1 and 3.2 eV, respectively. Hydrogen bonding with silicon surfaces is thus found to be considerably weaker than in silane molecules and homologous clusters.