ADSORPTION AND DESORPTION OF H2O ON POTASSIUM PRECOVERED SI(100)2X1 SURFACE

The adsorption and desorption of H2O on a potassium precovered Si(100) 2 x 1 surface have been studied using MDS (metastable deexcitation spe ctroscopy) and TDS (thermal desorption spectroscopy). It is concluded that H2O is dissociatively attached to a 1 ML K/Si(100)2 x 1 surface a s OH and H at a dosing less than 1 langmuir at room temperature, becau se no molecularly adsorbed H2O is observed either by MDS or by TDS. Th e thermal desorption spectrum of H-2 (mass 2) consists of two peaks. T he lower temperature peak at 140-degrees-C is attributed to the hydrog en of a OH species bound to a Si atom. The higher temperature peak at 510-degrees-C is caused by hydrogen bound to Si dangling bonds. The th ermal desorption spectrum of SiO (mass 44) has two peaks. The SiO deso rption peak at 280-degrees-C suggests that bonds weaker than the usual SiO2 bonds exist. A detailed description of the adsorption and desorp tion of H2O is given by comparing both spectra of MDS and TDS and a mo del is proposed.