SUBSTITUTIONAL ADSORPTION OF K ON FE(100)

The adsorption of potassium on Fe(100) was studied by time-of-flight f orward scattering and recoiling spectroscopy (TOF-SARS), low energy el ectron diffraction (LEED) and Auger electron spectroscopy (AES). After heating to 650 K of the potassium saturated surface the formation of a p(3 x 3) potassium superstructure was observed by LEED. TOF-SARS exp eriments ruled out the adsorption of potassium in the on-top, bridge a nd four-fold hollow site. The only site which is in agreement with all experimental results is the substitutional site where K replaces an F e atom of the topmost layer of the crystal. This is the first time a s ubstitutional adsorption site has been found on a bcc surface. On an f cc surface such an adsorption site has been found recently for adsorpt ion of sodium and potassium on Al(111).