Spin-polarized metastable deexcitation spectroscopy study of potassium and oxygen adsorbed iron surfaces

The effects of potassium adsorption and exposure to oxygen on the spin polarization of electrons spilling toward a vacuum are investigated, respectively, for clean and for potassium (1 ML)-precovered (100) surfaces of iron films deposited on a MgO(100) substrate by means of spin-polarized metastable deexcitafion spectroscopy (SPMDS). The 4s-electrons of potassium on Fe(100) surfaces exhibit a positive (= negative spin polarization to the majority spin of the iron film) SPMDS asymmetry, (I-p - I-a)/(I-p + I-a), which is the same polarity as that at the Fermi level for the clean Fe(100) surfaces. The positive asymmetry decreases to zero with an increase in the potassium coverage up to I ML. For lightly oxidized K (I ML)/ Fe(100) surfaces, the asymmetry around the K 4s peak becomes negative, while the gross shape of a K 4s peak is unchanged in the SPMDS spectra. These results are discussed in conjunction with the characteristics of potassium adsorption and the oxygen position in coadsorbed surfaces.