THE INTERACTION OF POTASSIUM WITH OXYGEN ON GRAPHITE AS STUDIED BY HIGH-RESOLUTION ELECTRON-ENERGY-LOSS SPECTROSCOPY AND THERMAL-DESORPTION SPECTROSCOPY

High-resolution electron energy loss spectroscopy (HPEELs) and thermal desorption spectroscopy (TDS) are employed to study the interaction between oxygen and potassium on graphite in the coverage range up to 2.5 monolayers and in the temperature range 160-800 K. Annealing gives rise to a succession of different KO(x) complexes, partially induced by surface segregation of intercalated potassium. A vibrational excitation at 39 meV is attributed to K2O formation, in agreement with a recent interpretation of XPS and HREELs spectra of oxidized single-crystal potassium. Two vibrational excitations at 30-31 meV and 180 meV are tentatively attributed to either KO2 or K2O2. A high-temperature complex, which is an unidentified precursor to CO2 formation/desorption, has a single electron energy loss at 27 meV.