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

High-resolution electron energy loss spectroscopy (HPEELs) and thermal desorption spectroscopy (TDS) are employed to study the interaction b etween oxygen and potassium on graphite in the coverage range up to 2. 5 monolayers and in the temperature range 160-800 K. Annealing gives r ise to a succession of different KO(x) complexes, partially induced by surface segregation of intercalated potassium. A vibrational excitati on at 39 meV is attributed to K2O formation, in agreement with a recen t interpretation of XPS and HREELs spectra of oxidized single-crystal potassium. Two vibrational excitations at 30-31 meV and 180 meV are te ntatively 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.