AES AND SIMS ANALYSIS OF POTASSIUM GRAPHITE SURFACES

Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS) were used to analyze graphite surfaces onto which potassium was deposited in ultrahigh vacuum. Advantage is taken of the different surface sensitivities of AES and SIMS to determine the location of potassium. At a deposition temperature of 310 K, potassium diffused into the graphite and apparently formed intercalation compounds. At elevated temperatures, the intercalation compounds decomposed and potassium diffused to the surface and desorbed. Oxygen exposure at 310 K, following potassium deposition at 310 K, also destabilized these intercalation compounds and caused potassium to diffuse to the surface. Thermal treatment of potassium/oxygen/graphite surfaces showed that a molecular K2O species formed near 700 K and decomposed above 950 K.