Preferential adsorption of thermally activated oxygen onto annealed polycrystalline diamond films studied by high resolution electron energy and X-ray photoelectron spectroscopies

摘要

In this work the amount of adsorbed oxygen and its chemical bonding configuration to diamond surface were investigated by X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HR-EELS), correspondingly. Hot filament chemical vapor deposited polycrystalline diamond films with sub-micron grain size have been exposed in situ to thermally activated atomic oxygen (AO) and annealed in ultra-high vacuum (UHV) in the range of 600-1000 ℃. XPS studies revealed that substantial oxidation of the diamond surface takes place at T_A > 800℃, most likely owing to partial hydrogen desorption occurring at this temperature. HR-EELS revealed that the main constituents of the surface after exposure to AO are saturated and unsaturated hydrocarbon species and oxygen-bonded fragments. Oxygen bonds to diamond surface in ether (C-O-C), peroxide (C-O-O-C), and carbonyl (C=O) bonding. HR-EELS features comparison of hydrogenated and oxygen exposed diamond surface as a function of thermal annealing suggests enhanced reactivity of hydrogenated diamond (111) facets as compared to (100) ones.