“…UHV conditioning was performed in repeated cycles of Ar + sputtering (4 × 10 −3 Pa Ar, 2 kV, 3 μA/cm 2 , 15 min), oxygen annealing (7 × 10 −5 Pa O 2 , 523 K, 15 min), and UHV annealing (≤4 × 10 −8 Pa, 10 min) until the surface was stoichiometric by Auger (AES) and X-ray photoelectron (XPS) spectroscopies, and characteristic binding energies and peak shapes were achieved in XPS. This procedure is described in greater detail elsewhere [7,8]. Characteristic XPS peak shapes and surface stoichiometry were confirmed by comparison to a CoO(1 0 0) surface prepared by UHV cleavage.…”