ULTRADLD electron spectrometer with an Al Kα X-ray source (1486.6 eV) operated at 150 W. A pass energy of 160 eV and a step size of 1 eV were used for survey spectra. For high energy resolution spectra, a pass energy of 20 eV and a step size of 0.1 eV were used. Sample charging effects were eliminated by correcting the observed spectra with the C 1s BE value of 285.0 eV.