Observation of quantized subband states and evidence for surface electron accumulation in CdO from angle-resolved photoemission spectroscopy

The electronic structure of well-ordered single-crystal thin films of CdO(100) has been studied using angle-resolved photoemission spectroscopy. Quantized electron subbands are observed above the valence-band maximum. The existence of these states provides evidence of an intrinsic electron accumulation space-charge layer near the CdO surface, an interpretation supported by coupled Poisson-Schrodinger calculations. The origin of the accumulation layer result is discussed in terms of the bulk band structure of CdO calculated using quasiparticle-corrected density-functional theory, which reveals that the conduction-band minimum at the Brillouin-zone center lies below the charge neutrality level.