Near edge x-ray absorption spectroscopy: a novel approach for determining conduction band edge states in transition metal oxide gate dielectrics

Abstract

Spectroscopic studies of transition metal (Tm) and rare earth (Re) oxides, combined with ab initio theory identify the band edge electronic structure of alternative high-K dielectrics. The lowest conduction band states are derived from antibonding transition metal d*-states with a π symmetry and show strong final state effects. Applied to the complex Tm/Re mixed oxides of the general form ReTmO3, this approach identifies a novel way for obtaining separate and independent control of band gap energies and dielectric constants through local bonding arrangements in which Tm and Re atoms are nearest neighbors to the same oxygen atom.