Intrinsic band edge traps in nano-crystalline HfO2 gate dielectrics

Chemically pure thin films of HfO2, as well as other transition metal and rare earth elemental and complex oxides, e.g., LaScO3 and LaAlO3, are nanocrystalline as-deposited. The local bonding environments of the transition and rare earth atoms are distorted with respect to ideal octahedral or cubic bonding, and degeneracies of the respective band edge d-states are completely removed by Jahn-Teller (J-T) distortions. Spectroscopic studies have revealed these J-T term splittings, and also a band edge localized state which is assigned to an electronically-active bonding defect at nanocrystalline grain boundaries.