Defect state features were detected in second derivative O K edge spectra for thin

films of nano-crystalline TiO2 and HfO2. Based on soft X-ray photoelectron band

edge spectra, and the occurrence of occupied band edge 4f states in Gd(Sc,Ti)O3,

complementary spectroscopic features were confirmed in the pre-edge (<530eV)

and vacuum continuum (>545eV) regimes of OK edge spectra. Qualitatively similar spectral features were obtained for thin films of HfO2 and TiO2, and these

were assigned to defect states associated with vacancies. The two

electrons/removed O-atom were not distributed uniformly over the TM atoms

defining the vacancy geometry, but instead were localized in equivalent d-states: a

d2 state for a Ti monovacancy and a d4 state for a Hf divacancy. This new model

for electronic structure provides an unambiguous way to differentiate between

monovacancy and divacancy arrangements, as well as immobile (or fixed) and

mobile vacancies.

Spectroscopic Differentiation Between O-Atom Vacancy and Divacancy Defects,

Respectively, in TiO2 and HfO2 by X-Ray Absorption Spectroscopy. G.Lucovsky,

K.B.Chung, J.W.Kim, D.Norlund: Microelectronic Engineering, 2009, 86[7-9],

1676-9