Spectroscopic Ellipsometry (SE) can be used for structure change observations in thin, (less than 10nm) HfO2 layers deposited by p-MOCVD on silicon substrate. The absorption edge Eg and most of the critical point transitions in HfO2 are above 6 eV, which makes the extension to Deep UV SE (5 to 9 eV) very suitable. The layer thickness can be deduced from the visible transparency range (where k~0). As a contrary, in the UV, the weak penetration of light enables to use a direct inversion method for n and k. It is shown that when the HfO2 thickness decreases below 3 nm, the analytical Tauc-Lorentz (TL) or Cody Lorentz models are no more applicable. The phase mixture changes as function of thickness and deposition process temperature, deduced from SE correspond well to XRD and Angle Resolved (AR)-XPS spectroscopy observations. From the absorption spectra at 4.5 eV, defects such as oxygen vacancies can be observed, whereas O/Hf ratio is estimated from XPS spectra. Deep UV SE reveals differences in the dielectric function with orthorhombic/monoclinic phase mixtures essentially with peaks at 7.5 and 8.5 eV. Quantum confinement originated from the grain size of the films and the excitonic origin of the 6 eV feature is discussed. see article here..\r\n
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Thick SiO2 on silicon substrate sample Ellipsometry data ( Experiments : SE UV Ellipsometer at LETI . (unpublished 2008)