EPR characterization of defects in m-HfO2
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Electron Paramagnetic Resonance (EPR) measurements have been made on a variety of commercially available samples of powdered monoclinic HfO2. The high relative permittivity of HfO2 is one reason that it is being considered as a replacement for SiO2 as the gate dielectric in Si CMOS devices. The aim of the current measurements is to characterize the defects in HfO2. All EPR spectra were taken at a microwave frequency of about 9.5GHz and at room temperature. An axially symmetric spectrum with g// = 1.940 ± 0.003, g⊥ = 1.970 ± 0.002 is seen for all but one of the HfO2 samples; it is attributed to centres involving Hf3+ or Ti3+. Their average volume concentration varies from about 1017 cm−3 to less than 1014 cm−3 depending on the product specification and it is unaffected by γ-irradiation. Grinding granules to powder and/or γ-irradiation yields further EPR spectra that are likely to be associated with defects at or near the surface.