Paramagnetic NO2 centers in thin γ-irradiated HfO2 layers on (100)Si revealed by electron spin resonance

Electron spin resonance (ESR) analysis reveals the incorporation of N in (100)Si/HfO2 structures with ultrathin amorphous HfO2 films deposited by chemical vapor deposition (CVD) using Hf(NO3)4 as precursor, through detection, after 60Co γ-irradiation, of NO2 radicals (density ≳55 at. ppm). The molecules are found to be stabilized and likely homogeneously distributed in the HfO2 network. Some network forming N entity is suggested as a precursor, transformed into ESR-active NO2 upon γ-irradiation. The interesting N incorporation aspect appears inherent to the particular CVD process.