Hafnium oxide thin films with varying oxygen content were investigated with the goal of finding the optical signature of oxygen vacancies in the film structure. It was found that a reduction of oxygen content in the film leads to changes in both, structural and optical characteristics. Optical absorption spectroscopy, using nanoKelvin calorimetry, revealed an enhanced absorption in the near-ultraviolet (near-UV) and visible wavelength ranges for films with reduced oxygen content, which was attributed to mid-gap electronic states of oxygen vacancies. Absorption in the near-infrared was found to originate from structural defects other than oxygen vacancy. Luminescence generated by continuous-wave 355-nm laser excitation in e-beam films showed significant changes in the spectral profile with oxygen reduction and new band formation linked to oxygen vacancies. The luminescence from oxygen-vacancy states was found to have microsecond-scale lifetimes when compared with nanosecond-scale lifetimes of luminescence attributed to other structural film defects. Laser-damage testing using ultraviolet nanosecond and infrared femtosecond pulses showed a reduction of the damage threshold with increasing number of oxygen vacancies in hafnium oxide films.

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The dynamics of a strong barrier discharge is investigated analytically in the simplest model that still keeps the essential discharge features. It is shown that at high overvoltage, the discharge develops into the ionizing wave moving from the anode toward the cathode. The velocity of this wave is found to be controlled mainly by the charge production rate in the cathode fall region and can considerably exceed the characteristic ion velocity. The influence of the capacitor formed by the dielectric layers on the discharge dynamics is analyzed. It is shown that, depending on the magnitude of the capacitance, two qualitatively different charging regimes exist.