Dielectric losses and ac conductivity of Si–LiNbO3 heterostructures grown by the RF magnetron sputtering method

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Abstract

Single-axis <0001> textured polycrystalline LiNbO3 films were grown on (001) Si substrates by the RF magnetron sputtering method. Dielectric losses that occur in the Si–LiNbO3 heterostructures are caused by the conductivity of the LiNbO3 films. Analysis of temperature and frequency dependence of ac conductivity in the frequency range f = 25/105 Hz has demonstrated that it is expressed by the power law σ(ω) = Aωs and is described in the framework of the correlated barrier-hopping model. Thermal annealing (TA) of the Si–LiNbO3 heterostructures causes an increase in the density of the localized states in the band gap of LiNbO3 from D = 7 × 1024 m−3 to D = 2 × 1025 m−3. The conduction mechanism is changed radically after TA and phonon-assisted tunneling influences ac conductivity at the frequency of up to 800 Hz. At high frequency (f > 800 Hz), dielectric relaxation predominates affecting frequency dependence σ(ω) on relaxation time τ = 6.6 × 10−5 s.