The real role of Cu metallic interlayer on the dielectric dispersion and conduction mechanism of TiO2/Cu/TiO2 nanolaminates

Abstract

In the present work, the effect of interference of highly transparent and conducting TiO2/Cu/TiO2 nanolaminated films with various Cu metallic interlayer thickness grown on Si (100) substrates by atomic layer deposition (ALD) and magnetron sputtering techniques on the dielectric properties and the AC conductivity of the as-prepared thin films, in the frequency range of 0.1–1000 kHz and in the temperature range of 300–393 K was investigated. The main goal of the studies performed was to compare the dielectric properties and the AC conductivity in two different Cu interlayer thicknesses (20 and 40 nm) and also to assess and relate the resulting properties with several experimental parameters. The AC conductivity measurements showed semiconducting behavior. The variation of the frequency exponent r has been explained in terms of different conduction mechanisms, the correlated barrier hopping (CBH), beside the quantum mechanical tunneling (QMT) models, depending on the Cu metallic interlayer thickness. It is found that the value of the maximum barrier height (Wm) decreases with increasing the Cu interlayer thickness and agree with that proposed by the theory of hopping of charge carriers. The study of the dielectric dispersion reveals that the Debye-type relaxation process was observed at the lower Cu interlayer thickness and fades as the Cu interlayer thickness increases. An observed decrease of dielectric loss with frequency downto low values indicates the suitability of the present samples for several energy storage applications. A new parameter related to the AC conductivity and dielectric constant ratio was studied and analyzed. The present outcome suggests that the thickness of the Cu metallic interlayer plays a vital role in the electric and dielectric properties of the films under investigation.