Nanoscale dielectric properties of TiO₂ in SiO₂ nanocomposite deposited by hybrid PECVD method

Abstract

In this paper, nanocomposites (TiO2 in SiO2) are produced by an advanced hybrid aerosol-PECVD method based on direct liquid injection of a non-commercial colloidal solution in an O2 / hexamethyldisiloxane (HMDSO) low-pressure plasma. Dielectric properties are investigated at nanoscale using techniques derived from Atomic Force Microcopy in terms of relative dielectric permittivity, charge injection and transport. Results show that a concentration in TiO2 up to 14% by volume makes it possible to increase the relative dielectric permittivity up to 4.8 while maintaining the insulating properties of the silica matrix. For a TiO2 concentration in the range 15 – 37% by volume, the relative dielectric permittivity increases (up to 11 for 37% TiO2 by volume) and only few agglomerated nanoparticles lowering the insulating properties are observed. For TiO2 concentration above 40% by volume, the relative dielectric permittivity still increases but the quantity of agglomerated nanoparticles is very high, which greatly increases the charge transport dynamic and degrades the insulating properties. Finally, 37 % of TiO2 by volume in the SiO2 matrix appears to be the best compromise, between high dielectric permittivity and low leakage current for the MIM applications aimed.