Electrophysical response of thin-film titanium-containing nanocomposites based poly(p-xylylene) on change of the atmosphere

Resumo

The dependence of the conductivity of poly(p-xylylene)-based titanium-containing nanocomposites on the extent of adsorption of polar molecules from the atmosphere is observed, while nonpolar molecules induce no such changes. A relationship between the dipole moment of the adsorbate molecule and the sensitivity of the composite conductivity to its vapor is revealed. A composite with filler content near the percolation threshold shows the highest sensitivity to polar gases. A model is proposed to explain the change in the resistance upon vapor adsorption by the formation of a surface dipole. Since the investigated vapors are adsorbed as donors, their adsorption reduces the electron work function of the nanoparticles, thereby increasing the conductivity. The dielectric spectrum of a nanocomposite containing 2 vol % titanium dioxide is very closely approximated by the Cole–Cole and Maxwell–Wagner equations, whereas the frequency dependence of the electric modulus is close to that predicted by the Debye law.