Low-frequency divergence of the dielectric constant in metal-insulator nanocomposites with tunneling

Dielectric measurements were done on cosputtered metal-insulator nanocompos ite films with metal volume fraction above the metal-insulator transition, in the frequency range between 20 Hz and 30 MHz. At intermediate and high f requency, the dielectric function can be qualitatively described in terms o f the percolation theory. In the low-frequency region, we observe a sharp r elaxation-type increase of the real part of dielectric constant with decrea sing frequency, while the imaginary part is dominated by de conductivity. W e suggest that the low-frequency behavior may be due to a combination of me tallic and tunneling conduction in the system. [S0163-1829(98)51644-X].