ac conduction and 1/f noise in a Cr-film lattice-percolation system

Abstract

The ac conductivity σ(ω), ac dielectric constant ε(ω), and (1/f)-noise spectral density Sv(f) have been studied in a Cr-film lattice-percolation system generated by electron-beam lithography. A power-law behavior, σ(ω)∝ωx and ε(ω)∝ω−y, is observed near the percolation threshold. The ac-conductivity and ac-dielectric-constant exponents x and y are found to be 0.98±0.09 and 0.08±0.04, respectively. While these results satisfy the general scaling law x+y=1 and are consistent with those previously obtained on Au-film continuum-percolation systems, they cannot be explained by present percolation theories applied to two-dimensional (2D) systems. The normalized (1/f)-noise spectral density Sv(f)/V2 is found to scale as Rw (where R is the sample resistance) with critical exponent w=1.18±0.19. Once again, the numerical value of w is appreciably different from the predictions of present percolation theories applied to 2D systems. We discuss the discrepancy between the experimental results and percolation theories.