Influence of defects on the effective electrical conductivity of a monolayer produced by random sequential adsorption of linear $k$-mers onto a square lattice

TL;DR

This study uses Monte Carlo simulations to analyze how lattice and particle defects affect the electrical conductivity and percolation in monolayers formed by randomly depositing linear k-mers on a square lattice, considering both isotropic and anisotropic orientations.

Contribution

It provides new insights into the combined effects of lattice and particle defects on electrical conductivity and percolation thresholds in monolayers of linear k-mers, including phase diagrams for various defect concentrations.

Findings

Increasing defect concentrations reduces electrical conductivity.

Anisotropic deposition results in higher conductivity along the alignment direction.

Percolation is suppressed with higher defect levels, especially in anisotropic cases.

Abstract

The effect of defects on the behavior of electrical conductivity in a monolayer produced by the random sequential adsorption of linear $k$-mers (particles occupying $k$ adjacent sites) onto a square lattice is studied by means of a Monte Carlo simulation. The $k$-mers are deposited on the substrate until a jamming state is reached, i.e. a state where no one additional particle can be placed because the presented voids are too small or of inappropriate shapes. The presence of defects in the lattice (impurities) and of defects in the $k$-mers with concentrations of $d_l$ and $d_k$, respectively, is assumed. The defects in the lattice are distributed randomly before deposition and these lattice sites are forbidden for the deposition of $k$-mers. The defects on the $k$-mers are distributed randomly. The sites filled with $k$-mers have high electrical conductivity whereas the empty sites, and the sites filled by either types of defect have a low electrical conductivity, i.e., a high-contrast is assumed. We examined isotropic (both the possible orientations of a particle are equiprobable) and anisotropic (all particles are aligned along one given direction, $y$) deposition. To calculate the effective electrical conductivity, the monolayer was presented as a random resistor network (RRN) and the Frank--Lobb algorithm was used. The effects of the concentrations of defects $d_l$ and $d_k$ on the electrical conductivity for the values of $k = 2^n$, where $n =1,2,\dots, 5$, were studied. Increase of both the $d_l$ and $d_k$ parameters values resulted in decreases in the value of $\sigma$ and the suppression of percolation. Moreover, for anisotropic deposition the electrical conductivity along the $y$ direction was noticeably larger than in the perpendicular direction, $x$. Phase diagrams in the ($d_l, d_k$)-plane for different values of $k$ were obtained.