Percolation model for a selective response of the resistance of composite semiconducting np-systems towards reducing gases

TL;DR

This paper presents a percolation model explaining the selective resistance response of composite semiconducting nanoparticle systems to different reducing gases, aligning well with experimental observations.

Contribution

It introduces a two-component percolation model that accounts for surface reactions and np-bonds, providing a new explanation for selective gas sensing behavior.

Findings

Model accurately reproduces experimental resistance changes.

np-bonds are essential for the observed selectivity.

Simulations match experimental data very well.

Abstract

It is shown that a two-component percolation model can explain an experimentally observed behavior, namely that a network built up by a mixture of sintered nanocrystalline semiconducting n- and p-grains can exhibit selective behavior, i.e. respond with a resistance increase when exposed to a reducing gas A and with a resistance decrease in response to another reducing gas B. To this end, a simple model is developed based on realistic assumptions about the reactions on the grain surfaces. The resistance is calculated by random walk simulations with nn-, pp- and np-bonds between the grains and the results are found in very good agreement with the experiments. Contrary to former assumptions, the np-bonds are crucial to obtain this accordance.