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

摘要

It is shown that a two-component percolation model can explain anexperimentally observed behavior, namely that a network built up by a mixtureof sintered nanocrystalline semiconducting n- and p-grains can exhibitselective behavior, i.e. respond with a resistance increase when exposed to areducing gas A and with a resistance decrease in response to another reducinggas B. To this end, a simple model is developed based on realistic assumptionsabout the reactions on the grain surfaces. The resistance is calculated byrandom walk simulations with nn-, pp- and np-bonds between the grains and theresults are found in very good agreement with the experiments. Contrary toformer assumptions, the np-bonds are crucial to obtain this accordance.