Recombination of oxygen atomic excited states produced by non-equilibrium RF plasma on different semiconductor materials: catalytic phenomena and modelling

The purpose of this work is the study of oxygen atoms recombination on type n or p oxide semiconductors with various gap energies. The oxygen atoms are produced by a non-equilibrium low pressure RF plasma tubular reactor. The pressure is between 100 and 200 Pa. The relative oxygen atom concentration and the recombination coefficient ((gamma)) were measured by actinometric optical emission spectroscopy (AOES). A plot of the (gamma) coefficient versus 1/T allows the determination of the activation energy recombination. The results for p-type semiconductors show an increase of the activation energy with the gap energy. The recombination coefficient increases as gap energy decreases. In the case of n-type semiconductors, the activation energy depends on the number of active sites. Hence, the recombination of oxygen atoms depends on the electronic properties of the oxide semiconductors. The simulation of recombination of oxygen atoms on the oxide semiconductors was performed with a kinetic model of 18 reaction including three gas–surface reactions, using the Chemkin Surface code. The calculated values of the recombination coefficient show a good agreement with the experimental results in the temperature range of 300–900 K and give a good prediction up to 1200 K.