Oxidation behavior of amorphous silicon nitride nanoparticles

Silicon oxynitride is a promising structural/functional material for high temperature applications. Silicon oxynitride can be synthesized through oxidation of amorphous silicon nitride (ASN) nanoparticles followed by a crystallization process. Oxidation of the ASN plays an important role during the synthesis. Here we investigated its oxidation mechanism in an atomic scale using experimental and modelling method. The results of Nitrogen-Oxygen analyzer and X-ray photoelectron spectroscopy indicate that a large amount of nitrogen vacancies exist in ASN, thus oxidation of ASN may include vacancy oxidation (oxygen atoms move into the nitrogen vacancies) and replacement oxidation (oxygen atoms replace nitrogen atoms). A model has been made to describe these two oxidation processes, from which the activation energy (E_a) of the vacancy oxidation and replacement oxidation is calculated to be 9.09 kJ/mol and 118.25 kJ/mol, respectively. These values agree well with E_a calculated from well-designed experiments, confirming the existence of the two different mechanisms during oxidation of ASN.