Kinetics and initial stages of oxidation of aluminum nitride: Thermogravimetric analysis and x-ray photoelectron spectroscopy study

Abstract

The resistance of AlN powder to oxidation upon heat treatment in air is investigated using thermogravimetric analysis (TGA) and x-ray photoelectron spectroscopy (XPS). The results reveal that oxidation is initiated at temperatures above 700 °C. For temperatures between 750 and 900 °C, an intermediate oxidation state, which involves the formation of oxynitrides, is detected by XPS and only a linear increase in weight with time is observed with TGA. Oxynitride formation precedes the formation of aluminum oxide and the oxynitride layer persists forming an interfacial layer between oxide and nitride. At temperatures above 900 °C XPS indicated the formation of a thick oxide layer while TGA measurements showed a linear followed by a nonlinear increase in weight with time. These results suggest that the initial stage of oxidation is controlled by surface reactions followed by diffusion controlled oxidation. The activation energy for surface reaction and diffusion oxidation are 36 and 56 kcal/mol, respectively.