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.

Oxidation mechanism of aluminum nitride revisited

“…Prior to the oxidation treatments, the substrate was heat treated at 500 ℃ for 4 h in air. This temperature was high enough to remove any organics, and low enough to induce noticeable oxidation [7,8,11,16]. The oxidation was carried out in a tube furnace.…”

“…Previous studies mainly measured weight gain during oxidation [7][8][9][10][11][13][14][15][16]. The weight increase after oxidation of AlN bulk at lower temperature is very small, which may result in uncertainty in the measurement.…”

“…The weight increase after oxidation of AlN bulk at lower temperature is very small, which may result in uncertainty in the measurement. Some research groups thus have investigated the oxidation of AlN powder [8,10,14,16]. Weight gain is indeed larger for the powder; however, the oxidation starts at lower temperature and the corresponding activation energy is also lower (see Table 1).…”

“…The reaction process usually takes place at lower temperature. For AlN powder, the reaction process is found during oxidation in temperatures ranging from 550 to 1100 ℃ [8,10,14,16]. For bulk specimens, the reaction process is found in the temperature interval from 1000 to 1390 ℃ [7,9,[11][12][13]15].…”

“…The mechanism for the oxidation of AlN has been examined in many studies [7][8][9][10][11][12][13][14][15][16]. Previous studies mainly measured weight gain during oxidation [7][8][9][10][11][13][14][15][16].…”