In situ gravimetric monitoring of decomposition rate on the surface of (0001) c-plane sapphire for the high temperature growth of AlN

The thermal stability of (0001) sapphire was investigated at atmospheric pressure using the in situ gravimetric monitoring (GM) method. The weight change of a sapphire substrate was monitored at various hydrogen partial pressures in carrier gas (PH2) at temperatures over 1200 degrees C. Although the sapphire substrate was stable up to 1450 degrees C in an inert carrier gas (PH2 = 0.0 atm), sapphire decomposition started to occur at 1200 degrees C in H-2 carrier gas (PH2 = 1.0 atm). Moreover the activation energy and order of reaction for sapphire surface decomposition changed at approximately 1300 degrees C. These results indicate that the rate-limiting reaction for sapphire decomposition shifts near 1300 degrees C. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.