The morphology and formation mechanism of aluminum nitride nanocrystals synthesized by chemical vapor deposition

Nanocrystal aluminum nitride (AIN) powders were obtained by the chemical va por deposition (CVD) process via the AICl(3)-NH3-N-2 system at 1323 K with various total flow rates. The morphology and formation mechanism of the syn thesized AIN powders were characterized by X-ray diffraction (XRD) and tran smission electron microscopy (TEM). It has been shown that all of the obtai ned powders exclusively belong to the single-phase AlN and do not depend on the variation of the total flow rate of the 1 : 1 molar ratio of the gas m ixture of NH3/N-2. On the other hand, the crystal shapes were affected by t he position of the entry/mixing of the reacting gases of AlCl3 and NH3. The average crystal size of the AIN powders was decreased from 35.0 to 12.5 nm as the gas-mixture flow rates were increased from 200 to 800 cm(3)/min. A crystal growth model of the AIN powders has been proposed for the stages of the adsorption/desorption rates in the inlet zone of the reacting gases -- > AlN formation --> crystal growth --> crystal agglomeration. (C) 2000 Else vier Science B.V. All rights reserved.