NANOSTRUCTURE AND LOCAL CHEMICAL-COMPOSITION OF ALN-SI3N4 LAYERS GROWN BY LPCVD

As potential anti-oxidation coatings, several AlN-Si3N4 codeposits hav e been grown by chemical vapour deposition at low pressure (LPCVD) in a vertical hot-wall reactor on silicon carbide (SIC) layers. Transmiss ion electron microscopy (TEM) studies have been performed in order to determine both the microstructure and local chemical composition of th ese deposits. It has been confirmed that the material consists of a mi xture of aluminium nitride (AlN) and silicon nitride (Si3N4) phases, w hose proportion and crystallization are strongly dependent on the reac tor temperature and the reactive flow. In particular, the size of the AIN crystals varies from several nanometres to several hundred nanomet res. In this last case, structural defects such as dislocation, stacki ng faults or grain boundaries have been characterized by high-resoluti on electron microscopy (HREM) imaging. (C) 1997 Elsevier Science S.A.