Transmission electron microscopy studies of AlN deposits

AlN deposits, prepared by low-pressure chemical vapour deposition (LPCVD), with or without N2O addition in the source gases, have been examined by several complementary transmission electron microscopy (TEM) techniques, including electron diffraction (ED), high-resolution electron microscopy (HREM), electron energy loss and extended energy loss fine structure spectroscopies (EELS and EXELFS), to determine both the structures and local chemical compositions. The major differences between the compounds lie in the occurrence of micro- and nanostructural changes, as dendrites and extended defects. It is suggested that the observed structural changes are induced by oxygen impurities. The implications of the results for the interpretation of some physical properties of the compounds are discussed in terms of these changes.