Plasma-Enhanced CVD Synthesis and Structural Characterization of Ta2N3

Microcrystalline tantalum nitride films were prepared on various substrates from TaCl5 precursor and nitrogen gas using the plasma‐enhanced chemical vapor deposition (PECVD) method. Syntheses carried out at 600−650 °C led to single‐phase samples of the tantalum nitride Ta2N3 with a defect fluorite‐type structure. The anion vacancies were found to order resulting in a 2 × 2 × 2 cubic superstructure of the C‐Ln2O3 type (space group Ia$\bar 3$ , Z = 16) with a = 9.8205(4) Å according to a Rietveld refinement of the X‐ray powder diffraction data. At higher deposition temperatures (650−700 °C) formation of highly textured orthorhombic Ta3N5 was observed. The samples were additionally studied by high‐resolution transmission electron microscopy (HRTEM) and selected‐area electron diffraction (SAED). The details of the new crystal structure for Ta2N3 as well as a possible nitrogen nonstoichiometry are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)