Plasma‐Enhanced CVD Synthesis and Structural Characterization of Ta 2 N 3

Microcrystalline tantalum nitride films were prepared on various substrates from TaCl 5 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 Ta 2 N 3 with a defect fluorite‐type structure. The anion vacancies were found to order resulting in a 2 × 2 × 2 cubic superstructure of the C‐Ln 2 O 3 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 Ta 3 N 5 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 Ta 2 N 3 as well as a possible nitrogen nonstoichiometry are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)