Conducting transition metal nitride thin films with tailored cell sizes: The case of δ-TixTa1−xN

We present results on the stability and tailoring of the cell size of conducting δ-TixTa1−xN obtained by film growth and ab initio calculations. Despite the limited solubility of Ta in Ti, we show that TiN and TaN are soluble due to the hybrization of the d and sp electrons of the metal and N, respectively, that stabilizes the ternary system to the rocksalt structure. The stress-free cell sizes follow the Vegard’s rule; nevertheless, process-dependent stresses expand the cell size of the as-grown films. The electronic properties of δ-TixTa1−xN films (ρ=180Ωcm) are similar to those of TiN and TaN.