Evaluation of tin nitride (Sn₃N₄) via atomic layer deposition using novel volatile Sn precursors

Novel Sn precursors, Sn(tbip)₂, Sn(tbtp)₂, and Sn(tbta)₂, were synthesized and characterized using various analytical techniques and density functional theory calculations. These precursors contained cyclic amine ligands derived from iminopyrrolidine. X-ray crystallography revealed the formation of monomeric SnL₂ with distorted seesaw geometry. Thermogravimetric analysis demonstrated the exceptional volatility of all complexes. Sn(tbtp)₂ showed the lowest residual weight of 2.7% at 265 °C. Sn₃N₄ thin films were successfully synthesized using Sn(tbtp)₂ as the Sn precursor and NH₃ plasma. The precursor exhibited ideal characteristics for atomic layer deposition, with a saturated growth per cycle value of 1.9 Å cy^-1 and no need for incubation when the film was deposited at 150-225 °C. The indirect optical bandgap of the Sn₃N₄ film was approximately 1-1.2 eV, as determined through ultraviolet-visible spectroscopy. Therefore, this study suggests that the Sn₃N₄ thin films prepared using the newly synthesized Sn precursor are suitable for application in thin-film photovoltaic devices.