Synthesis, Characterization and Thermal Study of Divalent Germanium, Tin and Lead Triazenides for Atomic Layer Deposition
The number of M–N bonded divalent group 14 precursors suitable for atomic layer deposition is limited, in particular for Ge and Pb. A majority of the reported precursors are dicoordinated, with the only tetracoordinated example being the Sn(II) amidinate. No such Ge(II) and Pb(II) compounds have been demonstrated. Herein, we present tetracoordinated Ge(II), Sn(II) and Pb(II) complexes bearing two sets of the bidentate 1,3-di-tert-butyl triazenide ligands. These compounds are highly volatile and show ideal behavior by thermogravimetric analysis. However, they have unusual thermal properties and exhibit instability during sublimation. Interestingly, the instability is not only temperature dependent but also facilitated by reduced pressure. Using quantum-chemical density functional theory, a gas-phase decomposition pathway was mapped out. The pathway account for the unusual thermal behavior of the compounds and is supported by electron impact mass spectrometry data.