Synthesis, Characterization, and Materials Chemistry of Group 4 Silylimides

This paper focuses on the development of potential single source precursors for M–N–Si (M = Ti, Zr or Hf) thin films. The titanium, zirconium, and hafnium silylimides (Me2N)2MNSiR1R2R3 [R1 = R2 = R3 = Ph, M = Ti­(1), Zr (2), Hf (3); R1 = R2 = R3 = Et, M = Ti (4), Zr (5), Hf (6); R1 = R2 = Me, R3 = tBu, M = Ti (7), Zr (8), Hf (9); R1 = R2 = R3 = NMe2, M = Ti (10), Zr (11), Hf (12)] have been synthesized by the reaction of M­(NMe2)4 and R3R2R1SiNH2. All compounds are notably sensitive to air and moisture. Compounds 1, 2, 4, and 7–10 have been structurally characterized, and all are dimeric, with the general formula [M­(NMe2)2(μ-NSiR3)]2, in which the μ2-NSiR3 groups bridges two four-coordinate metal centers. The hafnium compound 3 possesses the same basic dimeric structure but shows additional incorporation of liberated HNMe2 bonded to one metal. Compounds 11 and 12 are also both dimeric but also incorporate additional μ2-NMe2 groups, which bridge Si and either Zr or Hf metal centers in the solid state. The Zr and Hf metal centers are both five-coordinated in these species. Aerosol-assisted CVD (AA-CVD) using 4–7 and 9–12 as precursors generates amorphous films containing M, N, Si, C, and O; the films are dominated by MO2 with smaller contributions from MN, MC and MSiON based on XPS binding energies.