Tris(dimethylamido) tert-butyl titanium Ti(NMe2)3(tBu) (M =) is orange oil with boiling point 80 "C/0.l Torr.
Characterisation: µ-Analysis: Calc. for TiN3C10H2,: N, 17.71; C, 50.63; H, 11.47. Found: N, 17.12; C, 50.02; H, 11.30.
'H NMR (C6D6, δ) 1.23 (s, 9H, C(CH3)3), 3.09 (s, 18H, N(CH3)2);
IR (neat, KBr, cm-1) 2930 b, 2870 b, 2830 b, 2780s, 2700 w, 1445 b, 1420 m, 1350 w, 1250 s, 1145 s, 1120 m, 1055m, 940 s, 790 m, 590 s.
Synthesis: Ti(NMe2)4 / hexane (6.18 mmol) was mixed with LitBu/hexane (7.14 mmol) at 0°C. After warming to RT, the mixture was filtered, solvent evaporated, leaving dark orange oil. After vacuum distillation, Ti(NMe2)3(tBu) yield 60% was obtained.
The use tert-butyltitanium tris(dimethylamide) Ti(tBu)(NMe2)3 for TiN growth by APCVD was reported.[[i]] XPS revealed almost stoichiometric TiN with significant amounts of C and O. Nitrogen in films was Ti bound, while carbon was both Ti bound and organic. Precursor decomposition mechanisms were proposed involving both Ti-NR2 homolytic bond cleavage and amido ligand β-hydride activation, the latter accounting for the presence of Ti-bound carbon in the films. In support of this hypothesis, films made from precursors with cyclic amido ligands, for which β-hydride activation is disfavored, contained only organic carbon
Supported by the fact that carbon content TiN films was similar both in the case of TiN grown from Ti(NMe2)3(tBu) and Ti(NMe2)4, it was presumed that tBu group leaves cleanly from the precursor molecule, supporting two possible mechanisms:
1) Ti(NMe2)3(tBu) → TiH(NMe2)3 + Me2C=CH2 → Ti(NMe2)2 + HNMe2 (β-hydrogen elimination)
2) Ti(NMe2)3(tBu) → Ti(NMe2)3 + Me3C∙ ( homolytic Ti-CMe3 bond cleavage)
Further decomposition includes common species for different precursors containing NMe2 groups, probably Ti(NMe2)2, which was presumed to be a source of Ti-bound carbon in the films:
- titanium-bound carbon in the films
- Organic carbon is probably due to residual Ti-NR2 or Ti=NR fragments in the films
[i] R. M. Fix, R. G. Gordon and D. M. Hoffman, Chem. Mater., 2, (1990) 235.
Ti(NMe2)3(tBu) was applied as single source Ti/N/C precursor for the Ti(N,C,O) growth on glass and Si substrates by APCVD at growth temperature Tdep
300-400°C, precursor evaporation temperature Tprec 60°C, using N2 carrier (linear flow 1.4 m/min). Smooth adhererent Ti(N,C,O) films even at 300°C growth temperature were obtained, at growth rate ~22-25
nm/min. Ti(N,C,O) films were amorphous, according to XRD, their composition as per electronic microprobe was Ti0.20-0.24N0.22-0.27C0.29-0.36O0.29-O0.13, by XPS: Ti0.20-0.24N0.22-0.27C0.29-0.36O0.29-O0.13 [i]
[i] Bradley, D. C.; Thomas, I. M. J. Chem. Soc. 1960, 3857. (b) Bradley, D. C.; Torrible, E. G. Can. J. Chem. 1963, 41, 134.