Bismuth tris(bis(trimethylsilyl)amide) Bi(N(SiMe3)2)3 (combined with Titanium methoxide Ti(OMe)4 as Ti source and H2O as O source), was applied
as Bi precursor for the growth of bismuth titanate thin films by ALD. Self-limited growth of Bi−Ti−O layers was achieved at a deposition temperature of 190 °C. As-deposited Bi−Ti−O films demonstrated surface morphologies atypical
for amorphous ALD films, possibly related to either partial Bi reduction or to weak ordering of Bi−Ti−O layers during growth. Either pyrochlore Bi2Ti2O7-type structures, mixtures of pyrochlore- and layered perovskite Bi4Ti3O12, or phase-pure Bi4Ti3O12
were obtained depending on the Bi/(Bi + Ti) ratio in the Bi−Ti−O films postannealed at 750°C. The formation of phase-pure Bi4Ti3O12 was favoured by growing slightly Bi-rich films. After post-annealing in O2 at 600°C, 51 nm thick Bi−Ti−O layers deposited on Pt/SiO2/Si substrates demonstrated remnant polarization Pr = 0.5 μC/cm2, coercive field Ec = 24 kV/cm and leakage current density <1 μA/cm2 (up to ±1.6 V applied
bias) [i]
[i] M. Vehkamäki, T. Hatanpää, M. Kemell, M. Ritala, M. Leskelä, Chem. Mater., 2006, 18 (16), pp 3883–3888, DOI: 10.1021/cm060966v, « Atomic Layer Deposition of Ferroelectric Bismuth Titanate Bi4Ti3O12 Thin Films », https://pubs.acs.org/doi/abs/10.1021/cm060966v