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It is a common finding that titanocene-derived precursors do not yield TiO(2) films in atomic layer deposition (ALD) with water. For instance, ALD with Ti(OMe)(4) and water gives 0.5 ?/cycle, while TiCp*(OMe)(3) does not show any growth (Me = CH(3), Cp* = C(5)(CH(3))(5)). From mass spectrometry we found that Ti(OMe)(4) occurs in the gas phase practically exclusively as a monomer. We then used first principles density functional theory (DFT) to model the ALD reaction sequence and find the reason for the difference in growth behaviour. Both precursors adsorb initially via hydrogen-bonding. The simulations reveal that the Cp* ligand of TiCp*(OMe)(3) lowers the Lewis acidity of the Ti centre and prevents its coordination to surface O ('densification') during both of the ALD pulses. The effect of Cp* on Ti seems to be both steric (full coordination sphere) and electronic (lower electrophilicity). This crucial step in the sequence of ALD reactions is therefore not possible in the case of TiCp*(OMe)(3) + H(2)O, which means that there is no deposition of TiO(2) films. 相似文献
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Beuzart-Plessis Raphal Chaudouard Pierre-Henri Zydor Micha 《Publications Mathématiques de L'IHéS》2022,135(1):183-336
Publications mathématiques de l'IHÉS - In this paper, we prove the Gan-Gross-Prasad conjecture and the Ichino-Ikeda conjecture for unitary groups $U_{n}\times U_{n+1}$ in all the... 相似文献
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