Thermal stability and reactivity of titanium halide precursors for the atomic layer deposition of TiO₂ on a Pt (111) surface

The atomic layer deposition (ALD) of ultrathin metal-oxide film on metal surfaces is an effective technique for protecting supported metal catalyst against sintering, leaching and coking thereby improving catalyst stability and durability. Although numerous studies have demonstrated the advantages of TiO2 overcoats in catalysis, the reactivity and thermal stabilities of TiO2 ALD precursors on metal surfaces is still relatively unexplored. In this work, density functional theory (DFT) was employed to investigate the reactivity and thermal stability of titanium halide-based precursors with emphasis on homoleptic TiF4, TiCl4 and TiI4 precursors. In conjunction with DFT, the automated enumeration tool and the bond-ligand dissociation automation tool in Schrodinger material science suite were employed to investigate and compare the thermal stability and reactivity of the precursors. The surface reactivity of these precursors on a bare and hydroxylated Pt surface was also investigated. The results obtained from the simulations were compared and correlated with available literature. The results reveal that thermal stability of the precursors is represented as TiF4>TiCl4>TiI4 by whereas the opposite is true for the reactivity TiF4<TiCl4<TiI4. Moreover, the thermal stability of all heteroleptic precursors is dependent on the number of Ti-F bonds, while the reactivity depends on the number of Ti-I bonds. However, TiCl4 provides a better balance between the two extremes when taking both thermal stability and surface reactivity into consideration.