Abstract
The reaction mechanisms between Titanium(IV) isopropoxide (TTIP), Titanium(IV) methoxide
14 [Ti(OCH3)4] as titanium precursors and water as oxygen agent respectively, were investigated. Atomic
15 layer deposition (ALD)–TiO₂ thin film deposition process was assumed focusing on their molecular
16 dynamics through interaction with hydroxyl molecule and titanium organic bonds. Based on the
17 computational results obtained by performing the density functional theory (DFT) calculations, the
18 sequence of bonds formation and interaction in these precursor molecules during their reaction with water
19 align with the adsorption mechanism on the Si(100) surface. The differences in the relative energy at each
20 stage of the reaction allow their comparison in terms of the reaction rate and process temperature. When
21 interacted with the H2O molecule, the ligands of TTIP and Ti(OCH₃)₄ molecules dissociate with average
22 activation barriers of 15.9 and 14.5 kcal/mol, respectively, indicating that Ti(OCH₃)₄ can undergo
23 decomposition at lower temperatures compared to TTIP. This observation aligns with the adsorption
24 behavior of TTIP and Ti(OCH₃)₄ molecules on hydroxylated Si(100) surfaces, which exhibit activation
25 barriers of 13.4 and 11.5 kcal/mol, respectively. These findings support the hypothesis that precursor
26 molecules with lower decomposition barriers tend to adsorb more readily onto substrate surfaces and
27 generally require lower process temperatures. These insights enabled us to predict the adsorption
28 mechanisms of these titanium precursors based on their interactions with water molecules. Based on
29 molecular behavior, it should provide a framework for the reaction mechanisms of various precursors on
30 different substrate surfaces for producing a broad range of ALD metal oxide thin films.