Comparison of H2O2 and H2O oxidations on TDMAT absorbed on silicon(100) surface during reaction step of ALD–TiO2 process: A DFT study

Atomic layer deposition (ALD) is a thin film technology with high potential in nano fabrication . There is industrial demand to produce an ALD–TiO 2 thin film using a low temperature process for applications of bending electronic devices and biomaterials. TDMAT has gained the most attention as a suitable titanium source to grow an ALD–TiO 2 film at extremely low temperatures. In this process, almost all published reports have focused on metal-oxide precursors. The current work investigates the effects of oxidizing agents . For the first time, a theoretical investigation was carried out on the oxidation of H 2 O 2 and H 2 O on TDMAT absorbed on a silicon (100) surface during the reaction step of the ALD–TiO 2 process. We simulated the oxidation process, which continued from the adsorption step of the ALD–TiO 2 process, where the TDMAT was used as a titanium precursor. The cluster of the Si 9 H 12 =O 2 =Ti[N(CH 3 )] 2 surface model was used to represent the remaining TDMAT molecule absorbed on the Si(100) substrate. The reaction mechanisms of H 2 O 2 oxidizing on this surface were evaluated based on their reaction pathways. The reaction pathway of H 2 O oxidizing on this surface was calculated at the same level to compare the effect of oxidizers. The DFT at the B3LYP 6–311 G+ (2d,p) and 6–31 G(d,p) theoretical levels were used to calculate the potential energy surface and to optimize the electronic structures in this process. It was found that the reaction mechanism depended on the nature of chemical bond dissociation within the oxidizer molecules during the oxidation process. In the oxidation of H 2 O 2 , the H 2 O 2 molecule contained O–O and O–H bonds, which were dissociated during the oxidation process, resulting in different product structures. Only the O–O bond dissociation pathway produced the TiO 2 structure. The two species of TDMAT ligands at the surface were completely oxidized using a single H 2 O 2 molecule. The H 2 O 2 oxidation produced more –OH groups (double) compared to H 2 O oxidation. In H 2 O oxidation, the H 2 O molecule contained only the O–H bond within its molecule and required activation energies significantly less than for all pathways of H 2 O 2 . The HOMO–LUMO properties and IR frequency characteristics (cm −1 ) of the plausible product structures were discussed. The results should be useful in guiding the selection of suitable precursors for use in the co–reactant system of the ALD–TiO 2 process.