The formation of heterostructures that combine a large surface area with high surface activity has attracted the attention of the scientific community due to the unique properties and applications of these heterostructures. In this work, we describe – at the atomic level – the full reaction mechanisms involved in the atomic layer deposition of a hybrid ZnO/CNT inorganic structure. First, the pristine CNTs are chemically activated with a carboxylic acid, a process unique to carbon materials. Diethylzinc (DEZ) and water are used as gas-phase precursors to form ZnO. Our findings show that DEZ is physically adsorbed on the CNTs during the exposure of the first precursor. The ligand-exchange to generate chemisorbed ethyl zinc on the O side of the COOH group needs to overcome an energy barrier of 0.06 eV. This is a very small energy if compared to the values (0.5–0.6 eV) obtained in previous studies for OH functionalized surfaces. The height of the barrier is associated with the CO side, which mediates the H proton's exchange from the OH group to the C₂H₅ ligand. Furthermore, upon exposure to the oxidizing agent (H₂O), ethyl zinc exchanges its last ligand as ethane, and it accepts a hydroxyl group through a self-limiting reaction with an energy barrier of 0.88 eV. Notice that the energy barrier of the second ligand-exchange is larger than of the first. We have also analyzed the effect in the saturation of the second precursor: as the quantity of water molecules increases, the long-range interactions tend to repel them. However, the energy barrier of the second ligand-exchange decreases from 1.53 eV to 0.88 eV for one and two water molecules, showing a clear dependence on the oxidizing agent. Non-covalent interactions are used as a tool to visualize the driving forces that take place during each partial reaction in real space. Our study points out the importance of using the right functionalization agent to achieve a controlled and conformal ALD growth at the initial steps of the formation of hybrid ZnO/CNT structures, as well as the role played by the oxidizing agent to lower the energy barrier on the second ALD step.

In the present work, we report on a theoretical-computational study of the growth mechanism of the TiO₂-Graphene nanohybrid by atomic layer deposition.

The synergy between graphene and ZnO in creating hybrid nanomaterials with novel properties of interest for the technological industry requires the development of processes and techniques that enable their precise production at the nanoscale. Therefore, understanding the atomic and molecular mechanisms that lead to their creation is imperative for controlling each involved step in their formation, enhancing their efficiency. This work sheds light on the first atomic layer half-cycle for the growth of ZnO on graphene with a hydroxyl-functionalized monovacancy. We performed quantum mechanical calculations, considering a trapping-mediated mechanism and diethylzinc (DEZ) as the precursor. The results suggest that neighboring hydroxyl groups facilitate DEZ adsorption and minimize the activation energy. This is linked to the role of hydroxyl groups in the formation of noncovalent interactions such as weak van der Waals and C–H···O and O–H···O hydrogen bonds, which stabilize the systems and facilitate the first partial reaction. By comparing the response in systems with one, two, and three hydroxyl groups, it was found that as these functional groups increased in quantity, the reactions were both thermodynamically and kinetically more favorable. Thus, it can be concluded that incorporating hydroxyl groups on graphene through pretreatment may considerably increase the initial growth rate of ZnO.