Role of terminal groups in aromatic molecules on the growth of Al2O3-based hybrid materials

Modelling the growth reaction pathways of zincone ALD/MLD hybrid thin films: a DFT study

ALD/MLD hybrid thin films can be fabricated by combining atomic layer deposition (ALD) and molecular layer deposition (MLD). Even though this deposition method has been extensively used experimentally, the computational work required to acquire the reaction paths during the thin film deposition process is still in dire demand. We investigated hybrid thin films consisting of diethyl zinc and either 4-aminophenol or hydroquinone using both gas-phase and surface reactions to gain extensive knowledge of the complex phenomena occurring during the process of hybrid thin film deposition. We used density functional theory (DFT) to obtain the activation energies of these kinetic-dependent deposition processes. Different processes of ethyl ligand removal as ethane were discovered, and we found that the hydroxyl group of 4-aminophenol was more reactive than the amino group in the migration of hydrogen to an ethyl ligand within a complicated branching reaction chain.

Role of titanium and organic precursors in molecular layer deposition of "titanicone" hybrid materials

The development of hybrid inorganic-organic films with well-controlled properties is important for many applications. Molecular layer deposition (MLD) allows the deposition of these hybrid films using sequential, self-limiting reactions, similar to atomic layer deposition (ALD). In this paper, we use first principles density functional theory (DFT) to investigate the growth mechanism of titanium-containing hybrid organic-inorganic MLD films, known as "titanicones". We investigate in detail the chemistry between the most common Ti precursors, namely titanium tetrachloride (TiCl₄) and tetrakis(dimethylamido)titanium (Ti(DMA)₄), and ethylene glycol (EG) and glycerol (GL) as the organic precursors. We analyse the impact of the substrate on the initial MLD reactions in titanicone film growth using three different surface models: anatase TiO₂, rutile TiO₂ and Al₂O₃. Calculated energetics show that while TiCl₄ is reactive towards the anatase and rutile TiO₂ surfaces, it is not reactive towards the Al₂O₃ surface. Ti(DMA)₄ is reactive towards all surfaces. This is attributed to the stronger Ti-Cl bonds in TiCl₄ compared to Ti-N bonds in Ti(DMA)₄. Ti(DMA)₄ also shows high reactivity to the organics compared to TiCl₄. Double reactions of EG and GL with the TiCl₃ species from TiCl₄ and TiDMA species from Ti(DMA)₄ are also explored to better understand the origin of the different thicknesses of EG-titanicone and GL-titanicone films observed in experimental work. We find that EG and GL coupled with TiCl₄ can orient in a flat lying configuration on anatase while on rutile, the preferred orientation is upright. When combined with Ti(DMA)₄, EG and GL prefer the flat lying configuration on all surfaces. This work shows that the choice of the surface and the metallic precursor has a major impact on the behaviour of organic species. DFT findings provide motivation to develop a low temperature rutile TiO₂/titanicone film suggesting that the desired film growth could be achieved.

Atomic / Molecular Layer Deposition of Cerium (III) Hybrid Thin Films using Rigid Organic Precursors

Atomic / molecular layer deposition (ALD/MLD) process for the fabrication of cerium-based metal-organic hybrid films is demonstrated for the first time. The highly reactive cerium (III) guanidinate precursor [Ce(dpdmg)3] was...