Multiscale computational fluid dynamics modeling and reactor design of plasma-enhanced atomic layer deposition

Evaluation of tin nitride (Sn3N4) via atomic layer deposition using novel volatile Sn precursors

Novel Sn precursors, Sn(tbip)2, Sn(tbtp)2, and Sn(tbta)2, were synthesized and characterized using various analytical techniques and density functional theory calculations. These precursors contained cyclic amine ligands derived from iminopyrrolidine. X-ray crystallography revealed the formation of monomeric SnL2 with distorted seesaw geometry. Thermogravimetric analysis demonstrated the exceptional volatility of all complexes. Sn(tbtp)2 showed the lowest residual weight of 2.7% at 265 °C. Sn3N4 thin films were successfully synthesized using Sn(tbtp)2 as the Sn precursor and NH3 plasma. The precursor exhibited ideal characteristics for atomic layer deposition, with a saturated growth per cycle value of 1.9 Å cy-1 and no need for incubation when the film was deposited at 150-225 °C. The indirect optical bandgap of the Sn3N4 film was approximately 1-1.2 eV, as determined through ultraviolet-visible spectroscopy. Therefore, this study suggests that the Sn3N4 thin films prepared using the newly synthesized Sn precursor are suitable for application in thin-film photovoltaic devices.

Molecular Dynamics of Atomic Layer Deposition: Sticking Coefficient Investigation

This study focused on the atomic scale growth dynamics of amorphous Al2O3 films microscale structural relaxation. Classical Molecular Dynamics (MD) can not entirely model the challenging ALD dynamics due to the large timescales. The all-atom approach has rules based on deposition actions modelled MD relaxations that form as input to attain a single ALD cycle. MD relaxations are used to create a realistic equilibrium surface. This approach is fitting to this study as the investigation of the sticking coefficient is only at the first monolayer that includes the layering of a hydroxyl surface of alumina. The study provides insight between atomic-level numerical information and experimental measurements of the sticking coefficient related to the atomic layer deposition. The MD modeling was for the deposition of Al2O3, using trimethylaluminum (TMA) and water as precursors. The film thickness of 1.7 Å yields an initial sticking coefficient of TMA to be 4.257 × 10−3 determined from the slope of the leading front of the thickness profile at a substrate temperature of 573 K. This work adds to the knowledge of the kinetic nature of ALD at the atomic level. It provides quantitative information on the sticking coefficient during ALD.