شبيه¬سازي ديناميك مولكولي واكنشي تشكيل نانولايه فروالكتريك HfO2 در غياب و در حضور ميدان الكتريكي

Reactive molecular dynamics simulation of the formation of ferroelectric HfO2 nanolayer in the absence an‎d presence of external field.

نانو فناوري

In this study, the nucleation an‎d growth mechanisms of TiO₂ an‎d HfO₂ nanolayers were investigated using Reactive Molecular Dynamics (RMD) simulations based on the ReaxFF force field. To analyze the behavior of the precursor species an‎d the underlying nucleation mechanisms, the Chemical Vapor Deposition (CVD) process was simulated for two gaseous systems, (TiCl₄, H₂O) an‎d (HfCl₄, H₂O), both in the presence an‎d absence of their respective substrates, TiO₂ an‎d HfO₂. In the absence of the substrate, three initial configurations were considered for the (TiCl₄, H₂O) system: a homogeneous gas mixture, separated gaseous species with a 2 Å gap, an‎d separated species with a 20 Å gap. The results revealed that for both gaseous systems, (TiCl₄, H₂O) an‎d (HfCl₄, H₂O), oxide clusters of TiO₂ an‎d HfO₂ were formed in the gas phase, indicating the onset of nucleation prior to surface interactions. In the presence of the substrate, three stoichiometric ratios were studied for each gaseous system, including the ideal, water-rich, an‎d water-deficient conditions. The simulations showed that the interaction of precursor species with the substrate surface led to adsorption, bond dissociation, an‎d subsequent layer growth. The results demonstrated that the nucleation an‎d growth mechanisms of titania an‎d hafnia nanolayers are strongly dependent on the molecular ratios of TiCl₄/H₂O an‎d HfCl₄/H₂O, exhibiting distinct reaction pathways an‎d bonding characteristics under different compositions. Furthermore, the effects of temperature an‎d external electric field on growth behavior an‎d structural stability were investigated. The findings revealed that the formation an‎d evolution of TiO₂ an‎d HfO₂ nuclei are governed by the initial configuration of gaseous components, temperature, an‎d the stoichiometric ratio of reactants. Analyses were conducted based on the radial distribution function (RDF), species population, total dipole moment, an‎d chemical composition of the surface layer. Overall, this study provides a comprehensive understan‎ding of the initial nucleation an‎d growth mechanisms in TiO₂ an‎d HfO₂ systems, offering valuable insights into atomic layer deposition (ALD) processes of chemically related oxide materials.

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