An original integrated approach developed within a multiscale strategy, which combines first-principles quantum simulations and kinetic Monte Carlo (KMC), is presented to investigate the atomic layer deposition (ALD) of HfO2 on Si(100) surface. Density functional theory within the hybrid functional is used to determine the detailed physicochemical mechanisms and associated energetics of the two half cycles taking place during the initial stage of film growth. A kinetic Monte Carlo model is then proposed that deals with the stochastic nature of the calculated DFT mechanisms and barriers. Beyond the chemical information emanating from DFT calculations, the lattice-based KMC approach requires preliminary physical considerations issued from the crystal structures that the system is intended to adopt. This is especially critical in the case of heterogeneous systems like oxides deposited on silicon. We also describe (i) how atomistic configuration changes are performed as a result of local events consisting in elementary reaction mechanisms occurring on specific lattice sites, (ii) the temporal dynamics, governed by transition probabilities, calculated for every event from DFT activation barriers, and (iii) the relation of KMC with the ALD experimental procedure. Some preliminary validation results of the whole multiscale strategy are given for illustration and pertinence with regard of the technological main issues.

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Using density functional theory calculations, we address the structural phase transition from the covalent metallic precursor molecules to their oxide layer structure during the gas-phase deposition process. We observe that the associated increase in the metal coordination number during the gas–solid transition, i.e., the redistribution mechanisms of oxygen atoms around the metal atoms, are identical and barrierless for Sn- or Hf-based precursors. These mechanisms, occurring in the grown oxide layers, are shown to be present at the early stage of gas phase agglomeration reactions, giving rise to unexpected species. The presence of OH hydroxyl groups on the surface/hydroxylated precursors are mainly responsible for this transition. Finally, we discuss the relevance of our calculations within the framework of the metal oxides growth by ALD process.

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From a detailed analysis of density-functional calculations on gold model clusters and surfaces, an empirical potential for gold, which includes angular corrections, is derived. This potential introduces higher-order nonlinear terms ͑specifically, the product dipole-quadrupole͒ that do not seem to have been previously used, but that are necessary to describe directionality effects in the gold-gold interaction. Preliminary tests show that the proposed empirical potential possesses novel features with respect to the existing ones, such as a strong tendency of small Au clusters toward cage configurations, and represents a good starting point for future investigations.

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