Modeling particle formation during low-pressure silane oxidation: Detailed chemical kinetics and aerosol dynamics

Abstract

Articles you may be interested inComplete thermodynamically consistent kinetic model of particle nucleation and growth: Numerical study of the applicability of the classical theory of homogeneous nucleation Process sensing and metrology in gate oxide growth by rapid thermal chemical vapor deposition from SiH 4 and N 2 O Characterization of fluorinated tetra ethyl ortho silicate oxide films deposited in a low pressure plasma enhanced chemical vapor deposition reactor A detailed chemical kinetic model is presented for silicon oxide clustering that leads to particle nucleation during low-pressure silane oxidation. Quantum Rice-Ramsperger-Kassel theory was applied to an existing high-pressure silane oxidation mechanism to obtain estimates for the pressure dependence of rate parameters. Four classes of clustering pathways were considered based on current knowledge of reaction kinetics and cluster properties in the Si-H-O system. The species conservation equations and a moment-type aerosol dynamics model were formulated for a batch reactor undergoing homogeneous nucleation and particle growth by surface reactions and coagulation. The chemical kinetics model was coupled to the aerosol dynamics model, and time-dependent zero-dimensional simulations were conducted. The effects of pressure and temperature were examined, and the main contributing processes to particle formation and growth were assessed, for conditions around 0.8 Torr, 773 K, and an initial oxygen-to-silane ratio of 15.

Implementation of a discrete nodal model to probe the effect of size-dependent surface tension on nanoparticle formation and growth

“…Thus, to be able to solve the problem with a size-dependent surface tension the nuclei formation rate must be computed from a model based on reversible chemical reaction processes driven by free energies as opposed to using a single nucleation rate expression. One approach that has been applied is to use the infrastructure of detailed chemical kinetics (Suh, Zachariah, & Girshick, 2001). However, such an approach while quite useful for what is essentially a gas-phase polymerization process is unrealistically complex for a system such as a metal nucleation.…”

“…Furthermore, such approaches inevitably must make an arbitrary jump between the molecular clusters treated in the formalism of chemical kinetics and the larger structures treated in the context of aerosol dynamics. For example in our work on silica particle formation (Suh et al, 2001) we truncated the kinetic simulation at a cluster size of (SiO) 10 because of computational tractability and the lack of high quality thermodynamic data. In this paper we will treat the nucleation as a continuum of chemical kinetic processes, which effectively will involve solution of the GDE with variable surface tension.…”

Nanoparticle coagulation in a planar jet via moment method

“…The source termω M k in Eq. (9), representing the contribution of the Brownian coagulation caused by the particle-particle interactions, is expressed as [22] …”

Image Analysis and Computer Simulation of Nanoparticle Clustering in Combustion Systems

“…Approximate solution methods are commonly applied to solve the ADE in order to span a larger range of particle sizes. The most common approximate solution methods are based on moment and sectional models (Wu and Flagan 1988;Zachariah and Semerjian 1989;Landgrebe and Pratsinis 1990;Pratsinis 1991, 1993;Pope and Howard 1997;Suh et al 2001;Mueller et al 2009). The moment method is typically applied while invoking assumptions regarding the size distribution of the particles where either a log-normal or a self-preserving profile is typically used.…”

“…The modeling approach and theory invoked are determined based on the size of the particles under consideration. For example, the early growth process (forming clusters of <10 atoms or molecules) has been modeled as polymerization of monomers using approximations and theory indicated by comparison with gas-phase reactions, e.g., Suh et al (2001) ab initio molecular orbital and reaction rate theory Tsang 1993, 1994). For collisions between larger clusters (e.g., consisting of 10 to 100s of atoms), classical molecular dynamics is often applied (Blaisten-Barojas and Zachariah 1992; Zachariah et al 1994aZachariah et al , 1994bZachariah and Carrier 1999;Hawa and Zachariah 2004;Lümmen and Kraska 2004).…”