Atomistic Simulation of the Formation of Nanoporous Silica Films via Molecular Chemical Vapor Deposition on Nonporous Substrates

Abstract

To distinguish thin deposited film characteristics clearly from the influence of substrate morphological properties, the growth mechanism and the macroscale and nanoscale properties of nanoporous SiO(2) films deposited on nonporous silica (SiO(2)) substrates from chemical precursors Si(OH)(4) and TEOS (tetraethoxysilane) via low-pressure chemical vapor deposition are the primary targets of this study. This work employs a kinetic Monte Carlo (KMC) simulation method coupled to the Metropolis Monte Carlo method to relax the strained silica structure. The influence of the deposition temperature (473, 673, and 873 K) on the properties of the SiO(x) layers is addressed via analysis of the film growth rates, density profiles of the deposited thin films, pore size distributions, carbon depth profiles (with respect to TEOS), and voidage analysis for layers of different thicknesses (8-18 nm). A comparison of simulation with experimental results is also carried out.

Diffusion within Ultrathin, Dense Nanoporous Silica Films

“…Central to future work on this topic will be the determination of the process parameters which will ultimately enable precise control of the parameter, scriptl , which itself largely determines both the magnitude of the peak in Figures b and peak position relative to the membrane thickness. Density is clearly an important control variable; however, as shown in a recent study of the deposition of alkoxysilane precursors via chemical vapor deposition care should also be undertaken to ascertain the influence of the precursor, CVD reactor temperature, and precursor partial pressure. Process conditions clearly influence the magnitude of the percolation cluster size, scriptl , as may be inferred from the results reported by Araki et al Another element of control relates to the Fickian term involving D. Lowering the diffusivity significantly enhances the relative importance of the non-Fickian contribution and this may be achieved by controlling film density and/or by introducing varying levels of other ionic species into the silica film (see for example Altemose).…”

Porosity Development in Silica Particles during Polymerization: Effect of Solvent Reactivity and Precursor Concentration

“…These energies were later incorporated to develop reactive force fields to perform molecular dynamics (MD) simulations of atomic silica species. The reactive MD simulation is used to study the formation of smaller oligomers like dimer and trimers, whereas to observe the formation of a larger cluster, often, elevated-temperature conditions are used. − Advanced simulation techniques such as kinetic Monte Carlo (MC), , lattice MC, − reaction ensemble MC, − and replica-exchange parallel tempering , are used in the literature to study the self-assembly of larger clusters . Earlier studies were mainly focused on developing a robust force-field simulation methodology to investigate the polymerization event for substantial time and length scales.…”