Study of self-limiting oxidation of silicon nanoclusters by atomistic simulations

Abstract

We present molecular dynamics simulations directed at understanding self-limiting oxidation of nanoclusters. Atomic oxygen is inserted in an atom-by-atom way in the silicon bonds to form silicon oxide. First, we focus on planar oxidation to calibrate our model and test its capabilities. Then, we present results on oxidation of 50 Å diam silicon spheres. Kinetic causes of self-limitation are investigated by drawing a map of the local stress in the Si/SiO 2 system. We obtain stresses in contrast to in continuum models. For thin oxides, we find in particular tensile pressure in the silicon core and a pressure gradient in the oxide shell. We investigate the effect of pressure gradient on the O 2 transport within the framework of Nerst-Eintein's transport equation. We find that a pressure gradient compatible with experimental estimates yields self-limitation of the oxidation kinetics.

Synchrotron radiation x-ray photoelectron spectroscopy of Si nanocrystals grown onto Al2O3∕Si surfaces

“…As the escape depth of the Si 2p photoelectrons at the photon energy used here does not exceed 1 nm ͑well below the mean radius of the NCs if͒, the main contribution to the Si 0 signal should then arise from the disordered Si atoms close to the core/shell interface. The second cause of structural disorder in the NCs is the level of inhomogeneous stress from the core to the oxidized shell surface, as shown by Dalla Torre's calculations 22 on the oxidation of 5 nm diameter Si NCs, in agreement with previous electron microscopy results. 17 The stressed silica shell may have considerable density and therefore structural differences with respect to planar silica.…”

Characteristics of mechanically milled silicon nanocrystals embedded in TEOS thin films

“…This suggests that the interfacial strain is capable of creating NBOHC in the structure of milled Si nc/SiO 2 systems. Simulation of increasing strain in the interface due to long oxidation hours between the Si nc and SiO 2 matrix has also been demonstrated [11] and this should increase the amount of NBOHC [6]. However, Fig.…”

Understanding the mechanism of aluminium nanoparticle oxidation

“…The phenomenological model for mass transport in the coated nanoparticle recently proposed by Dalla Torre et al [27] for silicon has been extended here to describe the oxidation of aluminium nanoparticles with a pressure gradient present within the particle.…”

“…where P is the pressure gradient in the particle, V O is the solubility volume of oxygen in aluminium oxide, taken to be 0.02 nm 3 based on work of Dalla Torre et al [27], and T is the temperature of particle. This relation can be thought of as an Einstein's relation for diffusion, D = k B T × v F .…”