Daniel Mitchell, Nicole Bordes and Bernard Pailthorpe
Molecular Dynamics simulations
of carbon atom depositions are used to investigate energy diffusion
from the impact zone.
Simulations were performed of 50 eV carbon atom
depositions onto (111) surface of a 3.8nm x 3.4nm x 1.0nm
diamond slab containing 2816 atoms in 11 layers of 256 atoms each.
After the initial transient (200fSec) the impact zone has cooled below
3,000K then near 1,000K by 1pSec. Thereafter the temperature profile
decays approximately as described by diffusion
theory, perturbed by atomic scale fluctuations.
A continuum model of classical energy transfer is provided by the
traditionnal thermal diffusion equation.
The results show that continuum diffusion theory describes well energy diffusion in low energy atomic deposition processes, at distances and time scales larger than 1.5 nm and 1-2 pSec, beyond which the energy decays essentially exponentially.
1. 96
time steps.
Predictions of continuum diffusion theory are shown on the left and results of MD simulations on the right.
2. 56 time steps.
3. Different Views of Figure 2.
Profile of local temperatures for longer times (t>1.13pSec).Temperatures close to the point of impact have been removed to show the detail between 0.28 and 2.10 nm. The red mesh is the continuum Diffusion Theory.
Click here to see a quicktime animation showing how Figure 2 was extracted from Figure 1.
Click here to see a VRML model of this 3D graph.
Publication
B.A. Pailthorpe, D. Mitchell,
N. Bordes; "Thermal
Diffusion in Molecular Dynamics Simulations of Thin Film Diamond
Deposition"; Thin Solid Films,
332, pp 109-112 (1998).