Crystallization of Amorphous Diamond
(a) How does amorphous Diamond crystallize? Show the mechanism with a seed crystal.(b) How does the amorphous diamond crystallize on Silicon substrate?
adesh.zip
:Click HERE to Download a DEMO version of ADESHADESH works on PC-DOS. You will need the pkunzip.exe utility for this zipped file. ADESH works on MAC and UNIX workstations in a DOS window.
Answer
ADESH produced following results in a few hours, on a PC with a Pentium (P5-133) micro-processor.
Figure 1
Cluster of amorphous diamond atoms.
(a) Figure 1 shows the atomistic configuration
of a Diamond cluster of 275 atoms. The disorder seen is
indicative that it is amorphous. There is a small crystalline seed of
about 50 atoms in the center of this roughly spherical cluster.
When this custer was relaxed with Simulated Annealing
technique (Using ADESH Software package), the atoms arranged
to grow the inside crystal.
Figure 2 Crystallized diamond atoms with free surface reconstructions
Figure 2 shows a crystallized cluster. When the atom movements were
studied, it was clear that the crystal grew from the seed.
Substantial crystallinity was observed around 700K. The
relaxation was performed with free surface boundary conditions.
Hence some free surface atoms show rearrangements of atoms
and show slight deviation from their perfect crystalline positions.
Figure 3: Amorphous Diamond film on Silicon Substrate
A cross-section of amorphous diamond film on silicon substrate. One bottom layer of diamond was held fixed before amorphising the rest of the film. This configuration was relaxed with Simulated annealing techniques and free surface boundary conditions.
Figure 4: Crstallized Dimanond Film on Silicon Substrate
The amorphous diamond film crystallized upwards from the substrate. The surfaces show deviation from crystallinity because of surface effects (reconstruction).
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