Analysis of the extended defects in 3C-SiC.pdf - Nelson Mandela ...

2.2.2 The Zinc-Blende Structure
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The zinc-blende structure can be seen as composed of a basic fcc framework with
atoms situated at positions as discussed above, with the addition of a further set of
1 1
atoms situated at positions 4 4 4
1 3 1 1 3 1 3
3 3
; 4 4 4 ; 4 4 4 and 4 4 4
3 . The two sets of atoms may be
of the same type as for example in diamond (carbon), silicon, germanium or it may
consist of a composition of different elements such as for GaAs, ZnS and SiC. The
unit cell consists of 8 atoms and can be seen as two interpenetrating fcc lattices
a
displaced by a translation of 111 as shown in Fig. 2.3.
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Fig. 2.3. The SiC zinc-blende unit cell with the smaller atoms being the carbon and
the larger silicon.
The stacking sequence of the zinc-blende structure for the {100}, {110} and {111}
planes are analogous to that of the fcc-structure with the only difference being that the
two sets of atoms create a doubling of the stacking sequence in the sense that in the
{100} and {110} cases one obtains a sequence AA'BB'AA'… and in the {111} a
sequence AA'BB'CC'… is seen (where the ' denotes the alternate set). This is shown
in Fig. 2.4 for the stacking of the {100} and {111} planes.