4.3 Dislocations
83
(a)
L
b
(b)
L
b
Fig. 4.15 Model of a an edge and b a screw dislocation. The line vector L and the Burger’s vector b are indicated
(a)
(b)
Fig. 4.16 a Atomic force microscopy image of growth spiral around a screw dislocation on a silicon surface; image
width: 4 µm. (textbfb STM image (width: 75 nm) of a screw-type dislocation with a Burgers vector of [000-1] on the
N-face of GaN. The reconstruction is c(6×12). The c(6×12) row directions correspond to ¯
1100. Reprinted with
permission from [322], ©1998 AVS
4.3.1.2 Screw Dislocations
For a screw dislocation (Fig. 4.15b) b and L are collinear. The solid has been cut along a half-plane up
to the dislocation line, shifted along L by the amount b and reattached.
Around the intersection of a screw dislocation with a surface, the epitaxial growth occurs, typically
in the form of a growth spiral that images the lattice planes around the defect.
4.3.1.3 60
◦ Dislocations
The most important dislocations in the zincblende lattice (Fig. 4.17) have the line vector along 110
With the Burger’s vector a/2 110 three different types of dislocations can be formed: edge, screw
and 60
◦ dislocations. The vicinity of the core of the latter is shown in more detail in Fig. 4.17d. We note
that the atomistic structure of 60
◦ dislocations is different for L along [110] and [−1 10]; depending
on whether the cations or anions are in the core, they are labeled α or β dislocations.
83
(a)
L
b
(b)
L
b
Fig. 4.15 Model of a an edge and b a screw dislocation. The line vector L and the Burger’s vector b are indicated
(a)
(b)
Fig. 4.16 a Atomic force microscopy image of growth spiral around a screw dislocation on a silicon surface; image
width: 4 µm. (textbfb STM image (width: 75 nm) of a screw-type dislocation with a Burgers vector of [000-1] on the
N-face of GaN. The reconstruction is c(6×12). The c(6×12) row directions correspond to ¯
1100. Reprinted with
permission from [322], ©1998 AVS
4.3.1.2 Screw Dislocations
For a screw dislocation (Fig. 4.15b) b and L are collinear. The solid has been cut along a half-plane up
to the dislocation line, shifted along L by the amount b and reattached.
Around the intersection of a screw dislocation with a surface, the epitaxial growth occurs, typically
in the form of a growth spiral that images the lattice planes around the defect.
4.3.1.3 60
◦ Dislocations
The most important dislocations in the zincblende lattice (Fig. 4.17) have the line vector along 110
With the Burger’s vector a/2 110 three different types of dislocations can be formed: edge, screw
and 60
◦ dislocations. The vicinity of the core of the latter is shown in more detail in Fig. 4.17d. We note
that the atomistic structure of 60
◦ dislocations is different for L along [110] and [−1 10]; depending
on whether the cations or anions are in the core, they are labeled α or β dislocations.