Martienssen W., Warlimont H. (Eds.). Handbook of Condensed Matter and Materials Data
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982 Part 5 Special Structures
B C
O, 2
A
1
Y
[001]
[010]Θ = 90°
X
Θ
3
–2 2 0
0–22
–1 –1 1
–2 0 0
–1 –1 –1
Relative to cubic axes Relative to OXYZ
Atom
Coordinates
Atomic positions
A
B
1
2
2
2
00
–
2
0
0
00
2
6
6
4
6
2
6
–1
3
–2
3
–3
3
002
1–1–1
–1 –1 1
–2 –2 0
Relative to cubic axes Relative to OXYZ
Atom
Coordinates
Atomic positions
A
B
1
2
2
–
2
–2
2
200
–1 0
10
00
Relative to cubic axes Relative to OXYZ
Atom
Coordinates
Atomic positions
A
B
1
2
0
0
–1
–2
2
0
1
0
0
2
1
0
2
0
1
0
0
2
1
0
0
0
–1
–2
bcc (100)
bcc (110)
bcc (111)
B C
O, 2
A
Θ = 125.26°
Y
[0
-
11]
X
[001]
Θ
1
Θ
B C
A
O, 3
1
2
Y
[
-
1
-
12]
X
[
-
110]Θ = 120°
b)
Fig. 5.2-2b Surface diagrams: body-centered cubic (bcc) positions given in terms of a/2 [2.2]
Part 5 2.1
The Physics of Solid Surfaces 2.1 The Structure of Ideal Surfaces 983
X
[01
-
1]
X
[01
-
1]
X
[01
-
1]
X
[01
-
1]
X X
Relative to
cubic axes
Relative to
OXYZ
Coordinates
Atomic positions
Atom
A
B
1'
2
3'
4
0
0
0
00 0 0
0
0
00
0
0
2
2
–1 1
11
2
1
–2
3
2
–
1
2
1
2
1
2
3
2
1
2
–
1
2
1
2
2
2
2
2
2
2
2
1
2
–
–1
Diamond and GaAs (
-
100) 0 δ 1/4; 1/2 δ 3/4
Diamond and GaAs (100) 1/4 δ 1/2; 3/4 δ 1
Relative to
cubic axes
Relative to
O'XYZ
Coordinates
Atomic positions
Atom
A'
B'
1
2'
3
4'
0
00
00
0
0
0
0000
0
1
11
–1
–1
–2 –2
1
2
–
3
2
–
1
2
1
1
2
1
2
1
2
–
2
2
2
2
2
2
2
2
2
2
1
2
–
–1
–3
2
Diamond and GaAs (100) 0 δ 1/4; 1/2 δ 3/4
Relative to
cubic axes
Relative to
OXYZ
Coordinates
Atomic positions
Atom
A
B
1'
2
3'
4
01–1
2
00
011 0 0
2
01–1
–2 0 0 0
0
0–2
–1
2
2
1
2
–
1
2
1
2
–
–3
2
1
2
1
2
2
2
2
2
2
2
–3
2
1
2
–
0
B C
O, 4
2
Y
[011]
Θ = 90°
A
Θ
Diamond
1'
3'
[0
-
11]
B C
O, 4
2
Y
[011]
A
Θ
GaAs
1'
3'
[0
-
11]
B' C'
O', 4'
2'
Y
[011]
A'
Θ
GaAs
1
3
B'
C'
O', 4'
2'
Y
[011]
Θ = 90°
A'
Θ
Diamond
1
3
B C
O, 4
2
Y
[011]
Θ = 90°
A
Θ
Diamond
3'
1'
B C
O, 4
2
Y
[011]
A
Θ
GaAs
3'
1'
c)
Fig. 5.2-2c Surface diagrams: diamond, GaAs (positions given in terms of a/2) Ga atoms are denoted by unprimed
symbols; As atoms by primed symbols and shaded cir cles [2.2]
Part 5 2.1
984 Part 5 Special Structures
Relative to
cubic axes
Relative to
OXYZ
Coordinates
Atomic positions
Atom
A'
B'
1
2'
3
4'
0
0
00 0 0 –22
–1 1
2
00
11 0 0
2
0
101
1
2
1
2
–
1
2
3
2
1
2
1
2
2
2
2
2
0
2
2
2
2
–1
–3
2
–1
2
X
B
C
O, 2
Y
[001]
A
Θ
GaAs
1'
1
[
-
110]
0'.2'
X
B
C
O, 2
Y
[001]
Θ = 90°
A
Θ
Diamond
1'
1
[
-
110]
0'.2'
X
X
Diamond and GaAs (111) 0 δ 3/4
Relative to
cubic axes
Relative to
OXYZ
Coordinates
Atomic positions
Atom
A
B
1'
4
5'
8
9'
–1 1 0 0 0
2
0
00
0
00
–1 1
–1 –1
–2 –1 –1
0
–
2
2
3
6
2
6
2
6
1
6
1
6
2
2
2
2
1
2
3
–
–2
3
5
2
3
–
–4
3
9
2
3
–
1
2
–
1
2
–
1
2
1
2
–
1
2
–
3
2
–
3
2
–
3
2
–
3
2
–
Θ
BC
A
GaAs
X
[
-
110]
Y
[
-
1
-
12]
1' 4
5' 8
Θ
BC
1'
O, 9', 12
A
Diamond
X
[
-
110]
Y
[
-
1
-
12]
Θ = 120°
4
5' 8
Diamond and GaAs (110)
Relative to
cubic axes
Relative to
OXYZ
Coordinates
Atomic positions
Atom
2
B
A
0'
1'
1
2
2'
–1 1 0 0 0
002 0 2 0
01 1
0
000
1
2
–
1
2
3
2
–1
1
2
–
1
2
–
1
2
–1 –1
3
2
–
1
2
–
3
2
2
2
3
2
0
2
2
2
2
3
2
1
2
–
2
2
–
2
2
–
2
–
2
Diamond and GaAs (
-
100) 1/4 δ 1/2; 3/4 δ 1
B'
C'
O', 4'
2'
Y
[011]
A'
Θ
GaAs
3
1
[0
-
11]
B'
C'
O', 4'
2'
Y
[011]
Θ = 90°
A'
Θ
Diamond
3
1
[0
-
11]
c) (cont.)
O, 9', 12
Fig. 5.2-2c cont.
Part 5 2.1
The Physics of Solid Surfaces 2.1 The Structure of Ideal Surfaces 985
Θ Θ
Θ Θ
Θ Θ
Relative to
cubic axes
Relative to
O'XYZ
Coordinates
Atomic positions
Atom
A'
B'
3
4'
7
8'
11
–1 1 0 0 0
0–11 0
00
00
0
–1 –1
–1 –1–2
2
5
2
–
3
2
–
3
2
–
3
2
–
3
2
–
1
2
–
1
2
–
1
2
–
1
2
–
–
2
2
2
2
2
2
3
6
1
6
1
6
2
6
2
6
3
2
3
–
2
3
–
7
2
3
–
–4
3
11
2
3
–
Relative to
cubic axes
Relative to
OXYZ
Coordinates
Atomic positions
Atom
Relative to
cubic axes
Relative to
O'XYZ
Coordinates
Atomic positions
Atom
A' 1–10 0 0
2
0
5
2
3
–
9
2
3
–
0
0
00
–1
0
B'
1
4'
5
8'
9
11
1
–
2
2
3
6
2
2
2
2
1
6
1
6
2
6
2
6
2
3
–
4
3
–
1
2
3
–
1
2
3
2
1
2
1
2
1
2
–
1
2
0
11
3
2
3
2
3
2
2
Diamond and GaAs (
-
1
-
1
-
1) 0 δ 1/4
BC
8.11'
4.7'
A
Diamond
X
[1
-
10]
Y
[
-
1
-
12]
Θ = 120°
BC
8.11'
4.7'
A
GaAs
X
[1
-
10]
Y
[
-
1
-
12]
Diamond and GaAs (111) 3/4 δ 1
B' C'
4'
O', 3, 12'
A'
Diamond
X
[
-
110]
Y
[
-
1
-
12]
Θ = 120°
7
8' 11
B' C'
A'
GaAs
X
[
-
110]
[
-
1
-
12]
4' 7
8' 11
Diamond and GaAs (
-
1
-
1
-
1) 1/4 δ 1
B' C'
5.8'
1.4'
A'
Diamond
X
[1
-
10]
Y
[
-
1
-
12]
Θ = 120°
B' C'
5.8'
1.4'
A'
GaAs
X
[1
-
10]
Y
[
-
1
-
12]
A
B
3'
4
7'
8
11'
1
–1
1
1
–1 0
01
01
12
00
0
00
0
0
2
1
2
1
2
1
2
1
2
3
2
3
2
3
2
3
2
5
2
1
6
1
6
2
6
2
6
3
6
–2
2
3
2
3
–
–2
3
7
2
3
–
–4
3
11
2
3
–
2
2
2
2
c) (cont.)
O', 3, 12'
O, 3', 12' O, 3', 12'
O', 9, 12' O', 9, 12'
Fig. 5.2-2c
cont.
Part 5 2.1
986 Part 5 Special Structures
5.2.1.2 Crystallographic Formulas
Some useful crystallographic formulas are listed in Table 5.2-1.
Table 5.2-1 Some useful crystallographic formulas
Cubic system Hexagonal system
Lattice parameter(s) aa, c
Plane (hkl) [hkil]
Plane normal, n [hkl][hkil/λ
2
]
λ =
√
2/3 c/a
Cosine of the angle
between planes with
normals n
1
, n
2
h
1
h
2
+k
1
k
2
+l
1
l
2
(h
2
1
+k
2
1
+l
2
1
)
1/2
(h
2
2
+k
2
2
+l
2
2
)
1/2
h
1
h
2
+k
1
k
2
+i
1
i
2
+l
1
l
2
/λ
2
(h
2
1
+k
2
1
+i
2
1
+l
2
1
/λ
2
)
1/2
(h
2
2
+k
2
2
+i
2
2
+l
2
2
/λ
2
)
1/2
Interlayer distance
fcc bcc
(c/λ)(h
2
+k
2
+i
2
+l
2
/λ
2
)
−1/2
(a/Q)(h
2
+k
2
+l
2
)
−1/2
(a/Q)(h
2
+k
2
+l
2
)
−1/2
Q = 1, except that Q = 2if Q =1, except that Q = 2if
at least one of hkl is even h +k +l is odd
Volume of the
primitive cell
1
4
a
3
1
2
a
3
1
2
a
2
c
√
3
Area of the surface
primitive cell
1
4
a
2
Q(h
2
+k
2
+l
2
)
1/2
1
2
a
2
Q(h
2
+k
2
+l
2
)
1/2
ac[(h
2
+k
2
+i
2
+l
2
/λ
2
)/2]
1/2
5.2.2 Surface Reconstruction and Relaxation
The structure of a real (clean) surface may differ from
that of an ideally truncated crystal. Two types of devia-
tion are possible: relaxation and reconstruction.
Relaxation consists of a rigid inward or outward
displacement of the uppermost planes of the surface,
the symmetry in the surface plane being maintained. In
contrast, in the caseof reconstruction, the displacements,
of atoms alter the 2-D symmetry of the surface.
5.2.2.1 Definitions and Notation
If a and b are the basis vectors of an ideally terminated
surface and A and B those of the reconstructed surface,
then
A = m
11
a +m
12
b ,
B = m
21
a +m
22
b .
The matrix
m
11
m
12
m
21
m
22
characterizes the reconstruction. If all the m
ij
are inte-
gers the reconstruction is said to be commensurate. If
at least one of the m
ij
is irrational, the reconstruction
is said to be incommensurate. The term “incommensu-
rate”, however, is often extended to rational noninteger
numbers. For example the reconstruction of Mo(100),
20
02
,
is called incommensurate.
If the angle between A and B is the same as that
between a and b, a simpler notation introduced by
Wood [2.17] can be used, namely:
p(u × v)RΦ or c(u × v)RΦ,
where u = A/a, v = B/b; p and c stand for primitive and
centered, respectively, and RΦ means a rotation of Φ of
the cell (A,B) with respect to (a, b). When Φ = 0, RΦ
is omitted. Also, the prefix p and the rotation symbol R
are often omitted.
Figure 5.2-3 shows a few examples of reconstruction
for a layer of adatoms on top of a substrate. The matrix
and Wood notations are compared. It can be seen from
the figure that (i) the elementary cell is not uniquely
Part 5 2.2
The Physics of Solid Surfaces 2.2 Surface Reconstruction and Relaxation 987
a)
Matrix
notation
Wood
notation
20
01
2 × 1
11
1–1
( 2 × 2)
11
1–1
c(2 × 2)
b)
c)
d)
10
01
1 × 1
Fig. 5.2-3a–d Examples of reconstruction for a layer of
adatoms (small shaded circles) on top of a square lattice
substrate (large empty circles). Matrix and Wood notations
are compared. Notice that
(c) and (d) differ only for the
choice of the unit cell
defined (as in 3-D), and (ii) the symmetry alone does
not define unequivocally the reconstruction. In practice
this means that LEED (low-energy electron diffraction)
patterns are not enough to define a model for a recon-
struction and that other techniques (including dynamical
LEED) are necessary.
The energies associated with reconstruction are
∼10
−2
eV/atom in metals and ∼10
−1
eV/atom in
semiconductors. Metals are therefore seldom re-
constructed, while semiconductors are very often
reconstructed.
A detailed discussion of the various problems
connected to relaxation and reconstruction are found
in [2.3–8]
Table 5.2-2 Reconstruction and relaxation of metals
1
Metal Structure Face Reconstruction Remarks
Ag fcc
(100) 1×1 Unrelaxed
(110) 1×1 Relaxed
(111) 1×1 Unrelaxed
Al fcc
(100) 1×1 Unrelaxed
(110) 1×1 Relaxed
(111) 1×1 Relaxed
5.2.2.2 Metals
Table 5.2-2 summarizes the essential features of re-
construction or relaxation at metal surfaces. Vertical
relaxations (in % of the bulk interlayer distances) are
given in Table 5.2-3.
Reconstruction Models
In Figs. 5.2-4 and 5.2-6, some accepted models of recon-
structed surfaces of metals are shown. Table 5.2-4 gives
the parameters for the 2 ×1 missing-row reconstruction
of Au(110), Ir(110), and Pt(110). The missing-row re-
construction stabilizes the surfaceby relieving the elastic
stress.
∆d
12
p
2
∆d
23
p
4
B
3
Fig. 5.2-4 Side view of the atomic positions in the 2× 1
missing-row reconstruction of the (110) face of Au, Ir, and
Pt, and definition of parameters used in Table 5.2-4
Au (111)
20Å
20Å
Fig. 5.2-5 STM image of the 23 × 1 reconstruction of
Au(111) [2.18]
Part 5 2.2
988 Part 5 Special Structures
Table 5.2-2 Reconstruction and relaxation of metals
1
, cont.
Metal Structure Face Reconstruction Remarks
Au fcc
(100) 5×20 T < 700 K. Reconstruction model: incommensurate hexagonal layer
6×6 700 < T < 820 K
(110) 1×2 Reconstruction model: missing-row (Fig. 5.2-4 and Table 5.2-4).
Reversible phase transition to 1 × 1 at T
∼
=
690 K
(111) 1×23 Reconstruction model: see Fig. 5.2-5 (observed by STM)
Co
hcp (0001) 1×1 Unrelaxed
cubic phase (100) 1×1 Relaxed
(111) 1×1 Unrelaxed
Cu fcc
(100) 1×1 Relaxed
(110) 1×1 Relaxed
(111) 1×1 Essentially unrelaxed
Fe bcc
(100) 1×1 Relaxed
(110) 1×1 Essentially unrelaxed
(111) 1×1 Relaxed
Ir fcc
(100) 1×5 T < 2000 K. Reconstruction model: hexagonal layer with buckling.
A metastable 1 × 1 phase is also observed
(110) 1×2 Reconstruction model: missing-row (Fig. 5.2-4 and Table 5.2-4).
A metastable 1× 1 phase is also observed
(111) 1×1 Essentially unrelaxed
Mo bcc
(100) 2.2×2.2 T < 300 K, incommensurate
1×1 T > 300 K, relaxed
(110) 1×1 Relaxed
Ni fcc
(100) 1×1 Relaxed (results controversial)
(110) 1×1 Relaxed
(111) 1×1 Unrelaxed
Pb fcc (110) 1×1 Relaxed; annealing at T > 340 K gives a c(2×4) reconstruction
Pd fcc
(100) 1×1 Essentially unrelaxed
(110) 1×1 Relaxed
(111) 1×1 Unrelaxed
Pt fcc
(100) 1×5 77 K < T < 1900 K. Reconstruction model: hexagonal layer slightly
rotated. Other metastable superstructures, 1 × 1 and 5 × 20, are observed
(110) 1×2 Reconstruction model: missing-row (Fig. 5.2-4 and Table 5.2-4).
Reversible transition to 1×1 at T = 1100 K
(111) 1×1 Essentially unrelaxed
Rh fcc
(100) 1×1 Essentially unrelaxed
(110) 1×1 Relaxed
(111) 1×1 Relaxed
Ta bcc (100) 1×1 Relaxed
Th fcc (111) 1×1 After annealing at T ≈ 1000 K becomes 9× 9
V bcc
(100) 1×1 Relaxed
(110) 1×1 Essentially unrelaxed
W bcc
(100) c(2 × 2) T < 400 K. Reconstruction model: see Fig. 5.2-6
1×1 T > 400 K. Relaxed
(110) 1×1 Unrelaxed
1
Reference to the original papers is given in [2.3]
Part 5 2.2
The Physics of Solid Surfaces 2.2 Surface Reconstruction and Relaxation 989
Table 5.2-3 Vertical relaxation of metals. Data are given as a percentage of the bulk interlayer distance d
bulk
. The data are average
values from various authors.
1
Errors are expressed as standard deviations from the average. The + sign corresponds to expansion.
LEIS, low-energy ion scattering; HEIS, high-energy ion scattering; MEIS: medium-energy ion scattering
Crystal Face d
bulk
(Å) d
12
(%) d
23
(%) d
34
(%) Technique
Ag
(110) 1.445 −7.5 (13) +1.6 (6) −2 (2) LEED
−8.6 (8) +5.1 (8)
2
− LEIS, MEIS
Al
(100) 2.025 0 (5) − − LEED
−2.4 (24) − − HEIS
(110) 1.427 −7 (2) +5.0 (2) −1.6 LEED
(111) 2.329 +1.5 (6) − − LEED
Cu
(100) 1.807 −1.1 +1.7 <1 LEED
−2.3 (2) − − MEIS
(110) 1.278 −8.3 (9) +2.3 −0.9 LEED
−7 (3) +2.9 (4) − LEIS, MEIS, HEIS
(111) 2.087 +0.8 (2) − − LEED
Fe
(100) 1.433 −1.4 (30) − − LEED
(110) 2.027 +0.5 (20) − − LEED
+1 (2) − − MEIS
(111) 0.827 −16.9 (30) −9.8 (30) +4.2 (36) LEED
−29 (7) +7 (5)
2
− MEIS
Ir (100) 1.920 +5.2 − − LEED
1× 1 metastable
Mo
(100) 1.574 −9 (2) +0.25 (175) +0.5 (30) LEED
(110) 2.225 −1.6 − − LEED
(111) 0.909 −18 +4 − LEED
−16 +4 − LEIS
Ni
(110) 1.245 −7 (2) +3.3 (3) −0.5 (7) LEED
−6.9 (21) +3.0 (6) − MEIS, HEIS
Pb
(110) 1.750 −17.6 (13) +3.8 (10) −5.9 (13) LEED
−15.8 +7.9 −6.8 MEIS
Pd (110) 1.375 −5.6 (4) +1.5 (10) − LEED
Rh
(100) 1.902 +0.5 (10) 0 (15) − LEED
(110) 1.345 −3.5 (25) − − LEED
(111) 2.196 −1 − − LEED
Ta
(100) 1.653 −11 +1 − LEED
−10.5 − − PED
V (100) 1.514 −6.8 (2) +1 − LEED
W
(100) 1.583 −6.2 (14) +1 − LEED
high-T phase −5.6 − − X-ray
1
References to the original papers and individual errors are given in [2.3–5]
2
Inconsistency between LEED and ion scattering data
Part 5 2.2
990 Part 5 Special Structures
Table 5.2-4 Structural parameters of the 1 ×2 reconstruction of the (110) face of Au, Ir, and Pt (average values from
variousauthors
1
). Errors are expressedas standard deviationsfrom the average.An illustration of the model and parameters
is given in Fig. 5.2-4. The bulk interlayer spacings are 1.445 Å for Au, 1.358 Å for Ir, and 1.387 Å for Pt
Crystal d
12
(Å) d
23
(Å) p
2
(Å) p
4
(Å) B
3
(Å) Technique
Au −0.25 (3) 0.03 0.07 − 0.24 LEED
−0.20 (4) 0.06 < 0.1 − 0.20 LEIS, MEIS
−0.32 − 0.05 0.05 − X-ray
Ir −0.17 −0.16 0.04 − 0.23 LEED
−0.13 − − − − MEIS
Pt −0.30 (5) −0.04 (10) 0.06 (2) 0.08 (3) 0.22 (7) LEED, RHEED
−0.22 (4) 0.06 (4) < 0.04 − 0.10 MEIS
−0.27 −0.11 0.05 0.04 − X-ray
1
References to the original papers and individual errors are given in [2.3]
1st layer
[110]
[001]
4th layer
a
a)
[110]
[001]
b)
b
A
B
c)
2nd layer
3rd layer
[110]
[010][1
–
00]
[1
–
10]
W(001)
m
m
a
b
g
g
g
(010)
(100)
Fig. 5.2-6 Top view of the c(2 × 2) reconstruction of
the W(001) face. g, glide plane; m, mirror plane.
Shaded circles, surface atoms; empty circles, second-layer
atoms [2.19]
5.2.2.3 Semiconductors
The essential features of reconstruction and relaxation
of semiconductor surfaces are given in Table 5.2-5,
together with indications of the methods of prepa-
ration and remarks on pecularities of the specific
surfaces.
Fig. 5.2-7a–c Dimer models for the 2× 1 reconstruction
of Si and Ge(100) faces, with
(a) symmetric and (b) buck-
led dimers (side views).
(c) Top view of the symmetric
case. Ideal (shaded) and reconstructed unit cells are
shown
Part 5 2.2
The Physics of Solid Surfaces 2.2 Surface Reconstruction and Relaxation 991
Reconstruction Models
In semiconductors, directional bonds are present that are
unsaturated at the surface. The driving force for recon-
struction is the tendency to minimize the number of such
dangling bonds (DBs).
Table 5.2-5 Reconstruction and relaxation of semiconductors. IBA, ion bombardment and annealing; MBE, molecular-beam
epitaxy; DAS, dimer–adatom–stacking fault. References are given in [2.3]
Crystal Face Reconstruction Preparation Model Remarks
symmetry
Diamond
(100) 2×1 Annealing Symmetric dimers
T > 1300 K
(110) 1×1 Annealing Truncated bulk
(111) 2×1 Annealing π-bonded chains
T > 1200 K
Si
(100) 2×1 IBA or MBE Symmetric and/or buckled
dimers (Fig. 5.2-7)
p(2 × 2) Same as above Ordered arrangement of Present locally (∼ 5%)
buckled dimers (Fig. 5.2-8)
c(4 × 2) Same as above Ordered arrangement of Present locally (∼ 5%)
buckled dimers (Fig. 5.2-10)
(110) 16 × 2 Annealing Dimers + adatoms + terraces (?) Other superstructures (probably
T > 1300 K stabilized by impurities) are
32× 2 Same as above Same as above observed: 4 × 5, 5 × 1, 2 × 1
(111) 2×1 Cleaving π-bonded chains Transforms irreversibly into 7×7
(Fig. 5.2-11, Table 5.2-6) at T 550 K
7×7 Cleaving + annealing at DAS + vacancies (Fig. 5.2-13) Equilibrium reconstruction
550 K or Annealing at
900 K or MBE
5×5 Same as above Same as above Present locally near steps
Ge
(100) 2×1 IBA or MBE Symmetric and/or buckled
dimers
p(2 × 2) Same as above Ordered arrangement of Present locally
buckled dimers
c(4 × 2) Same as above Same as above Same as above
(111) 2×1 Cleaving at π-bonded chains Transforms irreversibly into c(2×8)
40 < T < 400 K at T 400 K
c(2 × 8) Annealing Adatoms (Fig. 5.2-16) Equilibrium reconstruction
T > 400 K
GaAs
(100) c(2 × 8) IBA Ga (or As) dimers (?) As coverage 0.22–0.52
T 850 K
c(4 × 4) MBE + annealing As coverage 1–1.25
T 670 K
4×6 IBA As coverage 0.27–0.31
T 770–850 K
(110) 1×1 Cleaving, IBA Rotation/relaxation
(Fig. 5.2-17, Table 5.2-8)
(111)Ga 2×2 IBA or MBE Ga vacancies
(
¯
1
¯
1
¯
1)As 2×2 Same as above As trimers
GaP (110) 1×1 Cleaving, IBA Rotation/relaxation
(Fig. 5.2-17, Table 5.2-8)
GaSb (110) 1×1 Cleaving Same as above
In sp
3
-bonded crystals, the energy associated with
the angles between the bonds is rather small. In con-
trast, the energy associated with the length of the bonds
is large. Accordingly, reconstruction of covalent (or
moderately ionic) semiconductors occurs through dis-
Part 5 2.2