固体物理学课件：第三章晶体的缺陷及运动

2 Color of crystal
3 F center in ionic crystal
4 defects and mechanical properties , dislocation and deformation
、
F = U − TS
n,
∂F ∂n T
=0
u1
∆U = n1u1
∆F = ∆U − T∆S
S = kB lnW
W
N n1
∆F
=
∆U
− T∆S
=
n1u1
−
kBT
ln
(N + n1 )! N!n1!
N>>n1 X
ln x!= x(ln x −1)
n1
=
N
exp(−
u1 kBT
)
n2
=
N
exp(−
u2 kBT
)
—
1 2 3
2
1 2 3
1P 2 τ =1/P 3 P1 4 τ1 =1/P1 5 P2 τ2
exercise
1
Na
Na
1eV ,
Schottky
2
n E
Schottky N
n = N exp(− E ) 2k BT
What is a defect? Type of defects Why are defect important?
Si SF
Si etched pitch in large density Haze
2
(interstitial atom)
—
3
(impurity atom) interstitial , substitutional
Si、
。
、
(dislocation)
1
(edge dislocation)
2
(screw dislocation)
AFM SiC
1 (grain boundary)
E2 E2
exp(− E2 )
E2
kBT
P2
= ν 02
exp(−
E2 kBT
)
τ2
=
1 P2
=1
ν 02
exp(
E2 kBT
)
=
τ
02
exp(
E2 kBT
)
E1
P1
= ν 01
exp(−
E1 kBT
)
τ1
=
1 P1
=1
ν 01
exp( E1 ) kBT
=
τ
01
exp(
E1 kBT
)
P
n1
=
N
Point defects or Intrinsic
Linear defects Extrinsic
Volumeric defects
Why are defect important?
Defects are present in all crystals. Defect, even in small concentration, can have a dramatic impact on the properties of a materials. It is defects that make materials much more interesting. Without defect solid state electronic devices can not exist.
(inclusion)
1 surface method
:布
• •
Example: etch pits on the surface of a single crystal of tungsten
A row of etch pits formed at boundary between two germanium crystals
Si processing
What is a defect? • a imperfect or ‘mistake’ in the regular periodic
•Location of atoms, type of atoms
•Type and number of defects depends on the materials, its enviroment and the conditions under which it is processed type of defects
τ 01
kBT
exp(−
u1 kBT
)
n1 N-n1
n1《 N
NP *
1
n1 ≈ n1 N − n1 N
N n1
τ
2
n1
P
=
n1n2
N 2τ 2
=
n2 1
n1
NτBiblioteka Baidu2
NP
exp(− u1
= +
Nτ 2
n2 u2
n1
Nτ
)
2
τ2
kBT
P = 1 exp(− u1 + u2 + E2 )
τ 02
kBT
P = 1 exp(− u1 + u2 + E2 )
small angle boundary <10o
twin boundary
2
(stacking fault)
ABCABCABCABC ….. FCC —ABCABABCAB
AB AB AB AB … HCP 3 phase boundary
4 magnetic domain
SF
(precipitates) (voids, agglomerates of vancancies)
Defects affect microstructures and properties of materials Processing controls the presence and concentration of defects
0 1 2 3 dimensional defects (point defects, PD), 1 (vacancy) schottkey defects
2 KCl + 0.2% AgNO3
3x
X example :si dislocation
Si wafer
Haze milky area
Dislocation isolated bright point
4
AFM Si <111>
5 1 impurity doping in semiconductor