Figure 16.31: Two-dimensional representations of (a) a quartz crystal and (b) a quartz glass.

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Figure 16.31: Two
-
dimensional representations of
(a) a quartz crystal and (b) a quartz glass.

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Figure 16.28: The p orbitals (a) perpendicular to the plane of

th carbon ring system in graphite can combine to form

(b) an extensive pie bonding network.

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The Electronic Configuration of a Magnesium Atom

n

l

m
l

m
s

3

0

0

+1/2

3

0

0

-
1/2

Mg: (Ne)3s
2






1s

2s

3s

2p

3p

Empty 3p
orbitals in Mg
valence shell

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Orbital energy
levels

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Figure 16.24: A representation of the energy
levels (bands) in a magnesium crystal

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Figure 16.27: Partial representation of the MO
energies in (a) diamond and (b) a typical metal

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Electron sea model for
metals

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Bonding in Solids

Metallic Solids

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Band structure of Semiconductors

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Band Diagram
:
Semiconductor with No Doping


At T = 0
, lower
valence band is filled

with electrons and upper
conduction band is empty
, leading to zero conductivity.


Fermi energy

E
F

is at midpoint of small energy gap (<1

eV)
between conduction and valence bands.



At T > 0
, electrons thermally “excited” from valence to conduction
band, leading to measurable conductivity.

E
F

E
C

E
V

Conduction band

(Partially Filled)

Valence band

(Partially Empty)

T > 0

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Silicon Crystal
Doped with (a)
Arsenic and (b)
Boron


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Figure 16.33: Energy
-
level diagrams for (a) an

n
-
type semiconductor and (b) a p
-
type semiconductor.

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pn junction

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Figure 16.34: The p
-
n junction involves the

contact of a p
-
type and an n
-
type semiconductor.

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PN Junction
-

7

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PN Junction with Applied Potential

No current, Barrier Larger

Current Flows, Barrier Smaller

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Herbert Kroemer

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L
ight
A
mplification by
S
timulated
E
mission
R
adiation

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Solar Cells

n
-
type

p
-
type

Photons

Electron

Hole

Load

p
-
n

Junction under Illumination

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Solar Panels


Photovoltaic Cells

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Schematic of a Photovoltaic (solar) cell

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A schematic of two circuits

connected by a transistor.

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Photolithography to make semiconductor

integrated circuits

http://britneyspears.ac/physics/fabrication/photolithography.htm

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(a)
-
(h) The steps for forming a transistor in a
crystal of initially pure silicon.

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(a)
-
(h) The steps for forming a transistor in a
crystal of initially pure silicon.
(cont’d)

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Semiconductors


key points to remember



Band structure:


Valence band


gap


conduction band



DOPING:


Group V


n type
,


Group III


p type



n
-
p junctions



Devices:


(LED, laser, transistor, solar cell)


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Figure 16.24: A representation of the energy
levels (bands) in a magnesium crystal

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Band structure of Semiconductors

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Semiconductors


key points to remember



Band structure:


Valence band


gap


conduction band



DOPING:


Group V


n type
,


Group III


p type



n
-
p junctions



Devices:


(LED, laser, transistor, solar cell)


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31


Silicon Crystal
Doped with (a)
Arsenic and (b)
Boron


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Semiconductors


key points to remember



Band structure:


Valence band


gap


conduction band



DOPING:


Group V


n type
,


Group III


p type



n
-
p junctions



Devices:


(LED, laser, transistor, solar cell)


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pn junction

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Semiconductors


key points to remember



Band structure:


Valence band


gap


conduction band



DOPING:


Group V


n type
,


Group III


p type



n
-
p junctions



Devices:


(LED, laser, transistor, solar cell)


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C
60

crystals

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Ionic liquids