MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Transport in metallic systemsTransport in amorphous systemsTransport in semiconductors and heterojunctionsTransport in conjugated molecular systems
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Classical Theory of Electrical Conduction in Materials (Drude Model)--- charge carrier density
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Classical Theory of Electrical Conduction in Materials (Drude Model)--- charge carrier mobility
Nq
EENqvNqj
1
)(
densitycurrent
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
The history of electricity goes back more than two thousand years, to the time the Ancient Greeks discovered that rubbing fur on amber caused an attraction between the two. By the 17th century, many electricity-related discoveries had been made, such as the invention of an early electrostatic generator, the differentiation between positive and negative currents, and the classification of materials as conductors or insulators. In the year 1600, English physician William Gilbert conned the term electric, from the Greek elektron, to identify the force that certain substances exert when rubbed against each other. While many believe Benjamin Franklin to be the father of electricity, current findings seem to show otherwise. In 1752, Franklin is said to have performed the famous experiment of flying a kite during a thunderstorm, which led to the discovery that lightning and electricity were somehow related. Modern scientists know this to be something of a tall tale, since being hit by lightning would have been fatal. It's likely that Franklin was actually insulated, away from the path of lightning. The kite experiment helped Franklin establish a relationship between lightning and electricity, which led to the invention of the lightning rod. Benjamin Franklin went on to observe other phenomena related to electricity, but many believe that he didn't actually discover its true nature. In 1800, Italian-born physicist Alessandro Volta constructed the voltaic pile, later known as the electric battery, the first device to produce a steady electric current. It was Volta, not Franklin, who discovered that certain chemical reactions could produce electricity. Volta also created the first transmission of electricity by linking positively-charged and negatively-charged connectors and driving an electrical charge, or voltage, through them. It wasn't until 1831 that electricity became viable for use in technology. English scientist Michael Faraday created the electric dynamo, a crude precursor of modern power generators. This invention opened the door to the new era of electricity. A few decades later, in 1879, Thomas Alva Edison invented the light bulb. Source:www.wisegeek.com
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Classical Theory of Electrical Conduction in Materials (Drude Model)--- temperature effect
a
u
Electron
S = a2
=u
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
n
T
T
0
0
Fig. 2.6: The resistivity of various metals as a function of temperatureabove 0 °C. Tin melts at 505 K whereas nickel and iron go through amagnetic to non-magnetic (Curie) transformations at about 627 K and
1043 K respectively. The theoretical behavior (~ T) is shown forreference.[Data selectively extracted from various sources including sections inMetals Handbook, 10th Edition, Volumes 2 and 3 (ASM, MetalsPark, Ohio, 1991)]
T
Tungsten
Silver
Copper
Iron
Nickel
Platinum
NiCr Heating Wire
Tin
Monel-400
Inconel-825
10
100
1000
2000
100 1000 10000
Temperature (K)R
esis
tivi
ty (
n
m)
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
http://Materials.Usask.Ca
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
120 V
40 W
0.333 A
Fig. 2.9: Power radiated from a light bulb at 2408 °C is
equal to the electrical power dissipated in the filament.
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Classical Theory of Electrical Conduction in Materials --- impurity effects
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Matthiesen’s rule
Temperature (K)
0
20
40
60
0 100 200 300
T
I
CW
100%Cu (Annealed)100%Cu (Deformed)
Cu-1.12%Ni
Cu-1.12%Ni (Deformed)
Cu-2.16%Ni
Cu-3.32%Ni
Fig. 2.8: Typical temperature dependence of the resistivity ofannealed and cold worked (deformed) copper containing variousamount of Ni in atomic percentage (data adapted from J.O. Linde,Ann. Pkysik, 5, 219 (1932)).
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
http://Materials.Usask.Ca
Resis
tivit
y (
n
m)
defimpth
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Linde’s rule of metal’s resistivity
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
mass. atomic M,density; , constant; Avogadro ,N0
0
M
NNN a
Nq
EENqvNqj
1
)(
densitycurrent
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Quantum Mechanical Consideration
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Quantum Mechanical Consideration
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
10610310010-310-610-910-1210-1510-18 109
Semiconductors Conductors
1012
Conductivity (m)-1
AgGraphite NiCrTeIntrinsic Si
Degenerately
Doped Si
Insulators
Diamond
SiO2
Superconductors
PETPVDF
Amorphous
As2Se
3
Mica
Alumina
Borosilicate Pure SnO2
Inorganic Glasses
Alloys
Intrinsic GaAs
Soda silica glass
Many ceramics
Metals
Polypropylene
Figure 2.24: Range of conductivites exhibited by various materials
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
http://Materials.Usask.Ca
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Transport in metallic systemsTransport in amorphous systemsTransport in semiconductors and heterojunctionsTransport in conjugated molecular systems
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Anderson Localization Theory (PW Anderson, Phys. Rev. 109, 1492 (1958)
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Conduction through hopping
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Conduction through hopping
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Modified hopping conduction by Efros and Shklovskii
T
T
c
c
e
ΔE
P
E
eR
ΔEΔE
ΔE
ReΔE
0
0
2
2
0
energy hopping optimum find to
4
0
transporthoppingfor requiredenergy The
4/
behindleft “holes” its andelectron hopping a
betweenenergy n interactio Coulomb The
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Transport in metallic systemsTransport in amorphous systemsTransport in semiconductors and heterojunctionsTransport in conjugated molecular systems
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Conduction in semiconductors vs metals
Fig. 5.20: Temperature dependence of electrical conductivityfor a doped (n-type) semiconductor.
log(n)
Intrinsic
Extrinsic
Ionization
log()
log()
T 3/2 T 3/2
Lattice
scattering
Impurity
scattering
1/TLow TemperatureHigh Temperature
T
Metal
Semiconductor
Logari
thm
ic S
cale
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
http://Materials.Usask.Ca
Resi
stiv
ity
hhee eNeN
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Conduction through tunneling
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Conduction through tunneling
L
R
L
R
L
dEETh
eI
dEETEfEfh
eIII
dEETEfh
eI
dEETEfh
eI
URLRL
URR
ULL
)(2
function. step ~ is function Fermiature,low temperAt
)()),(),((2
currentnet The
)(),(2
left right to from tunnelingelectronby causedcurrent The
)(),(2
right left to from tunnelingelectronby causedcurrent The
?
MSE462 (Prof. Z.H. Lu) : Charge Transport PhenomenaConduction through tunneling----P-N Junction Esaki Diode
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Conduction through tunneling
----P-N Junction Esaki Diode
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Quantum tunneling semiconductor devicesRTD
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Quantum tunneling semiconductor devicesRTD
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Quantum tunneling semiconductor devices-RTD (S.M. Sze, Modern Semiconductor Device Physics)
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Transport in metallic systemsTransport in amorphous systemsTransport in semiconductors and heterojunctionsTransport in conjugated molecular systems
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
Cathode
Anode
Substrate
Al
q
Photo source: Samsung
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
WHY and How Molecule Conduct Charge?
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
WHY and How Molecule Conduct Charge?
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena
WHY and How Molecule Conduct Charge?Injection and Transport
Transporting molecule
Hopping conduction
electric field
MSE462 (Prof. Z.H. Lu) : Charge Transport Phenomena