Transcript Sinai University Faculty of Engineering Science Department

Sinai University Faculty of Engineering Science
Department of Basic science
From Principles of Electronic
Materials and Devices, Third
Edition, S.O. Kasap (©
1
Course name: Electrical materials
Code: ELE163
Text references
1- Principles of Electronic Materials and Devices, 3rd edition
2- Kittel, Introduction to Solid State Physics
3-College Physics , Serway, 7th edition
4-Lecture notes (power points)
5- Internet sites
Prepared by
Pr Ahmed Mohamed El-lawindy
[email protected]
Faculty site: www.engineering.su.edu.eg
From Principles of Electronic
Materials and Devices, Third
Edition, S.O. Kasap (©
2
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instructors if the 3rd Edition
has been adopted for his/her
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individuals who have
purchased a copy of the third
edition with CD-ROM
Electronic Materials and
Devices to use these slides in
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provided that the book title,
author and © McGraw-Hill are
displayed under each diagram.
From Principles of Electronic
Materials and Devices, Third
Edition, S.O. Kasap (©
Ch 3
Elementary Quantum Physics
Introduction:
Modern Physics: At the end of 1900 and beginning of 2000 century
Quantum mechanics
Theory of relativity
• It can explain the electrical conductivity,
The mean speed of electrons are independent of temperature.
• Thermal radiation emitted by a black-body,
• The modern definition of voltage and ohm are based on Josephson and quantum
hall effect, both of which are quantum mechanical phenomena.
Important discovery
•
•
Wave-particle duality, light can be treated as photons which has no mass but
momentum, h/l, and interact directly with electrons, like a particle.
Also particles, electrons, can be treated as waves which scatter, diffract interfere, and
etc….
From Principles of Electronic
Materials and Devices, Third
Edition, S.O. Kasap (©
3.1 Photons
3.1.1 Light as a wave
Interference, diffraction, refraction, reflection are explained by the wave theory
The classical view of light as an electromagnetic wave.
An electromagnetic wave is a traveling wave with time-varying electric and magnetic
fields that are perpendicular to each other and to the direction of propagation.
Fig 3.1
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Light as a wave
Traveling wave description
E y ( x, t )  Eo sin(kx  t )
Intensity of light wave
Is the energy flowing per unit per unit time
k 
c 

2
l
 
k
 2v
vl
1
2
I  c oE o
2
 is the angular velocity,
c speed of light
k is the wave number
l is the wave length
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Young`s Double slit interference
S1 P  S 2 P  nλ
n  1, 2, 3, ... constructive interference
1
S1 P  S 2 P  (n  )λ
2
n  1, 2, 3,
Fig 3.2
destructive nterference
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
X-ray diffraction
Diffraction patterns obtained by passing X-rays through crystals can only be
explained by using ideas based on the interference of waves. (a) Diffraction of Xrays from a single crystal gives a diffraction pattern of bright spots on a
photographic film. (b) Diffraction of X-rays from a powdered crystalline material
or a polycrystalline material gives a diffraction pattern of bright rings on a
photographic film.
Fig 3.3
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
(c) X-ray diffraction involves constructive interference of waves being
"reflected" by various atomic planes in the crystal.
Fig 3.3
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Bragg’s Law
Bragg diffraction condition
2d sinθ  nλ n  1, 2, 3, ...
The equation is referred to as Bragg’s law, and arises from the
constructive interference of scattered waves.
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Waves as particles
• Light can behave like particles of zero rest mass.
• This is the only way to explain a vast number of
experiments, Photoelectric and Compton effects.
• One can view light as a stream of discrete entities or energy
packets called photons.
• Each photon carry a quantum of energy hn and momentum
h/l, where h is Plank`s constant, l is the wavelength, and n
is the light frequency.
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
3.1.2 The photoelectric effect.
Fig 3.4
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
eV0= ½ mev2=KEm
(a) Photoelectric current vs. voltage when
the cathode is illuminated with light of
identical wavelength but different
intensities (I). The saturation current is
proportional to the light intensity
(b) The stopping voltage and therefore
the maximum kinetic energy of the
emitted electron increases with the
frequency of light u. (Note: The light
intensity is not the same)
Results from the photoelectric experiment.
Fig 3.5
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
The effect of varying the frequency of light and the cathode material in the photoelectric
experiment. The lines for the different materials have the same slope h but different intercepts
Fig 3.6
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Photoelectric Effect
Photoemitted electron’s maximum KE is KEm
KEm  hu  hu0
Work function, F0
The constant h is called Planck’s constant.
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
The PE of an electron inside the metal is lower than outside by an energy called the
workfunction of the metal. Work must be done to remove the electron from the metal.
Fig 3.7
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Intuitive visualization of light consisting of a stream of photons (not to be taken
too literally).
SOURCE: R. Serway, C. J. Moses, and C. A. Moyer, Modern Physics, Saunders College
Publishing, 1989, p. 56, figure 2.16 (b).
Fig 3.8
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Light Intensity (Irradiance)
Classical light intensity
1
2
I  c oE o
2
In the photonic interpretation of light, Light
Intensity
I  ph hu
Photon flux
ph 
N ph
At
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Light consists of photons
From Principles of Electronic
Materials and Devices, Third
Edition, S.O. Kasap (©
X-rays are photons
X-ray image of an American one-cent coin captured using an x-ray a-Se HARP camera.
The first image at the top left is obtained under extremely low exposure and the
subsequent images are obtained with increasing exposure of approximately one order of
magnitude between each image. The slight attenuation of the X-ray photons by Lincoln
provides the image. The image sequence clearly shows the discrete nature of x-rays, and
hence their description in terms of photons.
SOURCE: Courtesy of Dylan Hunt and John Rowlands, Sunnybrook Hospital, University of
From Principles of Electronic
Toronto.
Materials and Devices, Third
Edition, S.O. Kasap (©
3.1.3 Compton effect
KE= hn-hn`
P=h/l
2n
Ehn(h/2) 
Scattering of an X-ray photon by a
“free” electron in a conductor.
Fig 3.9
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
The Compton experiment and its results
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
3.1.4 Black body radiation
Experimental observation
A- All objects emit and absorb energy in the form of radiation
B- The energy of such radiation, thermal radiation, depends on the radiation wavelength and
temperature.
Object in thermal equilibrium with its surrounding, i.e. both has the same
temperature:
Absorb as much energy as it emits
If the temperature of the object above the temperature of its surrounding, there is a
net emission of radiation energy
The maximum amount of energy emitted by an object is called black
radiation
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
body
3.1.4 Black body radiation
Il is the spectral irradiance:
the emitted radiation energy (power per unit
area) per unit wavelength
Ildl is the intensity in a small range of wavelength
Spectral irradiance vs. wavelength at
two temperatures
(3000K is about the temperature of the
incandescent tungsten filament in a light
bulb.)
We assume that the characteristics of the radiation emerging from the aperture represent
those of the radiation within the cavity
Fig 3.11
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Classical physics
Classical physics predicts that the acceleration and deceleration of the charges due to various
thermal vibration, oscillation, or motion of atoms in the surface region of the cavity material
results in electromagnetic waves, which interfere with each other producing standing waves
with different wavelengths, of energy kT.
Ilα 1/l4 and Ilα T
Fig 3.11
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Black Body Radiation
Plank showed that the experimental data can be explained if we assume that the
radiation within the cavity involves the emission and absorption of discrete amount of
energy by the oscillation of the molecules of the cavity
Planck’s radiation law
2hc2
Il 
 hc  
5
l exp
  1
 lkT  


Stefan’s black body radiation law
Stefan’s constant
 2 5 k 4  4
T
Ps   I l dl  
2 3 
 15c h 
0
PS   S T 4
2 5 k 4
 S  2 3  5.670108 W m 2 K 4
15cof Electronic
h Materials and
From Principles
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Wien`s displacement law
lmax T~ 2.89x10-3 mK
Fig 3.11
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Assignment
• Draw the equation at different temperature,
3000K and 2500 K at different wavelengths, from
0 mm to 5 mm in steps of 0.1 mm.
2hc2
Il 
 hc  
5
l exp
  1
  lkT  
• Please E-mail your result to
• [email protected]
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Example 3.4 Stefan’s law for real surfaces
Electromagnetic radiation emitted from a hot surface
Pradiation = total radiation power emitted (W = J s-1)
Pradiation  S S [T  T ]
4
S = Stefan’s constant, W m-2 K-4
 = emissivity of the surface
 = 1 for a perfect black body
 < 1 for other surfaces
S = surface area of emitter (m2)
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
4
0
3.2 The electron as a wave
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Young’s double-slit experiment with electrons involves an electron gun and two slits in a
Cathode ray tube (CRT) (hence, in vacuum).
Electrons from the filament are accelerated by a 50 kV anode voltage to produce a beam that
is made to pass through the slits. The electrons then produce a visible pattern when they strike
a fluorescent screen (e.g., a TV screen), and the resulting visual pattern is photographed.
SOURCE: Pattern from C. Jonsson, D. Brandt, and S. Hirschi, Am. J. Physics, 42, 1974, p.9,
figure 8. Used with permission.
Fig 3.12
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Fig 3.13
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
Fig 3.13
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
The diffraction of electrons by crystals gives typical diffraction patterns that would be
Expected if waves being diffracted as in x-ray diffraction with crystals [(c) and (d) from
A. P. French and F. Taylor, An Introduction to Quantum Mechanics (Norton, New York,
1978), p. 75; (e) from R. B. Leighton, Principles of Modern Physics, McGraw-Hill, 1959),
p. 84.
Fig 3.13
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)
3.2.1 De Broglie Relationship
Wavelength l of the electron depends on its momentum p
De Broglie relations
Examples
h
l
p
OR
p
h
l
1- A 50 g golf ball at a velocity of 20 m/s
h h
6.63x1034 Js
34
l  -1


6
,
63
x
10
m
3
1
2- A proton travelling at 2200 ms
l=
0.18
nm
p mv (50x10 kg)(20ms )
3- Electron accelerated by 100 V
l= 0.123 nm
From Principles of Electronic Materials and
Devices, Third Edition, S.O. Kasap (©
McGraw-Hill, 2005)