The document summarizes the key differences between insulators and semiconductors that influence their conductivity. Insulators have a large band gap between the valence and conduction bands, making it difficult for electrons to gain enough energy to conduct electricity. Semiconductors have a smaller band gap, allowing electrons to reach the conduction band at ordinary temperatures and conduct. Doping semiconductors with impurities increases the number of charge carriers and decreases scattering, improving mobility and conductivity.
Describes electrostatic principles and concepts.
**More good stuff available at:
www.wsautter.com
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http://www.youtube.com/results?search_query=wnsautter&aq=f
Describes electrostatic principles and concepts.
**More good stuff available at:
www.wsautter.com
and
http://www.youtube.com/results?search_query=wnsautter&aq=f
A presentation on Coulomb-Blockade Oscillations in Semiconductor Nanostructures made by Deepak Rajput. It was presented as a course requirement at the University of Tennessee Space Institute in Fall 2008.
Application of Dielectric Spectroscopy to Monitor Insulating Materials ahmdfurkan
PDC measurements, it was found that polarization and depolarization currents increase with temperature increase. Also, the shape of polarization current changes as temperature increases
Drying of the transformer shows a significant reduction of the polarization/depolarization currents.
Moisture and aging have great effect on dielectric response of oil-paper insulation in frequency domain both of them will cause the increase of tan δ
Diagnostics of oil-paper insulation based on Frequency Domain Spectroscopy has great advantage over traditional techniques for its simple operation and non-destructive
Computation of Dielectric Constant and Loss Factor of Water and Dimethylsulph...Scientific Review
This study examined the computation of the dielectric constant (ε′) and dielectric loss factor (ε′′) of water and dimethylsulphoxide (DMSO)at temperature 20oc, 30oc, 40oc and 500C within the frequency range of f GHz using Debye equations. The Debye equations were derived, and the experimental values of the static dielectric constant (εs), dielectric constant at high frequency (ε ) and the relaxation time (τ) of water and DMSO at those temperatures were substituted into the derived equations and the dielectric constant (ε′) and loss factor (ε′′) of water and DMSO were computed with aid of maple-13 and results were generated. These results revealed that the method is capable of reproducing good results forwork done using single Debye and that of the reflection cell ofdimethylsulphoxide.
A presentation on Coulomb-Blockade Oscillations in Semiconductor Nanostructures made by Deepak Rajput. It was presented as a course requirement at the University of Tennessee Space Institute in Fall 2008.
Application of Dielectric Spectroscopy to Monitor Insulating Materials ahmdfurkan
PDC measurements, it was found that polarization and depolarization currents increase with temperature increase. Also, the shape of polarization current changes as temperature increases
Drying of the transformer shows a significant reduction of the polarization/depolarization currents.
Moisture and aging have great effect on dielectric response of oil-paper insulation in frequency domain both of them will cause the increase of tan δ
Diagnostics of oil-paper insulation based on Frequency Domain Spectroscopy has great advantage over traditional techniques for its simple operation and non-destructive
Computation of Dielectric Constant and Loss Factor of Water and Dimethylsulph...Scientific Review
This study examined the computation of the dielectric constant (ε′) and dielectric loss factor (ε′′) of water and dimethylsulphoxide (DMSO)at temperature 20oc, 30oc, 40oc and 500C within the frequency range of f GHz using Debye equations. The Debye equations were derived, and the experimental values of the static dielectric constant (εs), dielectric constant at high frequency (ε ) and the relaxation time (τ) of water and DMSO at those temperatures were substituted into the derived equations and the dielectric constant (ε′) and loss factor (ε′′) of water and DMSO were computed with aid of maple-13 and results were generated. These results revealed that the method is capable of reproducing good results forwork done using single Debye and that of the reflection cell ofdimethylsulphoxide.
BASIC ELECTRONICS
Electronics is a branch of physics that deals with the emission and effects of electrons in materials.
Or
Is a branch of science dealing with the study and development of circuit involving semi conductors, logic gates and other electrical components like resistors, capacitors and inductors.
2. Why is the conductivity of insulators
negligible, compared to semiconductor ?
It depends
on mainly
two factors ,
conductivity Atomic
bond
Energy
band
structure
3. conductivity
Insulator semiconductor
• valence electrons are tightly • Mostly covalent bonding
bound to (or shared with) the somewhat weaker bonding
individual atoms – strongest ionic • Electrons can reach the
(partially covalent) bonding. conduction band at ordinary
temperatures.
• The energy gap is too large when
• An electron promoted into the
compared to semiconductor. conduction band leaves a Hole
(positive charge) in the valence
band, that can also participate in
conduction.,
• The conductivity increases with
increasing temperature.
5. • The highest filled state at 0 K
Fermi Energy (EF) Band structure
• The two highest energy bands The energy difference
are: between the bottom of the
• Valence band – the highest band Conduction and the top of
where the electrons are present at 0 the Valence bands is called
K the Band Gap
• Conduction band - a partially filled
or empty energy band where the
electrons can increase their energies
by going to higher energy levels
within the band when an electric
field is applied
7. When enough energy is
supplied to the e- sitting at the
Empty
top of the valance band, e- can conduction
make a transition to the bottom band
of the conduction band.
When electron makes such a
transition it leaves behind a
missing electron state.
This missing electron state is
called as a hole. Hole behaves Energy e- e- e- e-
+ + + +
as a positive charge carrier. Full
Magnitude of its charge is the valance
band
same with that of the electron
but with an opposite sign.
8. Electron mobility
• Characterizes how quickly an electron can move
through a metal or semiconductor, when pulled by
an electric field, in semiconductors .
• When an electric field E is applied across a piece of
material, the electrons respond by moving with an
average velocity called the drift velocity V, Then the
electron mobility μ is defined as
|v| = μE
9. Vd E
E: applied field
: mobility of charge carrier
cm
2
Vd
is a proportionality factor
V Sec
E
So is a measure how easily charge carriers move under the influence of
an applied field or determines how mobile the charge carriers are.
10. How mobility depend on doping?
• Mobility is dependent on the drift velocity. The main
factor determining drift velocity (other than effective
mass) is scattering time. How long the carrier
is accelerated by the electric field until it scatters
(collides) with something that changes its direction
and/or energy.
• The most important sources of scattering in typical
semiconductor materials, discussed below, are ionized
impurity scattering.
11. Doping
Doping is the incorporation of [substitution] impurities into a
semiconductor according to our requirements.
In other words, impurities are introduced in a controlled
manner
Impurities change the conductivity of the material so that it
can be fabricated into a device
Doped crystals are extrinsic semiconductors. “adding minute
amounts of suitable impurities to the pure crystals”
Crystals are doped to be n type or p type
n type semiconductors have few minority carriers (holes).
p type semiconductors have few minority carriers (electrons).
12. • The purpose of semiconductor doping is to increase the
number of free charges that can be moved by an external
applied voltage..
• So the crystal has no resistance to current flow and
behaves as a superconductor. The perfect periodic
potential does not impede the movement of the charge
carriers.
• However, in a real device or specimen, the presence of
impurities, interstitials, subtitionals, temperature , etc.
creates a resistance to current flow.
13. probability of occupation
• The Fermi level or Fermi energy is the energy, at which the
probability of occupation by an electron (or hole) is exactly ½. In
semiconductor, usually, Fermi level is in the band gap.
•
• F(E )=1 ⁄ 1+exp[(E-EF) /KT ]
Where
• K = Boltzmann constant
• E F =Fermi energy or Fermi level
• T =0k
• F(E)=The probability that an electron state having
energy E is occupied