<< Chapter < Page Chapter >> Page >
Characteristics Symbol Units Ge Si GaAs Cu
Effective Density of States N c Cm^ -3 1.04×10^ 19 2.8× 10^ 19 4.7×10^ 17
N v Cm^ -3 6.1×10^ 18 1.02× 10^ 19 7×10^ 18
Energy Gap E g eV 0.68 1.12 1.42
Intrinsic Carrier concentration n i Cm^ -3 2.25×10^ 13 1.15× 10^ 10 1.6×10^ 6 8.5× 10^ 22
Effective mass m n (unit mass 9.11×10 -31 Kg) 0.33 0.33 0.068
m p (unit mass 9.11×10 -31 Kg) 0.31 0.56 0.56
Mobility μ n Cm^ 2 / (V-s) 3900 1350 8600 44
μ n Cm^ 2 / (V-s) 1900 480 250
Dielectric Constant ε r 16.3 11.8 10.9
Atomic Concentration Cm^ -3 4.42×10^ 22 5×10^ 22 4.42× 10^ 22 8.5× 10^ 22
Breakdown Field E BR V/cm 10^ 5 3×10^ 5 3.5×10^ 5

1.10.2.1. METALS ( with special reference to the mobility of conducting electrons and its implications for particle accelerators ).

Metal is a lattice of positive ions held together by a gas of conducting electrons. The conducting electrons belonging to the conduction band have their wave-functions spread through out the metallic lattice. The average kinetic energy per electron is (3/5)E F (This will be a tutorial exercise). Hence

=
1.93

where m* is the effective mass of the electron but we will assume it to be the free space mass.

Therefore:

……………. 1.94

Where

This velocity is not thermal velocity but velocity resulting from Pauli’s Exclusion Principle which essentially is the result of the ferm-ionic nature of electrons. Electrons tend to repel one another when confined in a small Cartesian Space. Electrons are claustrophobic.

Therefore mean free path =

…… 1.95

Where τ is mean free time.

Substituting the appropriate values for each metal, we get the mean free path for electron in their respective metals.

Table(1.10) Tabulation of the Fermi Energy, velocity, mean free time and mean free path of conducting electrons in their respective metals.

Metal E F Velocity(×10^ 5 m/s) τ (femtosec) L*(A°)
Li 4.7 9.96 9 90
Na 3.1 8.08 31 250
K 2.1 6.65 44 293
Cu 7.0 12.15 27 328
Ag 5.5 10.77 41 441.6

As we see from Table(1.10), the mean distance between two scatterers is 2 orders of magnitude greater than the lattice constant which is of the order of 5 A°. Hence lattice centers per se are not the scatterers but infact the disorderliness is what causes the scattering. The scatterers are thermal vibrations of lattice centers, the structural defect in crystal growth and the substitutional/interstitial impurities. This implies that with reduction in temperature mobile electrons will experience less scattering hence the metal will exhibit less resistivity leading to positive temperature coefficient of resistance. We will dwell upon this in Section (1.12).

1.10.2.2. SEMICONDUCTORS

Semiconductors are insulators initially. At low temperatures, all electrons are strongly bonded to their host atoms. Only at temperatures above Liquid Nitrogen that thermal generation of electron-hole pairs take place. So in semiconductors the situation is quite different as compared to that in metal. The conducting electrons and holes owe their mobility to thermal energy they possess in contrast to the conducting electrons in metal. On an average by Equipartition Law of Energy, the mobile carriers possess (1/2)kT thermal energy per carrier per degree of freedom. Since the carriers have 3 degrees of freedom hence they possess (3/2)kT average thermal energy per carrier.

Questions & Answers

how can chip be made from sand
Eke Reply
is this allso about nanoscale material
Almas
are nano particles real
Missy Reply
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
Lohitha
where is the latest information on a no technology how can I find it
William
currently
William
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Solid state physics and devices-the harbinger of third wave of civilization. OpenStax CNX. Sep 15, 2014 Download for free at http://legacy.cnx.org/content/col11170/1.89
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Solid state physics and devices-the harbinger of third wave of civilization' conversation and receive update notifications?

Ask