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1.10.2. SOLID STATE OF MATTER.

With the development of Quantum Mechanics, Band Theory of solid was proposed by Felix Bloch[Appendix XXXXIII]. As already seen in the last section, electrons in a single crystal solid occupy energy bands separated by forbidden zones known as Band Gaps as shown in Figure(1.40) , Figure(1.41) and in Figure(1.49).

The outer band is known as the conduction band and the band just below is valence band. In insulators and semiconductors, the energy band gap between valence and conduction is wide of the order of eV and conduction band is completely empty at low temperatures for both insulators and semiconductors. That is at 77K (liquid Nitrogen temperature) and below, semi-conductor is an insulator. Only near room temperature and by introduction of controlled amount of impurities that semiconductor acquires a certain degree of conductivity. As we will see in semiconductor chapter the effective density of states at the lower edge of conduction band (N C )

and at the upper edge of the valence band (N V ) is nearly the same as shown in Table(1.10). This is of the order of 10^ 19 permissible states per centimeter cube. Hence as soon as doping approaches this order of magnitude, number of conducting electrons are comparable to the available energy states which is the criteria for degenerate systems. Hence at that order of magnitude of doping, semiconductor becomes degenerate and behaves like a semi-metal.

So an INSULATOR can be defined as the solid which has an empty conduction band and a large band gap , of the order of 4eV or more. There electron- hole pair cannot be thermally generated . Hence it remains non-conducting at all temperature.

On the contrary, SEMICONDUCTORS are non conducting and hence insulator below liquid Nitrogen temperature and above liquid Nitrogen temperature they acquire conductivity either due to thermal generation of electron-hole pair or due to contribution of conducting electrons by net donor atoms or due to holes contributed by net acceptor atoms.

Metals have partially filled conduction band or overlapping conduction and valence bands. As a result, there are mobile electrons available in copious amount. This amount is of the order 10 22 per centimeter cube. As we see in the Table(1.10), atomic concentration in Solids are of the order of 10 22 per c.c. and each atom contributes an electron for conduction. Hence availability of conduction electrons is 12 orders of magnitude greater than intrinsic Silicon and 9 orders of magnitude greater than that of intrinsic Germanium. Because of this large number of mobile carriers present in metal that resistivity is so much lower in metal than that in semiconductor. This point will become clearer as we proceed with the quantum-mechanical interpretation of conducting electron in metal or in semi-conductor.

As seen in Table(1.10) , the mobility of conducting electrons in semiconductors is much higher than that in metal which is typically 44cm 2 /(V-sec) for Copper.

Table(1.10) Characteristics of Ge, Si and GaAs at 300 K.

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
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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
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