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  1. This velocity can be thermal velocity or Pauli Velocity.

Answers: Conducting electron is strongly scattering in metallic crystalline lattice but very wekly scattering in Semiconductor as exhibited by short Mean Free Path in metals and by long Mean Free Paths in Semi-conductors.[1/4+1/4=1/2]

XXV. In the Table given in Question XIV which is Pauli Velocity and which is Thermal Velocity?

Answers: Conducting Electron velocities in Metals are Pauli velocities because they arise out of Pauli-Exclusion Principle whereas conducting electron velocities in Semi-conductor are thermal velocities.[1/4+1/4=1/2]

XXVI. In Question XVIII, intrinsic Ge has the least resistivity and intrinsic GaAs has the maximum , Why? Answers; Ge has the least Band-Gap and GaAs has the widest Band-Gap.[1/4+1/4=1/2]

XXVII.

This is what statistics and does it tell. At T= 0 Kelvin what kind of distribution is it? Answers: This is Fermi-Dirac Statistics, P(E) gives the probability of occupancy of E by Fermions, and Absolute Zero the distribution is RECTANGULAR.[1/6+1/6+1/6=1/2 Points]

XXVIII.

What is this expression ? Define all the terms. Answers: N(E)→Density of States per unit energy, (E-E C ) →kinetic energy of conducting electron in conduction band.[1/4+1/4=1/2]

XXIX. If Ultra-Violet light of λ = 0.2μm is incident on a metal then which of the metals listed in the Table below will respond and emit electrons ? Answers;UV photon has 6.2eV hence it is powerful enough to cause photo-emission in all the Metals listed in the Table below.All the metals have a work-function less than 6.2eV.[1/2 Poiint]

Metal Work-function Metal Work-function
Na 2.3eV Ca 3.2eV
K 2.2eV Ba 2.5eV
Cs 1.8eV Pt 5.3eV
W 4.5eV Ta 4.2eV

XXX.

Answers: This expression tells how EXCESS CARRIERS decay with respect to time in Semiconductors with excess carrier life-time or excess carrier relaxation time defined as τ n . Excess carriers exponentially decay with time. If relaxation time is long then excess carriers transient takes a long time to decay.[1/2 points]

Question 2.Describe the step for preparing Electronic Grade Poly-crystal Silicon from sand.

[7.5 marks]

Answer:

Reduction of sand with carbon gives impure polycrystalline Silicon

Reaction of pulverized raw silicon with HCl gaseous vapour to form TriChloroSilane

Multiple distillation of TriChloroSilane to obtain purified electronic grade TriChloroSilane

Thermal decomposition of SiHCl3 at 1000 degree centigrade in Sieman’s reactor to obtain fattened rods of electronic grade Silicon

Question 3. Balmer Series Spectral Lines from Stars are determined to be at 6563A°,4862A°,4341A°,4102A° and 3970A°. Determine these spectral lines theoretically.

[By the Red-Shift of these Balmer Spectral Lines the velocity of the receding Galaxy is detyermined. The recession velocity gives the distance of the Galaxy using Hubble’s relationship][7.5 marks]

Answer: λ(μm)=1.24/E g (eV) here E g = (13.6eV/4-13.6/n^ 2 )eV. Since the answer is to be obtained in Angstrom therefore the final expression is:

Therefore λ(Angstrom)=( (1.24/(13.6/4-13.6/n^ 2 ))×10^ 4 )Angstrom.

For n=3 to n=2, λ=6564.71A°;

For n=5 to n=2, λ=4862.75A°;

For n=6 to n=2, λ=4341.74A°;

For n=7 to n=2, λ=4102.94A°;

For n=8 to n=2, λ=3971.24A°;

Question 4.Detrmine the temperature at which E=E F +kT will be occupied by electron with P(E)=1%.[7.5 marks]

Answer

This question is wrongly stated. At E=E F +kT the Probability of occupancy is 1/(1+e) =0.2689. It can be never 1% irrespective of temperature.

The correct question is: Determine P(E F + kT) in Fermi-Dirac Statistics. Determine Temperature T at which P(E F + 0.5eV) = 1%.[Answers: 0.27, 1262Kelvin]

You can give either of the answers and fetch full marks.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Electrical and electronic materials science. OpenStax CNX. May 01, 2014 Download for free at http://cnx.org/content/col11615/1.14
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