Unformatted text preview: MatE 153 Section 1
FINAL
Spring 2007
You have 2 hours & 15 minutes to complete this test. The test is closed book, closed
notes.
Show all your work! The neater and clearer your work is, the more partial credit you will
receive. Check all your math after you have completed the test. Read and sign the honor
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outside material during this test including my text or the work of my fellow students. I
will utilize no programmed in text or equations on my calculator. I realize that if I am
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receive a zero grade for this midterm and be reported through the University channels
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Print Name: ________________________________ 1 1. Name the two ways in lab that you experimentally determined the badngap energy of
a sample (5 points)
a.
b.
2. Compare allowed wavelengths for a free electron versus an electron in a box. (5
points) 3. A solid whose individual atomic magnetic moments normally point in random
directions but align in the direction of an applied field is (5 points)
a. Diamagnetic
b. Paramagnetic
c. Ferromagnetic
d. Ferrimagnetic
e. Antiferromagnetic 4. Describe in words or a sketch how to find the Bohr radius from the electron
wavefunction. (5 points) 5. What is the net spin magnetic moment (in terms of Bohr magnetons) for one atom
of Mn (Z=25) ? _________________ (5 points) 2 6. Use the attached data sheets and tables to answer this question. (5 points)
Which is true about the conductivity of intrinsic Si and intrinsic Ge at room temperature?
a.) σSi>σGe
b.) σSi<σGe
c.) σSi=σGe
d.) intrinsic material doesn’t not have a σ
7. Use the attached data sheets and tables to answer this question. (5 points)
Which is true about the conductivity of ptype Si doped with 1016 boron atoms/cm3 and
ntype Si doped with 1016 phosphorous atoms/cm3? Assume all the dopants are
ionized. (3 points)
a.) σSi,ntype>σSi,ptype
b.) σSi,ntype<σSi,ptype
c.) σSi,ntype=σSi,ptype
d.) can not be determined from the given data
8. An electron is confined to a three dimensional box of dimensions 20 nm by 20 nm
by 40 nm. What is the wavelength of an electron trapped at the E114 level? (10
points) 3 9. A solenoid is made by coiling an aluminum metal wire. The uncoiled
dimensions of the wire is 0.1 m long and 0.4 mm in diameter. When the solenoid
is coiled, it has 250 coils and is 0.05 m long. If the solenoid is heated to 600K,
what is the magnetic field generated if 2V is applied to it? (10 points) 4 Data is given below for the carrier concentration as a function of temperature in an ntype
Si sample.
1E+20 Ln n [atoms/cm^3] 1E+19 1E+18 1E+17 1E+16 1E+15
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008
1/T [K^1] 10. What is the saturation temperature? ________ (5 points)
11. What is the energy needed to ionize a dopant? ____________ (5 points)
12. What is the conductivity at 200K? _____________________ (5 points) 5 The valence band for the metal Cs (Z=55) at 0K is given below.
E=0, vacuum level 2.14 eV 1.58 eV 13. What is the Fermi energy at 500K? __________________ (5 points) 14. Calculate the probability of a state being occupied (full) at kT above the Fermi
energy (E=EF+kT) for 500K. (5 points) 15. If Cs is used as a target in a photoelectric experiment, what is the velocity of an
electron that is created when 400 nm of light is shone on the target?
__________________ (10 points) 6 There is a pn junction with 1019 atoms/cm3 dopants on each side. Assume all the
dopants are ionized at room temperature (300K). Assume that the space charge
region (depletion region at the junction) is 1 μm wide.
16. Calculate the diffusion coefficient for holes on the ptype side at 300K.
________________ (5 points) 17. .Calculate the builtin voltage across the junction at 300K.
___________________ (5 points) 7 ...
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 Fall '08
 Patel,N
 Magnetism, Magnetic Field

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