Electrical Properties
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does the 2s electron state break into individual energy bands at a smaller or larger interatomic separtation than 1s
at a larger separation
what do electrical properties depend on?
the arrangment of the outermost electrons and how theyre filled with electrons
which electrons will be accelerated when an electric field is passed through them
only the ones with an energy greater than the fermi energy
what does the electrical conductivity depnend on?
the number of free electrons and the number of holes
how do metals access nearby energy states
by thermal fluctuations
what is the relationship between the band gap and the electrical conductivity
the larger the gap, the lower the conductivity
How can we decrease resistivity (3 ways)
of impurities, temperature, %Cold Work
which type of imperfections increase resisitivity (4) for metals
• grain boundaries • dislocations • impurity atoms • vacancies
why do imperfections increase resisitivity
because they force the electrons to take a less direct path
why does increasing temp increase resistivity
because it causes the atoms to vibrate more, making it harder for the electrons to move through them
why does increasing %CW increase resistivity
because it increases dislocation concentration
formula for electrical conductivity
1/rho(resistivity)
what are the types of charge carriers in insulators and semi conductors?
Free electrons and Holes
Describe free electrons:
-have negative charge and are located in the conduction band
describe holes:
have positive charges and are located in the valence band
for semi-conductors what is the relationship between temperature and electrical conductivity
as T increases, conductivity increases
for an intrinsic what is the ratio between number of electrons and the number of holes
they are equal
how would we create EXTRINSIC conduction
by adding impurites with different # of valence electrons than the host atom
what is the main difference between intrinsic and extrinsic conduction
the number of electrons does not equal the number of holes
what are the 2 types of extrinsic conduction and describ
N type and P types N types: N>P P type P>N
If we have donor impurities what is the case:
N type; negative conductivity by electrons
if we have acceptor imupurites what is the case:
P types; positive conductivity by holes
How can we control the conductivity
by controlling the concentration of donors/acceptors
where is the donor impurity energy level located
just below the conduction band