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The Chemistry of the Electronics Industry
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Why do we use semiconductors in electronics?
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<strong>The main reason semiconductor materials are so useful is that
the behavior of a semiconductor can be easily manipulated by the
addition of impurities. This is known as doping. Semiconductors are used
to make sensors in electronics because the conductivity can be
controlled by introducing an electric field, exposing it to light, and
by applying pressure and heat. Doping a semiconductor such as silicon
with a small amount of impurity atoms, such as antimony or boron,
greatly increases the number of free electrons or holes within the
semiconductor which, in turn, increases the semiconductor's conductivity.</strong><br><font size="2">http://en.wikipedia.org/wiki/Semiconductor_device
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How are semiconductors useful <strong>and </strong>what are they
commonly used for?
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How is current conducted in a semiconductor?
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<strong>Because a silicon atom can form four covalent bonds with four
other silicon atoms, if a dopant composed of atoms with five valence
electrons (e.g. antimony Sb) is added to a silicon crystal, then only
four of the electrons can pair up with electrons from silicon atoms to
form covalent bonds, leaving one free to move. The allows an electric
current to be produced. The free electrons are marked yellow so that you
can see them. Note that the dopant concentration is greatly exaggerated. </strong>
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How is current conducted when antimony is used as a dopant?
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<strong>If a dopant composed of atoms with three valence electrons (e.g.
boron B) is added to a silicon crystal, then one of the four covalent
bonds is short an electron, leaving a hole which also results in an
electric current. Note that the dopant concentration is greatly
exaggerated. </strong>
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Watch the running model and explain, in your own words, what "holes" are
and how they allow for conduction of electricity.
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How does doping silicon with boron increase the conductivity of silicon?
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<strong>To summarize:</strong><br>How does the atomic structure of a
dopant contribute to its ability to conduct electricity. Be specific
regarding number of valence electrons and the impact on free electrons
and holes?
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