Page 285 - An Introduction to Microelectromechanical Systems Engineering

264 Glossary

semiconductor by adding electrons or holes (carriers). At or near room temperature,
the carrier concentration is largely equal to the dopant concentration. If the doping
is n-type, then there is an excess of electrons. Conversely, a p-type material has an
excess of holes. The material is electrically more conductive at higher doping levels.
A p-type region in direct contact with an n-type forms a p-n diode, which passes
current only in one direction: from the p-type to the n-type. Arsenic and phospho-
rous are common n-type dopants in silicon; boron is a p-type dopant in silicon.
Duality A general abstract concept that pairs equivalent parameters from dis-
tinct physical systems on the basis of energy arguments. Duality is frequently
invoked between mechanical, thermal, and electrical systems. For example, a spring
in a mechanical system is dual to a capacitor because they both store poten-
tial energy. In general, duality pairs mass to inductance, spring constant to the
inverse of capacitance, coefficient of viscous damping to resistance, mechani-
cal displacement to charge, velocity to electrical current, and applied force to
applied voltage.
EEPROM An acronym for electrically erasable and programmable read only
memory, a type of read-only electronic memory that can be erased and repro-
grammed using high-voltage electrical pulses.
Electromagnetic interference (EMI) Undesirable interference with electronic sig-
nals of an electromagnetic nature. Sources of EMI include solar eruptions, radio sig-
nals, and nuclear explosions.
Electrophoresis In chemistry, it is the migration of charged or polar molecules in
suspension in a solution under the effect of an externally applied electric field. It is
useful for the separation of dissimilar molecules and analysis of their molecular
structure based on their rate of movement.
Epitaxy Chemical process to grow a thin crystalline layer on top of a crystalline
substrate. The grown layer generally has the same crystalline orientation as the
substrate.

Etalon Also known as a Fabry-Perot cavity or etalon, it is an optical resonator
bounded by two partially reflective surfaces. At resonance, the length of the cavity
equals an integer number of half wavelengths. The etalon is a useful optical filtering
element.
Eutectic point At their eutectic point, alloys have identical solidus and liquidus
temperatures. The melting temperature of a eutectic alloy is lower than that of any
other alloy composed of the same constituents in different proportions. See liquidus
temperature.
Exponential probability density function A commonly used probability distribu-
tion in reliability applicable to components with a constant failure rate.

Filter An electrical or optical circuit that selectively blocks the transmission of
certain frequencies (or wavelengths). The transition frequencies defining the bands
of transmission are known as corner frequencies. A lowpass filter blocks high fre-
quencies but permits the transmission of low frequencies. A highpass filter performs
the opposite function of a lowpass filter. A bandpass filter allows the transmission of