A brief theory describing how one obtains the conductanceresistance of an n- typ
ID: 2266786 • Letter: A
Question
A brief theory describing how one obtains the conductanceresistance of an n- type resistor of some given semiconductor material, doping, geometry, and dimensions.2) Based on your discussion in (1) above, describe the use of the resistor structure in (a) magnetic sensing, and (b) optical sensing. A brief theory describing how one obtains the conductanceresistance of an n- type resistor of some given semiconductor material, doping, geometry, and dimensions.
2) Based on your discussion in (1) above, describe the use of the resistor structure in (a) magnetic sensing, and (b) optical sensing. A brief theory describing how one obtains the conductanceresistance of an n- type resistor of some given semiconductor material, doping, geometry, and dimensions.
2) Based on your discussion in (1) above, describe the use of the resistor structure in (a) magnetic sensing, and (b) optical sensing.
Explanation / Answer
a)
Current density in a semiconductor is given by … J=qnve+qpvh=q(nµn+pµh)
EJ=qnve+qpvh=q(nµn+pµh)E.................................................(equation 1)
Where q is charge on an electron, n and p are electron and hole density , ve and vh are drift velocity of electrons and holes respectively, E is electric field intensity in the semiconductor. Conductivity due to electrons and holes is obtained by…. In physics ..there is a version of Ohm's law given by....
where is conductivity of material.... comparing equation 1 and equation 2....
s=J/E=q(nµn+pµh)s=J/E=q(nµn+pµh)
conductance is given by ... S=sA/lS=sA/l where A is the cross sectional area and l is the length of semiconductor Resistivity is defined as the inverse of conductivity, so ?=1/s=1/q(nµn+pµh)?=1/s=1/q(nµn+pµh)
Resistance is given by R=?l/AR=?l/A Solution of part 2: Resistance is used as temperature sensor in following sensors: (a) Resistance Temperature Detector(RTD) (b) Thermistor (c) strain gage (d) thermocouple (a) Resistance Temperature Detector(RTD) : Metals resistance increase when their tamperature is increased. This property of metals is used to measure temperature . metals that are used to make RTD are platinum. nickal, copper. resistance of metals varies linearly with temperature. formula for resistance calculation using RTD is R=R0(1+aT)R=R0(1+aT) where R0 is resistance at T=0K and R is resistance at temperature T , aa temperature...
b)MAGNETIC SENSING:
Magnetometers can be categorized into four general types depending on the magnitude of the measured field. If the targeted B-field is larger than the earth magnetic field(maximum value around 60 µT), the sensor does not need to be very sensitive. To measure the earth field larger than the geomagnetic noise(around 0.1 nT), better sensors are required. For the application of magnetic anomaly detection, sensors at different locations have to be used to cancel the spatial-correlated noise in order to achieve a better spatial resolution. To measure the field below the geomagnetic noise, much more sensitive magnetic field sensors have to be employed. These sensors are mainly used in medical and biomedical applications, such as MRI and molecule tagging.
There are many approaches for magnetic sensing, including Hall effect sensor, magneto-diode, magneto-transistor, AMR magnetometer, GMR magnetometer, magnetic tunnel junction magnetometer, magneto-optical sensor, Lorentz force based MEMS sensor, Electron Tunneling based MEMS sensor, MEMS compass, Nuclear precession magnetic field sensor, optically pumped magnetic field sensor, fluxgate magnetometer, search coil magnetic field sensor and SQUID magnetometer.Magnetometer based on piezoelectric resonator can be applicable to flaw of the oil pipeline which is made of ferromagnetic material, such as iron. When the magnet create eddy current along the pipeline, such eddy current would generate magnetic field which can be sensed by magnetometer. If there is no flaw or crack in the pipeline, B field from eddy current would show constant pattern. But, if there is any flaw or crack inside the pipeline, B field would be changed. So, magnetometer can sense the change of B field
Magneto-mechanical effects; e.g., magnetostriction, and magnetometer.
Thermo-magnetic effects; e.g., Righi-Leduc effect. Galvano-magnetic effects; e.g., Ettingshausen effect.
Thermo-magnetic effects; e.g., Ettingshausen-Nernst effect. Galvano-magnetic effects; e.g., Hall effect, and magneto-resistance.
Magneto-optical effects; e.g., Faraday effect, and Cotton-Mouton effect.
OPTICAL SENSING:
The optical sensing is to directly measure the mechanical displacement of the MEMS structure to find the external magnetic field.
Zanetti et alfabricated a Xylophone beam. Current that is flowing through the center conductor and Xylophone beam mara will be deflected as the Lorentz force is induced. Direct mechanical displacement is measured by an external laser source and a detector. The resolution of 1 nT can be reached. Wickendenhad tried to shrink the footprint of this type of device by 100 times. But a much lower resolution of 150 µT was reported.
Keplinger et al were trying to use an LED source for optical sensing instead of using an external laser source. Optical fibers were aligned on the silicon substrate with different arrangements for the displacement sensing. A resolution 10 mT is reported.
Magneto-mechanical effects; e.g., magnetostriction, and magnetometer.
Thermo-magnetic effects; e.g., Righi-Leduc effect. Galvano-magnetic effects; e.g., Ettingshausen effect.
Thermo-magnetic effects; e.g., Ettingshausen-Nernst effect. Galvano-magnetic effects; e.g., Hall effect, and magneto-resistance.
Magneto-optical effects; e.g., Faraday effect, and Cotton-Mouton effect.
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