Download dielectric points

1. In designing of cheap, we never use contact transistor (because of improper input impedance and other
issues); we always use field effect transistor and generally use MOSFET. In MOSFET there is a
source layer and a drain layer (one of which is +ve) and the other one is -ve. In between these two
layers a dielectric layer is kept (in case of MOSFET) it is SiO2, but it can be other dielectric, too. This
is called gate dielectric, and now much efforts have been given in replacing SiO2, most of these
alternative dielectrics are high-kappa (pronounced as high-khey) dielectric. A dielectric having
dielectric constant greater than that of SiO2 is called high-kappa and the one having less than that of
Sio2 will be called low-kappa dielectric.
2. Our ECE Department has a software called EDS, which is used for design of micro-strip antenna,
and it leads to shape and thickness of different dielectric materials. The software yields some numbers
like for best efficiency we need a dielectric of dielectric strength A, dielectric constant B, etc. They
don't know how to check material database to locate that material, we just wish to provide them an
idea how to look at it. See very simple article attached as "Analysis of Five Different Dielectric
Substrates on Microstrip Patch Antenna" Section 3 of this provides a crude model where it is shown
that parameters of a microstrip Antenna depends on the dielectric constant. And appropriate choice of
dielectric constant and other material properties are very important for designing of Antenna. In the
above context please read intro and highlighted text of "Analysis and design of rectangular microstrip
antenna on two-layer substrate materials at terahertz frequency". Specially intro and highlighted text.
3. While we have shown the plot of epsilon'' (imaginary part), we have seen that it varies with frequency.
Further in context of dielectric loss and in general discussion we have mentioned that loss is
proportional to epsilon''. Thus, the plot shows that loss is a function of frequency and for transmission
of electromagnetic waves (which is nothing but alternating field) we need to choose frequency such
that loss is minimum. Now we can further note that optical fiber, being transparent, must be
dielectric and loss (attenuation) through it has to be a function of frequency. Incidentally the loss
is minimum in 1350nm-1550 nm and this is why all communication via fiber is done in this range and
this range is referred to as teleportation range.
4. Moore's law state that number of transistor in a chip doubles in every 18 months. If so transistors have
to reduce in size by reducing A/d or both. If you reduce d to avoid leakage or dielectric breakdown
you need high dielectric strength too. Consider that the distance between drain and source is 1
micrometer then and the voltage difference is 1 V, in that case required dielectric strength should be
greater than 1 million volt/m, which is high and such values are more expected in high kappa material.
Further, reduction of thickness of gate dielectric may lead to quantum effect like tunneling.
5. Dielectric plays important role in capacitor, an important circuit that needs attention is 1T/1C which
is made of 1 transistor and 1 capacitor. This connects many thing as such circuits are used in the
construction of FERAM (ferroelectric RAM), and circuits for controlling pixels of your monitor.
Specially, the transistors used in this ckts are thin film transistor. This is why our monitor are called
TFT.