Lauri Jaakkola
Metropolia Ammattikorkeakoulu
4.5.2017
Task 3: LEARNING DIARY 1 Matter and conductivity
SUGGESTIVE QUESTIONS TO ANSWER:
1) Do charged and polar (or easily polarizable) units have any meaning for electric
conductivity?
The resistance continues to decrease as the charge carrier density in the conduction band increases.
In extrinsic (doped) semiconductors, dopant atoms increase the majority charge carrier
concentration by donating electrons to the conduction band or producing holes in the valence band.
2) What are the significant atomistic factors of electric conductivity?
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Electrons are in different bands
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Doping
The addition of small quantities of an element (an impurity) to a pure semiconductor to
change its electrical conductivity characteristics.
An n-type semiconductor is a doped semiconductor in which conduction is due to the
movement of additional electrons and in p-type semiconductor conduction is due to the
movement of positively-charged holes.
Most common semiconductor components are diodes and transistors.
Lauri Jaakkola
Metropolia Ammattikorkeakoulu
-
4.5.2017
Electric configuration
Electrical conductivity occurs because of the ease with which electrons can be removed
from atoms. All substances consist of atoms. In turn, all atoms consist of two main parts: a
positively charged nucleus and one or more negatively charged electrons.
The electrons in an atom are not all held with equal strength. Electrons close to the nucleus
are strongly attracted by the positive charge of the nucleus and are removed from the atom
only with great difficulty. Electrons farthest from the nucleus are held only loosely and are
removed quite easily.
3) How does the solid state change the electric conductivity?
In solids, ions typically occupy fixed positions in the crystal lattice and do not move. However,
ionic conduction can occur, especially as the temperature increases.
Solids can conduct electrical charge due to the motion of electrons and the positive holes (electronic
conductivity) or because of the motion of ions (ionic conductivity). The reason for electrical
conductivity of metals is the motion of electrons and it increases by increasing the number of
participating electrons in the process of conduction.
Pure ionic solids, in which conduction occurs only through the ionic motion, are termed as
insulators. The defects in crystal structure increases the conductance property of semiconductor and
more so with insulator. The electrical conductivity of metals, insulators and semiconductors can be
explained in terms of Band Theory.
4) What about the electric conductivity of fluids (liquids and gases)
In electrolytes, electrical conduction happens not by band electrons or holes, but by full atomic
species (ions) traveling, each carrying an electrical charge. The resistivity of ionic solutions
(electrolytes) varies tremendously with concentration – while distilled water is almost an insulator,
salt water is a reasonable electrical conductor. Conduction in ionic liquids is also controlled by the
movement of ions.
At atmospheric pressure, air and other gases are poor conductors (Insulators) of electricity. Because,
they don't have any free electrons to carry current. But, once the free electrons are produced in gas
by ionization (they become plasmas), electric discharge occurs.
5) Nanomaterials and electric conductivity?
Carbon nanotube becomes one of the most promising materials in recently developed materials on
account of its superior properties of rigidity, strength, elasticity and electric conductivity.
Lauri Jaakkola
Metropolia Ammattikorkeakoulu
4.5.2017
Conductivity of a multiwalled carbon nanotube is different than that of single nanotube of same
dimensions.
The carbon nanotubes can act as conductor or semiconductor in behaviour. Large carbon (graphite)
is good conductor of electricity.
6) Which technical factors are used to improve electric Conductivity?
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Doping
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Electroplating
Electroplating helps improve conductivity of a raw part by enhancing its electrical
properties. Electroplating can impact durability, contact resistance, solderability and
corrosion resistance. When designing components for applications where conductivity is of
importance, the surface finish should be chosen such that the conductivity value is
appropriate for the application, for example gold or silver.