2. What is a SET
Operation of SET
Coulomb Blockade
Why use SET
Application of SETs
Conclusion
Single Electron Transistor
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3. Nano crystals of Nano scale diameter, exhibit quantum
effects.
The channel is replaced by a small dot.
The nanoparticle is separated from the electrodes by
vacuum or insulation layer.1
The gate voltage Vg is used to control the charge on the
gate-dot capacitor Cg .
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4. The tunnel junction consists of two pieces of metal separated by a very
thin (~1nm) insulator.
The only way to tunnel is through the insulator.
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5. Conductor Dimension & mean free path of electron
Discrete electronic configuration allows one electron to tunnel at specific
conditions.
When we start to increase
V from zero, no current can
flow between the
electrodes untill
Current start to flow
through the
nanoparticles only when V
is such that eφ>Ec
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6. When one electron overcome the charging energy and tunnels into
the quantum system, it blocks the tunnelling of a second one since it
would charge additionally the quatum system by an amount e2/2C.
The effect is that one electron tunnels at a time.
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7. The thermal kinetic energy of the electron must be less than the Coulomb
repulsion energy which will lead to reduction in current leading to blockade.
The bias voltage must be lower than the elementary charge divided by the self-
capacitance of the island
The tunneling resistance RT derived from Heisenberg's uncertainty principle,
Single Electron Transistor
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kT
C
e
2
2
C
e
Vbias
2
2 e
h
RT
8. It consumes less power for operation.
The coulomb blockade effect: an alternative operating principle for
nanometre-scale devices.
reduced circuit power dissipation.
raising the possibility of even higher levels of circuit integration.
Insulating
state
1e-
Conducting
state SET
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9. Quantum computers -1000x Faster
High Sensitivity Electrometer
Single-electron memory
Single-electron logic systems
Carbon nanotube SET
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10. With all the exciting properties of single electron devices, the pace of large
scale integration can continue.
Only one thing is certain: if the pace of miniaturization continues unabated,
the quantum properties of electrons will become crucial in determining the
design of electronic devices before the end of the next decade.
Researchers may someday assemble these transistors into molecular
versions of silicon chips , but there are still formidable hurdles to cross.
SETs could be used for memory device, but even the latest SETs suffer
from “offset charges”, which means that the gate voltage needed to achieve
maximum current varies randomly from device to device. Such
fluctuations make it impossible to build complex circuits.
Conclusions
Single Electron Transistor
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