Single Electron Transistor

Single Electron Transistor

1

Single Electron TransistorKhemendra Shukla

M.Sc. Applied Physics

BBAU Lucknow


2 Outline

What is a SET

Operation of SET

Coulomb Blockade

Why use SET

Application of SETs

Conclusion


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 .

What is SET?

http://en.wikipedia.org/wiki/File:Set_schematic.svg


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.

Operation of SET- How does SET work?


5

Conductor Dimension & mean free path of electron

Discrete electronic configuration allows one electron to tunnel at specific

conditions.

Coulomb Blockade

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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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.

Coulomb Blockade: Coulomb staircase


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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,

kTC

e

2

2

C

eVbias

22 e

hRT

Conditions for Coulomb Blockade


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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.

Why do we use SET ?

Insulating state 1e-

Conducting state SET


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Quantum computers -1000x Faster

High Sensitivity Electrometer

Single-electron memory

Single-electron logic systems

Carbon nanotube SET

Application of SET


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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


11Thank YOU

Science

Single Electron Transistor