# Every IC used today has logical Gates, all made of SET- the Single Electron Transistor.

As the name suggests, single electron transistor is a transistor where the operation principle is influential

only with the help of a single electron. Well, it may awe struck all the emerging engineering students that

how will it be possible to compensate a complete operation with help of a single electron? When looked

at the basics, traced back to the times when we got acquainted with ‘atom’, the concepts of neutrons,

electrons and protons was then introduced to us. With are developing grades we were later introduced to

many other subatomic particles such as mesons etc. Thus, the complete study of these subatomic particles

can further be defined under a completely vast domain ‘NANOTECHNOLOGY’. SET is thus one of the

subset under nanotechnology that holds its key references in many applications. Here are few interesting

and basic applications of single electron transistor that are defined in brief:

*A. Logic:*

In recent advances substitute for MOSFET’s in conventional Logic gates comprises of SET’S. This is due to the

special property that the SET’s have of not directly generating the currents even when coulomb blockade and

coulomb oscillators are dominant features. SET based logic and Charge state Logic are the two categories of logic

for single electron devices. The tunneling effect produces current incase of single electron devices. The

accumulation of plural electron results in voltage that is used to represent the corresponding bit. SET-based logic

circuits, such as Inverter, NAND and XOR gates, have been demonstrated on Si-based researches. In case of charge

static logic, the logic is represented by the corresponding elementary charge the bit of the charge state logic is

represented by the elementary charge. The representative devices are quantum cellular automation (QCA) and

single-electron binary decision Diagram (BDD)

**B. Super-sensitive electrometer:**

One of the main characteristics of SET is that it is highly sensitive in nature. Hence adopting this characteristic,

SET’s are widely used as supersensitive electrometer in study of physics. It is thus possible to measure very low DC

currents of the order of 10 ^ -20A with the use of this electrometer. Measurements in the study of single electron

effects, single – electron box and traps is also possible. The fractional charge excitation incase of fraction Quantum

Hall Effect was initially found due to the use of this electrometer

**C. Charge sensors:**

The SET’s are capable of analyzing the spin or qubits in case of Quantum Dots. Two silicon quantum dots were

fabricated using a lithographic process, on a single – on insulator substrate, where their capacitive parameters that in

turn related to signal to noise ratio (SNR ratio) were calculated. The theoretical capacitive parameters that were

obtained by direct imaging of the quantum dots were thus compared with the measured values. The analysis was

conclusive of the fact that on account of decreasing of SET diameter, it is possible to decrease the capacitive

coupling between the qubits but increase the SNR ratio and radio frequency single shot measurement. As these

results are independent of the device materials, it was thus possible to establish guidelines for the design of SET

charge sensors in lateral QD-SET structures based on a two-dimensional electron gas.

**D. Single Electron Spectroscopy:**

It is possible to measure the energy distribution levels in case of quantum dots by the use of single electron

spectroscopy where in SET’s are used. This can be achieved by capacitive coupling single – electron box wherein

the quantum dot is considered as the island to Single electron transistor and measuring the gate voltages which in

turn demonstrates sharp increase of source drain conductance