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 Nano electronics is the emerging field in the present world. Single electron devices plays a vital role in developing various electronics devices using nano technology. Single electron transistor(SET) is the device, which operating based on the principle of coloumb blockade. Using the SET here we are going to construct the circuit, which accepts a 3 bit binary number and produces a output, which is equal to the square of the corresponding decimal no. This circuit consumes less power and area. INTRODUCTION Single electron devices are the basic devices in the nano electronics field these devices mainly works on the principle of couloumb blockade and control the charge transfer in terms of controlling electrons. The single electron devices are mainly of following types. Single electron box, single electron trap, and single electron transistor, single electron turnstile. Each type have their own applications In various fields. Especially in digital electronics side they are playing good role. Which replaces MOS transistors and used to construct various digital circuits COLOUMB BLOCKADE:- The basic concept of single-electronics is Coulomb blockade. Consider an electro neutral small conductor, which is called an island. The island has exactly as many electrons as it has protons in its crystal lattice. The electro neutral island does not generate any appreciable electric field beyond its borders and a weak external force can bring an additional electron from outside into the island. Now the net charge Q of the island is –e, where e is the elementary charge. The energy Ec to charge an island with an electron is called Coulomb energy and is given by: E=e2/2ci where Ci is the capacitance of the island. Though the extra charge -e in the island is very small, the electric field generated by this charge is inversely proportional to the square of the island size and may became very strong in nano scale structures. If the island is a 10 nm sphere in the of a single or a small number of electrons at conducting islands. In order to keep an extra electron confined into an island the Coulomb energy must be greater than the thermal energy, otherwise thermal fluctuations may drive the electron outside the island, i.e. the necessary condition is: E=e2/2ci>KBT where kB is Boltzmann’s constant ant T is the absolute temperature. For example, for an 100 nm scale device the electrons are kept inside the island if the temperature is about 10 K. However, the island size is reducing rapidly and at island sizes of about 10 nm the electron will be confined into them at room temperatures

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