ABSTRACT
Single-electron transistor (SET) devices are of immense interest because of their potential for lowpower operation and high integration density. The basic building blocks of a SET device are tunnel junctions with very small capacitance that are connected in series with a central conducting island. Charge conduction occurs through two tunnel junctions that are connected to the source and drain terminals of the device. As the dimensions of the conducting island reduce to a few nanometers, the electronic wave functions in the conducting island become discrete. The discrete charge on the conducting island is accessed by tunneling through source and drain terminals. The central conducting island is capacitively coupled to a gate terminal, which is used to control the charge on the island. SET devices operate on the principle of a Coulomb blockade, which is the suppression of electron tunneling below a threshold voltage; the capacitance of the tunnel junction system dictates the threshold voltage, whereas a Coulomb blockade is observed when the device dimensions are reduced to a few nanometers [1]. SET devices can be realized with semiconducting or metallic systems. This chapter looks at metallic systems where tungsten and tungsten oxide are used. A pictorial view of a double-junction SET device is shown in Figure 14.1, where the conducting island is 182sandwiched between the two tunnel junctions that are connected to the source and drain terminals. One tunnel junction is characterized by the tunnel resistance Rt1 and capacitance C1, whereas the other tunnel junction is characterized by the resistance Rt2 and capacitance C2, and the capacitance of the gate coupled to the central conducting island is Cg. The energy required to add an electron to the conducting island is the charging energy, and the external applied bias provides energy for tunneling. If the applied bias is greater than the charging energy, it results in electron tunneling. Pictorial view of the double-junction SET device. https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9781315216089/1a39fa69-e426-4ca1-a1b7-b7d35c28e418/content/fig14_1.tif"/>
