Until now, much effort has been done on the fabrication of novel devices based on physics of quantum mechanics, principally using the nano-fabrication technique developed in semiconductor device technology. As a result, single electron tunneling (SET) devices using small particles in their systems have been successfully prepared. Nano-fabrication technology may lead to a revolution in the field of electronics, and many novel electronic devices such as high-density memory devices, high-speed low-power switching devices, and highly sensitive electrometer devices will be produced in near future. The study of observing specific functions of organic molecules and applying these functions to electronic and optical molecular devices is of crucial help because one can realize novel functional devices only by using organic molecules without using the maturing nano-fabrication technology in the field of semiconductor device technology. This chapter introduces single electron tunneling (SET) devices using organic molecules prepared by the Langmuir-Blodgett (LB) technique. For the realization of SET devices, it is necessary to design the device system so that the one-electron charging energy of e2/2C is greater than the thermal energy. In this sense, the so-called small particles, whose size is less than several nanometers, must be introduced into the molecular systems to be used. However, it is difficult to do this. Overcoming the difficulties, an attempt to use an organic mono-molecule as a so-called "Coulomb island" has been made. The chapter also describes single electron tunneling devices prepared using organic molecules.
All Science Journal Classification (ASJC) codes