During the past ten years, electron tunneling devices such as Josephson junctions and single electron tunneling devices have been fabricated using organic thin films, where the successful preparation of polyimide Langmuir-Blodgett (PI LB) films has made a significant contribution. The electrical properties of PI LB films were also examined carefully, and electrostatic phenomena, interfacial phenomena, electrical breakdown behaviors and so on have been elucidated. Based on these studies, the effects of space charge and coupling capacitance upon the operation of single electron tunneling (SET) devices using organic molecules have been investigated. The equation of step voltage is derived taking into account space charge and coupling capacitance, using an equivalent circuit model. It was concluded that knowledge of interfacial phenomena is very important for a better understanding of the operation of such devices.

Keywords
single electron tunneling, polyimide, space charge,