For the past 40 years, since the invention of the integrated circuit, the number of transistors on a computer chip has doubled roughly every 18 months. As the limits of photolithography are rapidly approached, however, it is becoming clear that continued increases in circuit density will require fairly dramatic changes in the way transistors are designed and operated. This review summarizes current strategies for fabricating transistors which operate based on the flow of single electrons through nanometre-sized metal and semiconductor particles; i.e. single electron transistors (SETs). Because the room temperature operation of SETs requires nanoparticles <10 nm in diameter, we focus mainly on devices which have the potential for being assembled from the solution phase (non-lithographic systems). Several applications of SETs are discussed in addition to the major hurdles which must be overcome for their implementation in electronic device technology.
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