Preface

The second half of the twentieth century and the beginning of the twenty first have been characterized by the most impressive industrial revolution ever seen. In approximately 40 years, the complexity of integrated circuits (ICs) has increased by a factor of 10, with a corresponding reduction of the cost per bit by eight orders of magnitude. Not only has this evolution allowed dramatic progress in all scientific fields (large computers, space probes, etc.), but also has fueled the economic development with the raise of new markets (personal computers, cellular phones, etc.) and even social revolutions (world wide web, global village, etc.). In last years, however, the situation has significantly changed: the continuous scaling down of device size has eventually brought the IC major technique, photolithography, to its limits. Overcoming its original limits has been proved to be possible, but the price to pay for that has changed the playing rules – while at the beginning of the IC history the evolution was driven by technology, now it is driven by economy, the cost of a medium size production plant being in the range of a few billion dollars. The predicted evolution is based on the assumption that future ICs will be based on the same basic constituent, the MOS-FET (metal–oxide–semiconductor fieldeffect transistor), suitably scaled to smaller and smaller sizes. The International Technology Roadmap for Semiconductors (the “Roadmap”) has thus identified which progress is necessary to allow the increase of IC complexity to continue with the current exponential growth. The number of researchers involved in the actions identified by the Roadmap is huge (about 10) and it is certainly possible that the limits it has identified will be beaten, but the cost of IC production plants is expected to increase by one order in a decade, putting it beyond the economic possibilities of most players. In the light of these considerations, alternative solutions to the current topdown evolution of ICs have been considered. In particular, the fast development of nanotechnology (permitting the control of size effect, self-assembly, hydrophobic– hydrophilic properties, etc.) and the discovery of exploitable conformation, charge storage, and conduction properties of single molecules ( -conjugated moieties, rotaxanes, proteins, etc.) have attracted a large interest, suggesting the possibility of developing nanoelectronics in a different fashion – bottom-up.