Katsuhiko Nishiguchi Nanodevice's group
Physical Science Laboratory
NTT Basic Research Laboratories


 WhyNew Applicatsions?
  We have used a lot of electronics products, which support our life. To get more comfortable, useful, and friendly life, performance of electronics products has been improved by a continuous development of various kinds of technology. On the other hand, such development becomes more and more difficult. One of the most familiar, used, and powerful devices in electrical circuits is a transistor. Its performance has been increased by shrinkage of the transistor. However, since such shrinkage gives rise to various kinds of problems, e.g, the uncontrollable operation and high power consumption of the transistors, a lot of efforts have been focused on the need to achieve further improvement of the transistor, and such a trend will continue. Our research is a development of a new type of applications using new devices and circuits, whose mechanisms are quite different from present transistors and electrical circuits. In order to achieve it, we focus on nanometer-scale devices constructed by various kinds of fabrication processes of silicon transistors.

How to useNew Applicatsions
    One approach to a new application is to use one electron as one bit of information in the circuit. To achieve it, we must control single electrons precisely. Since conventional devices cannot control single electrons, we use single-electron devices. Among them, a one-by-one electron transfer device composed of transistors is useful due to its geometrical simplicity (see another page). On the other hands, single electrons must be detected to use them as data. The single-electron detection can be achieved by a high-charge-sensitive sensor using nanometer-scale transistor (see another page). The combination of the one-by-one electron transfer and sensing devices provides some applications, e.g., a multilevel memory (Electron. Lett., v. 40, p. 229, 2004) and a digital-analog converter(Appl. Phys. Lett., v. 88, p. 183101, 2006), in which one bit of information is represented by one electron.

  Another application is a circuit with high flexibility. Conventional circuits have powerful performance to give a precise answer/calculation according to particular algorithms. However, when a question is complicated, it takes long time to give the answer. The case that the algorithm is not optimized to the question also provides the conventional circuit with hard work. On the other hand, although a human brain may lack the precision to give the answer, flexibility of the human brain allows time- and power-efficient performance. Therefore, addition of flexibility to the circuits promises for high-efficiency electrical circuits. In our research, the flexibility is represented by random movement of single electrons flowing through a transistor (Nanotechnology, v. 20, p. 175201, 2009).