Nanoscale electronic devices -- Aiming to develop electronic devices for the future

In Keio University's Department of Electronic Engineering, the Uchida Group is working to understand physical phenomena that arise when electronic devices are fabricated at the nanoscale. The researchers aim to utilize the knowledge they obtain, to suggest ways of improving the performance of devices.

In today's information-intensive society, semiconductor large-scale integrated circuits play a key role in processing information. These integrated circuits contain billions of transistors, enabling them to implement various functions. Improving the performance of the electronic devices that make up integrated circuits leads directly to higher performance and lower power consumption in those integrated circuits. So, it's very important to increase the performance of electronic devices.

Q. It's very hard to predict how electronic devices will evolve from now on. But one possibility is enabling them to run at lower voltage; conversely speaking, unless devices can run at lower voltage, you don't get the advantage of lower power consumption, enabling your smartphone, say, to be used for a long time. So, what we hope for in future devices, or what we need to achieve, is to run them at very low voltage, so the power they consume is very low. That's a major trend. But regarding integrated circuits, until now, all they've had to do is compute, or store information. From now on, though, integrated circuits will have to relate to the outside world a bit more interactively. So, electronic devices won't just do computing with low power consumption; they'll also have to interact with the outside world. For example, we think integrated circuits may need to contain sensors or the like.

One effect that becomes important at the nanoscale involves interfaces between different materials. When objects become smaller, their surface area becomes larger compared with their volume. For this reason, physical phenomena that occur on surfaces or interfaces start to have serious effects on the characteristics of electronic devices. The Uchida Group aims to understand physical phenomena occurring at surfaces and interfaces in devices -- in particular, phenomena that affect device characteristics.

Q. When volume becomes very small, the ratio of surface area to the volume becomes proportionally larger. When that happens, phonons, which carry heat from one point to another , are scattered on the surfaces or interfaces, and as a result, heat conductivity becomes lower. At another aspect, electric currents generate heat, which means that electrical energy gets converted to vibrational energy in the crystal lattice. Observed on the nanoscale, in fact, such a transfer of electrical energy to the crystal lattice is by no means a very local effect. To some extent, when observed on nanoscale dimensions, things you'd normally expect to observe in one place happen in a slightly different place. Because phenomena like that occur, to understand how heat is generated at the nanoscale becomes a touch task.

As well as that type of research, the Uchida Group is studying atomic-scale layers of graphene, which has the potential to replace silicon in electronic devices, because it provides advantages on the nanoscale. This research concerns the possibility of applying such layered materials to devices. In these ways, the Uchida Group continues to tackle new challenges, with a view to developing devices for the future.