Project 1: Smallest nanoelectronic devices with precise atomic-scale structures

Project 2: Modeling of carbon nanotube devices - how similar to and different from silicon devices

Our ultimate goal is to develop nanoelectronics the future NASA mission relies on. In order to create "new" nanoelectronics based on a "traditional" circuit scheme, obtaining nanodevices with signal gain is mandatory. All the present devices with appreciable gain use either the gate modulation effect or the minority carrier injection effect and are made of semiconductors. We therefore place a special emphasis on the study of nanosemiconudctors, although nanometals are another interest for a "new" nanoelectronics based on a different circuit scheme. There are two physical systems we are particularly interested in.

(1) Adatom chains on an atomically regulated substrate

Due to the rapid progress in surface science, it is possible to create artificial atomic structures on a substrate. We have theoretically identified semiconducting and metallic adatom chains chemisorbed to the silicon substrate, and have clarified the condition that these chains are electronically isolated from the substrate regardless of the chemical bonds (PRB '99 & JVSTA '99). We are collaborating with Dr. D. Chen's experimental group of the Rowland at Harvard University and studying how these ideas come into reality.

(2) Semiconducting carbon nanotube devices

There have been a lot of reports for nanotube device experiments. We are comparing these nanotube devices with familiar silicon devices, and characterizing the nanodevices in general. Although nanotube and silicon devices are similar in many aspects, we have found one significant difference, i.e., a metallic electrode - semiconducting nanotube contact plays an essential role in nanotube devices in the device characteristics (APL '00, '01, & '02) while the contact effects are invisible in silicon devices due to the good Ohmic contact.