Site: Electrotechnical Laboratory (ETL)
Ministry of International Trade and Industry (MITI)
1-1-4 Umezono, Tsukuba-shi
Ibaraki 305, Japan
Tel: (81) 298-54 5220; Fax:(81) 298-54 5088
Date Visited: 22 July 1997
WTEC: R.W. Siegel (report author), D.M. Cox, H. Goronkin, J. Mendel, H. Morishita, M.C. Roco
The afternoon of July 22 from 13:30 to 16:00 was spent at the Electrotechnical Laboratory (ETL) of the Agency of Industrial Science and Technology (AIST) of the Ministry of International Trade and Industry (MITI). It is more than 100 years old and is the largest national laboratory in Japan, with ~ 530 researchers and an annual budget of $100 million, according to a general introduction to ETL presented by its Director-General, Dr. Koichiro Tamura. Of this budget, ~ 15-20% is currently focused on various aspects of nanotechnology. The four major fields of research and development activities at ETL are (1) Electronics and Bioelectronics, (2) Energy Technology, (3) Information Technology, and (4) Standards and Measurement Technology.
The work in the Electronics and Bioelectronics area, in which most of the nanotechnology efforts reside, is carried out primarily in four divisions, which are themselves each comprised of several sections. These divisions, their constituent sections, and their respective leaders are as follows:
After an introduction to the ETL, our host, Dr. Tsunenori Sakamoto, Director of the Electron Devices Division, kindly provided answers to the questions posed by the WTEC panel prior to its visit. He said that his researchers are focusing on a single-electron device that can operate at room temperature ("smaller is better") using scanning tunneling microscopy (STM) and electron-beam fabrication technologies, but he indicated that they were not yet successful. ETL is seven years into its 10-year Quantum Functional Device (QFD) Project (1990-2000), having spent about $40 million so far, with $8-9 million per annum anticipated for the remainder of the project. According to Dr. Sakamoto, the proposals for the direction of ETL's work come "randomly" from industry, university, laboratory researchers, and MITI officials. His division expects a follow-on project on one-electron devices, and he also indicated that MITI has begun a new five-year project on fullerenes/nanotubes in Tsukuba at the National Materials Laboratory with funding of $20-30 million for five years. Collaborations between ETL and the U.S. National Institute of Standards and Technology exist in the areas of STM and liquid crystals.
Technical presentations and laboratory visits followed. The laboratory facilities at ETL are extensive and excellent. They are typical of a mature and well funded research establishment in that all the necessary equipment is available, but the excesses have been avoided of other newer laboratories the panel visited, where there sometimes seemed to be more new expensive equipment than people to use it effectively.
Dr. Sakamoto continued with a description of some research activities at ETL on nanotechnology. He described an STM nanooxidation process for creating a one-electron device showing quantum blockade behavior. The process consists of an STM tip with a water droplet between it and a 3 nm thick layer of Ti on an SiO2 layer on a Si substrate. TiOx is formed at the STM tip/H2O/Ti interface. ETL researchers are also doing this on stepped alpha-Al2O3 substrates. This technology has now flowed into other laboratories.
Dr. Masanori Komuro then described an electron-beam writer with a 3 nm diameter beam in ultrahigh vacuum - UHV (10-9 torr). Since the normal resolution of polymer resists (e.g., PMMA) with electron-beam lithography and a 50 keV electron gun is about 10-20 nm, higher resolution is needed. His staff report being able to do much better, yielding smaller features, with SiO2 films using electron beam lithography. A single-electron transistor, written by W dots or wires from WF6 using electron-assisted deposition, was reported to operate at 230 K.
Dr. Junji Itoh, standing in for Dr. Seigo Kanemaru (Senior Researcher in the Electron Devices Division), then reported on nanostructure activities in the area of vacuum microelectronics. Work was being carried out to create ultraminiature field-emitter tips (Mo, Si) for field emission displays. The tips have about 10 nm radii, can be created in two-dimensional arrays, and show increased emission levels. Because of problems with the stability of emission currents in conventional tips from reduced gas adsorption from the ambient atmosphere, development of MOSFET-structured emitter tips is being pursued, which will enable the combination of light emission and Si-based electronics on the same device structures.
Next, Dr. Hiroshi Yokoyama, Leader of the Molecular Physics Section, described ETL's Scanning Maxwell-stress Microscope (SMM), a new instrument that can look at nanoscale electrical characteristics (work function or charge distribution) as well as structure (topography) by detecting electric long range forces with about 1 mV sensitivity. The instrument is based on an STM or atomic force microscope (AFM), but by oscillating the probe (tip), it is possible to obtain additional information regarding dielectric constant, etc. (Yokoyama et al. 1994; Yokoyama and Inoue 1994). With the SMM, it is even possible to look at living cells under water. The instrument is in use at ETL in various experimental forms, but it is also now beginning to be commercialized by Seiko Instruments (in a price range of $500 thousand to $1 million) in a UHV version with variable temperature capabilities (70-500 K) and both SMM and AFM modes of operation. Future directions for the research work in this area will investigate semiconductor nanodevices under UHV conditions and problems in nanobiology under water. New functionalities for the SMM will be developed using higher frequencies to investigate band structure and the effects of doping, as well as optoelectrical investigations in combination with near-field optical microscopy (an effort funded by AST).
Finally, Dr. Hiroyuki Oyanagi described some work in the Physical Science Division on probing nanostructures with EXAFS. Dr. Oyanagi's group has a close relationship with a number of other groups worldwide. Its EXAFS studies are being carried out at an undulator beamline at the Photon Factory about ten miles from Tsukuba. They have been able to induce local melting by optical excitation and subsequent quenching-in of disordered regions in Se, and they are hoping to use this method for memory applications, if it can be done microscopically. Dr. Oyanagi also mentioned very briefly some work going on in ETL's Materials Science Division on nanostructured one-dimensionally modulated GaAs quantum well systems.
Yokoyama, H., T. Inoue, and J. Itoh. 1994. Appl. Phys. Lett. 65:3143
Yokoyama, H., and T. Inoue. 1994. Thin Solid Films 242:33.