Annual Activity Report 2004
著者
東北大学金属材料研究所
journal or
publication title
自己点検評価報告書「東北大学金属材料研究所の活
動」
year
2005
URL
http://hdl.handle.net/10097/56503
Preface
With a history of more than 89 years, the Institute for Materials Research (IMR) is committed to both basic and applied research and education in the field of metals and related materials. IMR has contributed to the development of academia, science and technology while educating many people who have become leaders in a wide range of roles in the society. In 1987, IMR was reorganized to its present form of a national collaborative research institute affiliated to Tohoku University. It has developed as a Center of Excellence for state-of-the-art research on metals and a wider range of other advanced materials. IMR has been visited by many researchers from Japan and other countries. With their participation, research projects involving collaboration with IMR’s individual research laboratories and the use of IMR’s facilities and equipment are actively progressing.
Innovative research on advanced new materials, which is IMR’s primary commitment, depends mainly on the creativity of individual researchers who have a distinctive originality. However, implementing large-scale projects in collaboration with individual researchers is becoming increasingly important. In line with this, IMR intends to actively participate in large-scale projects launched by Japan’s ministries and agencies according to the “Second Science and Technology Basic Plan” initiated in April 2001. The target of this plan is to promote the applications of basic research achievements for the society.
IMR understood the necessity of disseminating its accomplishments in the areas of research, education and social activities. An Office of Information and Public Relations headed by a deputy director has been established when Tohoku University was granted corporate status in April 2004. The new office includes a library, a public relations section, a review section and an integrated network operation section. After the reorganization of IMR in April 2004, this report has been prepared by the Review Office and completed by the review section headed by the chairperson of the Research and Planning Coordination Committee (called the Review Committee until 2001, the FY 2003 chairperson was Prof. Sadamichi Maekawa). The Office of Information and Public Relations was firstly headed by deputy director Shuji Hanada and then from April 2005 by deputy director Masayuki Hasegawa.
This report was developed by the Review Office which collected a large amount of data with the cooperation of all IMR members including the teaching, administrative and technical staff. Most of
the data on individual teaching staff are from the Tohoku University Information Database (operation started in December 2004) which was created and designed for various kinds of evaluations in the university. Within IMR, Prof. Hasegawa, the head of the Review Office, is responsible for editing this report and the research associate Ms. Utako Onose works for its practical business to keep an organic collaboration with the whole university evaluation system that started when the corporate status was granted.
By publishing this report on our activities relating to research, education and the social contributions, IMR intends to be accountable to tax payers, to receive evaluations from the standpoint of specialists and the general public reflecting the results on its future development, and to share its accomplishments with the society. This year’s report is especially meaningful since it includes details on the research and educational activities and social contributions that were performed in the first corporate year of IMR.
It would be my pleasure if this report is taken up, read and reviewed as basic literature to evaluate and criticize the IMR, which is indispensable for the future progress of IMR.
October 2005
Prof. Akihisa Inoue Director of IMR
Chapter 1: Mission and Future Visions
1. Introduction
In 1987 the Institute for Materials Research (IMR) was reorganized into the present form of a national collaborative research institute. Since then it has aimed at both “basic and applied materials science.” As our English name indicates, we are dealing not only with metals but also with materials in general. (The original Japanese name, a literal translation of which would be “Institute for Metallic Materials Research,” has not been changed.) Speaking of technical terms, in Japanese we can use different words to mean “materials” (e.g. zairyo, busshitsu, and sozai). Such a rich collection of terms is one demonstration that Japan is leading the research activities in materials science in the world and we are proud of this fact. In 1987, we established the Laboratory for Advanced Materials to create a framework for research on future applications of a variety of promising materials already developed by us. In 2002, we opened the International Frontier Center for Advanced Materials, which emphasizes fundamental research on materials science from an international viewpoint. As we have mentioned above, our mission is to contribute to the cultural development and people’s welfare by carrying out both basic and applied research in a wide range of materials such as metals, semiconductors, ceramics, organic materials, and composite materials, and to develop new materials that will be of great use in the highly-advanced technological society of the 21st century. To accomplish this mission, we have shifted our research policy from being mostly committed to the development with the greatest efficiency, to giving consideration to energy conservation, environmental protection, and the future aged society of Japan. Since Tohoku University was privatized in April 2004, the Institute has been converted into an affiliated institute of the University in the new system, and we are working towards further development of the Institute in order to incorporate the purposes and the vision of the privatization. Based on these circumstances, we have set out a number of basic objectives for the mid-term project in the first term (six years from 2004 to 2009) following the privatization.
Since its establishment, as a COE (Center of Excellence) of materials research, the Institute has been one of the leading materials research centers in the world and has invented many new materials. Our inventions have made a significant contribution to developing the infrastructure for the advanced industrial society of the 20th century. As an international COE of the science of various materials, mostly metallic ones, we have extensively made research in materials science and its applications. The basic objective of our institute for the 21st century is to contribute to the continuous development of society and the prosperity of humankind by developing new materials, incubating excellent materials researchers, and promoting materials science which will serve as
the infrastructure for the front line of science and engineering, including environmental protection, energy saving, bionics, information and communications, and advanced safe space technology.
Currently the Institute has a total floor area of 34,320m2, with about 600 people, including staff members, guest researchers and graduate students. It is the largest institute affiliated to a university in Japan. The number of research papers published is about 700 annually. Tohoku University was ranked as the first one in the number of citations in materials science papers published between 1991 and 2001 according to the classification of the research institutes throughout the world (Science Watch, vol.12, No.4, 2001). The analysis of the citations tells that the Institute has made the most contribution to materials science. We are very open to foreign countries; about 65 researchers from abroad are working with us. There are also a number of short- and long-term visitors. Every month many lectures are given by researchers from Japan and abroad. The Institute also serves as a hub for international cross-disciplinary exchanges and joint research.
The following sections provide a summary of our activities, define our research objectives and future visions, and describe our effort for improving the research environment.
2. Future Visions
The Institute was started by the chief researcher, Professor Kotaro Honda, in 1916. The Institute has always been the center of materials research in Japan, having accomplished a great number of achievements and trained excellent researchers. It was initially established on a request from the government to serve as a foundation for the steel industry. However, we have been always shouldering responsibilities to meet the needs of the times because materials research provides the foundation of science and technology. For Japan to remain on the front line of science and technology in the 21st century, a constant leap in materials science and rapid progress from fundamental research to applications are required. Taking advantage of the rich collection of intellectual properties on materials science based on our history and achievements, we are determined to serve as the center of fundamental materials research in the 21st century.
Since its foundation, the Institute has always been ahead of the times in its belief that materials research is the foundation of science and technology. Steel was the fundamental material of domestic industry in the time of Professor Kotaro Honda. Now semiconductors, especially silicon, which is now often referred to as the chief material of all industries, are indispensable to current advanced electronics. There is an urgent need for the development of
fundamental materials for the next generation of semiconductors. For development in such a new field, new research environment and systems are required. As the center of materials science, our mission is to contribute to the development of human culture by carrying out fundamental and applied research on a wide variety of materials and creating new useful materials. With this mission in mind, we are performing close collaboration of research using unique experimental equipment and corresponding theories and simulations, which befits our policy as an advanced comprehensive research institute for the development of new materials from the atomic level, exploration of useful characteristics and phenomena, and resulting applications.
As we stated earlier, materials science forms the foundation of science and technology. It requires cross-disciplinary research without being bound by traditional differences among academic research fields. The reason that we converted ourselves into a national collaborative research institution and changed our name to the “Institute for Materials Research” was to enable our research activities from a wider variety of these perspectives.
The Institute is located in Sendai City, in the northern part of Honshu (the central island of Japan). It is surrounded by research institutes in various fields including life sciences, information and communication technology, scientific instrumentation and measurement, hybrid (organic and inorganic) materials science, and fluid science in Tohoku University. We expect that close collaboration with these institutes will create an ideal environment for carrying out materials research, developing the science and technology of the 21st century, and educating promising researchers. We are also leading programs for cooperation among the research institutes in the university.
A new material often creates a new industrial foundation. Therefore it is very necessary to set up a system for rapidly turning the fruits of fundamental research into industrial applications. Some independent administrative institutions in Japan such as the National Institute of Materials Science (NIMS) and the National Institute of Advanced Industrial Science and Technology (AIST) have experience in project research in industrial applications of new materials. Developing a system in cooperation with these institutions for bringing fundamental research to the industry-academia
-government collaborative research projects at the national level will enable a faster response to social needs. Furthermore, exchanges of researchers and students at NIMS are breaking down the traditional walls between universities and research institutions and will make a meaningful contribution to the development of true cross-disciplinary research and education.
3. System and Method of Operation
The Institute comprises of 27 research laboratories, 3 laboratories of visiting professors and 4 attached research centers which directly promote research and education, together with various support organizations such as technical service division and administrative office, which enable smooth and effective research and educational activities. There were also various committees, including the executive committee, for managing discussions at faculty meetings and for supporting the director. However, the excessive number of committees and resulting inefficiencies posed a serious squeeze on research activities. To resolve this problem, we implemented a variety of reforms towards a more efficient and simplified operation of management.
Following the privatization of the national universities in April 2004, we declared the following mid-term objectives and programs for executing a ground-up reform of the management system: - Clarifying the leadership roles and responsibility of the director.
- Establishing a transparent decision-making organization.
- Efficient operations for enabling faculty members to concentrate on their research as much as possible.
We took the following steps to improve the management operations stated above:
- Appointing the leader of the Institute, the director, and assigning two deputy directors (one for research and education, and the other for management and operations).
- Setting up an executive committee comprising the director, deputy directors, research-planning office manager, information and public relations office manager, strategy office manager, industrial relations office manager, two faculty meeting members (professors), and the head of administrative office manager.
- Holding faculty meetings with professors and associate professors for discussing research and education, and faculty staffing.
- Setting up an external evaluation committee for evaluating the overall activities of the Institute. - Setting up an external advisory board of materials science specialists from home and abroad (more than half of the members are overseas researchers) to provide advice on our 10- and 20-year visions, and the directions of research.
In addition:
- Setting up a committee (under the direct supervision of the director) and an office for controlling and ensuring safety and health.
Under the executive committee:
- Setting up an office for research planning to discuss research plans, mid-term objectives, and projects. This office determines the number of faculty members, selects visiting faculty members,
overseas researchers, part-time researchers, plans the work rules, handles budget requests and distribution, and investigates tasks concerning the land and buildings.
- Setting up an office of information and public relations for announcing the results of research and for gathering information on researchers. This office also helps the director with his inspection and evaluation of various activities including the operations of the library and computer network, public relations for the Institute as a whole, research and education of the Institute and its faculty members. It also reviews and discusses summer seminars and lectures. - Setting up an office of industrial relations to promote the industrialization of the outcome of the
research carried out in the Institute. This office encourages the researchers to obtain patents for useful materials. The office also supports collaborative research with private companies and activities for reinforcing industry-academia-government cooperation.
- As the front runner in materials science research, setting up an office of strategy for discussing the promotion of advanced research and researcher training, and the management and operations of the Institute in the short and the long terms.
- Maintaining the conventional small laboratory system to encourage the birth of new research from bottom-up efforts in each laboratory, help the research to bloom and bear fruit. In general, each laboratory consists of a professor, an associate professor, and research associates. However, the configuration and numbers are not fixed in order to enable responsive and flexible staffing. The director manages the vacant posts that arise due to personnel changes and retirements, following the decisions of the executive committee to allow flexibility in personnel distribution. - The professor of each laboratory is selected from candidates by the laboratory research
characterization committee and the selection committee organized in the faculty meeting based on the mid-term objectives and projects planned by the executive committee, and finally adopted at the faculty meeting.
- Exploring new research fields by adopting a visiting professor system to overcome the limitations on the research fields already covered by the current members of the institute. - Making efforts to prepare and enrich the facilities for shared use, and to upgrade equipment in
order to further promote collaboration with internal and external researchers. The general principles on the collaborative research programs are discussed by the users committee, which comprises of directors from the three graduate schools for science and engineering, three research institutes and one research center at Tohoku University which are closely related to our Institute, and further internal and external specialists appointed by the director of the Institute. The Committee members include those from industry circles as well as academia to obtain advices and suggestions from them. The specifics of the collaborative research are discussed by the research laboratory divisions in each department and the committee in each
attached center. The advisory committee for the collaborative research is set up to discuss the basics of the shared use of the entire Institute and to undertake the coordination between the committees.
4. Recruiting and Faculty Staffing
As of April 1, 2004, the Institute staff comprises of 25 professors, 33 associate professors, 2 assistant professors, and 70 research associates. In the attached centers, （ⅰ）five associate professors and three associates work for the International Research Center for Nuclear Materials Science, （ⅱ）one professor, four associate professors, and four research associates for the Laboratory for Advanced Materials ( renamed as the Advanced Research Center of Metallic Glasses in April, 2005), (ⅲ) one professor, two associate professors, and two research associates for the High Field Laboratory for Superconducting Materials, and (ⅳ)two professors and one research associate for the International Frontier Center for Advanced Materials.
We also have several visiting researchers. Three Japanese researchers are located in the Research Department, one Japanese and one foreign researcher in the Advanced Research Center of Metallic Glasses and three foreign researchers in the International Frontier Center for Advanced Materials.
The number of research laboratories other than visiting researcher sections is 27. In general, each laboratory comprises of one professor, one associate professor, and two research associates. However, different configurations are also possible.
Professors are recruited from applications open to the public. If a vacant position arises or is scheduled to arise, a faculty meeting decides the characteristics of the laboratory concerned, and then sets up a selection committee consisting of four professors. The result of the selection is reported to the faculty meeting to obtain its approval. In many cases, before this, an extended selection committee is held in order to have comments and suggestion from other professors before a final decision is made. Associate professors, assistant professors, and research associates are also recruited from applications open to the public as a general rule. However, in some cases the professor of each laboratory can recruit his/her research staff without the open-application procedure when it is not necessary. To select associate professors and lecturers, the faculty meeting sets up a selection committee of three professors and one associate professor. The result of the selection is reported to the faculty meeting. Recruiting research associates does not require a selection committee. The professor of each laboratory directly suggests candidates. In either case, the faculty meeting makes the final decision by taking a vote.
in each laboratory is larger than that in other departments and universities. If all members of each laboratory concentrate their research on a single research area, they can execute a fairly large project. However, if the professor retires or leaves his/her laboratory without releasing all members, his/ her successor is required to work with the associate professors and research associates assigned by the former professor. However, it may happen that the new professor cannot have joint work on the research project with the remaining staff, in which case the advantages of a large-scale division cannot be fully exploited. To prevent such stagnation or decline in research activities due to the change of professors, all of the professors are required to make efforts to transfer their staff in advance of leaving or being retired. In general, a professor cannot recruit new staff if he/she is scheduled to retire or leave in less than three years. However, to maintain research activities, it is possible to hire research associates for a limited period until the new professor takes up his/her position.
5. Future Planning
As we have stated above, with the privatization of the national universities in April 2004, our Institute restarted as an institute affiliated to Tohoku University. Society is expecting universities to have competitiveness on an international scale with individuality, independence and autonomy. Our mission is to show a definite direction as a world-wide leading center of materials science in the 21st century.
With those demands in mind, we issued a questionnaire to all staff regarding the future visions of the Institute. The results are summarized as follows:
1) An institute that executes the materials research from the fundamentals to the applications. 2) Promoting cross-disciplinary research by breaking down the barriers between science and
engineering.
3) Maintaining a balance between “uniqueness” and “diversity” in research activities.
4) Recognizing the importance of research for solving “social issues,” such as energy, environment, and the future aged society.
5) Developing as a center of materials research in the world. 6) Discovering new research fields
7) Reinforcing incubation of young researchers.
Since we work for an institute with the principal objective of “creating new materials” with the awareness that “materials offer the basis for all science and technology ”, we should continue our research activities with a sense of balance, without any bias towards certain materials. We wish to develop core researchers who will stand at the front line of the Institute while maintaining a flexible environment which inspires researchers. We will also support research that makes full
use of our facilities and encourage scientific and engineering to researchers to work together. Since its establishment, the Institute has always worked on materials which are closely related to people’s daily lives. We will continue exploring metallic and related materials and maintain a realistic attitude to materials research studies. Our mid-term objectives and projects define the following research fields:
1) Nano-structured/special structured metallic materials 2) Materials for environmental protection and energy saving 3) Materials for use in electronics
4) Materials for use in nuclear energy
Our mid-term projects are expected to yield great results which will take the lead in society and academia in each field. We will select a number of these and define a top-down long-term strategy for the future.
1. Organization of Institute for Materials Research
Theory of Solid State Physics Crystal Physics
Magnetism
Materials Property Surface and Interface Research
Division Low Temperature Physics
Low Temperature Condensed State Physics Neutron and γ-ray Spectroscopy
on Condensed Matters
Materials Design and Property Control* Physics of Crystal Defects
High Purity Metallic Materials
Materials Design by Computer Simulation Materials Design Irradiation Effects in Nuclear
Division and Their Related Materials Nuclear Materials Science Nuclear Materials Engineering
Research Physics of Electronic Materials
Laboratories Advanced Electronic Materials
Materials Design* Nano-Metallurgy
for High Temperature Metals* Chemical Physics
of Non-Crystalline Materials Surface Materials Chemistry Materials Development Superstructured Thin Film Chemistry Division Non-Equilibrium Materials
Magnetic Materials Crystal Chemistry
High-Temperature Materials Science Multi-Functional Materials Science Deformation Processing
Radiochemistry of Metals Deputy and Characterization Structural Science
Director Division of Non-Stoichiometric Compounds Analytical Science
Director Materials Processing and Characterization
Deputy Director
Research Centers
High Field Laboratory for Superconducting Materials International Frontier Center for Advanced Materials
Office of Security and Health Office of Research Planning
Office of Information and Public Relations Office of Strategy
Office of Industrial Relations Analytical Research Core
for Advanced Materials Instrument Development Core
Center for Computational Materials Science Technical Services Division
Administrative Office
(*Laboratory of Visiting Professor) Laboratory for Advanced Materials
Materials Processing
Chapter 2 Organization
2．Organizing Committees
Board of Directors
External Evaluation Committee
External Advisory Board
Faculty Meeting Office of Research Planning Director
Office of Information and Public Relations Executive Committee
Deputy Office of Strategy
Director
Office of Industrial Relations Committee
for Safety and Health
Division of Research Laboratories
International Research Center Users Committee for Nuclear Materials Science
Advisory Committee Laboratory for Advanced Materials for Collaborative
Research
High Field Laboratory for Superconducting Materials International Frontier Center for Advanced Materials Office of Safety and Health
1. Situation of Research Budget
【
Regular Budget 】
【Grant-in-Aid （A)】
【Grant-in-Aid （B)】
Chapter 3 Budget
million yen million yen million yen 2,127 2,095 2,043 2,163 2,257 2,541 2,275 3,086 1,836 2,284 0 1,000 2,000 3,000 4,000 5,000 6,000 2004FY 2003FY 2002FY 2001FY 2000FY Personnel non Personnel 124 144 73 83 496 531 549 429 401 176 81 82 120 121 0 100 200 300 400 500 600 700 800 2004FY 2003FY 2002FY 2001FY 2000FYFrom Private Insustries From Private Insustries
From Ministry of Education, Culture, Sports, Science and Technology
528 527 441 407 442 0 100 200 300 400 500 600 2004FY 2003FY 2002FY 2001FY 2000FY
2. Grant-in-Aid for Scientific Research : Applied and Approved Proposals
No Yen (× 1000) Yen (× 1000) Yen (× 1000)
1 320,818 267,950 294,600 1 100,000 87,000 87,000 1 92,000 87,000 87,000 2 15,000 13,100 10,300 2 20,812 13,100 10,300 11 75,030 49,660 53,391 8 58,300 63,000 43,200 4 180,900 199,246 114,200 2 98,300 115,500 61,700 11 174,993 211,450 209,010 6 64,900 64,100 59,166 27 174,438 210,223 259,261 14 38,000 70,200 107,900 21 59,742 59,189 56,562 7 9,300 15,300 21,800 35 109,203 100,880 126,139 8 17,400 10,400 10,400 17 380,911 166,312 159,315 1 18,600 55,800 99,900 28 62,610 67,846 65,693 14 16,500 23,300 22,200 13 15,100 11,800 12,000 13 13,900 10,700 10,400 8,500 4,446 8,500 4,446 171 1,668,745 1,453,156 1,451,917 76 448,012 536,900 538,412 1 1 178 96 11 11 31 17 42 8 10 8 28 16 24 13 5 4 10 6 2 2 12 9 1 1 167 79 10 10 30 16 41 8 11 5 24 11 25 11 6 4 11 4 1 1 5 7
Applied Proposal Approved Proposals
1 1 1 1 1 2004FY No 1 No 2003FY Grant-in-Aid for JSPS Fellows Other
Grant-in-Aid for Special Purposes Grant-in-Aid for Publication of Scientific
Research Results
Sum
Research Item 2002FY Grant-in-Aid for Specially
Promoted Research Grant-in-Aid for Creative
Scientific Research Grant-in-Aid for Scientific
Research on Priority Areas (1)
Grant-in-Aid for Scientific Research on Priority
Areas (2)
Grant-in-Aid for Exploratory Research Grant-in-Aid for Young
Scientists （Ａ） Grant-in-Aid for Young
Scientists （Ｂ） Grant-in-Aid for Scientific
Research （Ｓ） Grant-in-Aid for Scientific
Research （Ａ） Grant-in-Aid for Scientific
Research （Ｂ） Grant-in-Aid for Scientific
3．Projects with Big Budgets
( x billion yen)
Ministry of Education, Culture, Sports, Science and Technology
1999-2004 FY Prof. Sadamichi MAEKAWA 680
1999-2005 FY Prof. Masashi KAWASAKI 290
2000-2004 FY Prof. Akihisa INOUE
Prof. Eiichiro MATSUBARA 200
2000-2005 FY Prof. Akihisa INOUE 130
2002-2006 FY Prof. Akihisa INOUE 2,200
2002-2006 FY Prof. Akihisa INOUE
Prof. Kenji HIRAGA 570
2003-2007 FY Prof. Sadamichi MAEKAWA 100
2003-2007 FY Prof. Akihisa INOUE 1,640
2003-2007 FY Prof. Yoshiyuki KAWAZOE 150
Radioactive Waste Management Funding and Research Center
2000-2005 FY Prof. Masayuki HASEGAWA 320
The Japan Science and Technology Agency (JST)
2001-2006 FY Prof. Yoshihiro IWASA 320
( x billion yen)
The Japan Society for the Promotion of Science (JSPS)
2002-2006 FY Prof. Masashi KAWASAKI 440
The New Energy and Industrial Technology Development Organization （NEDO）
2001-2005 FY Prof. Akihisa INOUE 2,800
2001-2005 FY Prof. Akihisa INOUE 6,700
2002-2004 FY Prof. Masashi KAWASAKI 70
2002-2006 FY Prof. Akihisa INOUE 3,600
Name Date Change Status
Knichi FUKUMOTO 2004.04.01 transfer to Fukui Univ. (Research Associate)
Wei ZHANG 2004.04.01 employment Associate Professor
Jing-ZHI YU 2004.04.01 employment Associate Professor
Masahiko HATAKEYAMA・ 2004.04.01 employment Research Associate
Takahiro HATANO 2004.04.01 employment Research Associate
Baolong SHEN 2004.04.01 employment Research Associate
Shinji KOH 2004.04.01 transfer from The Uniｖ. ofTokyo Research Associate
Minseok-SUNG 2004.04.01 employment Research Associate
Hiroyuki NOJIRI 2004.05.01 employment Professor
Yoshitaro NOSE 2004.06.01 employment Research Associate
Tokujiro YAMAMOTO 2004.06.01 employment Research Associate
Hidetoshi MIYAZAKI 2004.06.30 resignation (Research Associate)
Yukie KONNO 2004.07.01 employment (Techanisian)
CHOI Kwang Yong 2004.08.01 employment Research Associate
Yugo OSHIMA 2004.08.01 employment Research Associate
Tadaaki NAGAO 2004.08.31 resignation (Associate Professor)
Minseok-SUNG 2004.09.30 resignation (Research Associate)
Takaya AKASHI 2004.09.30 resignation (Research Associate)
Yasunori FUJIKAWA 2004.10.01 promotion Associate Professor
Rong TU 2004.11.01 employment Research Associate
Tomoteru FUKUMURA 2004.12.01 promotion Lecturer
Kehui Wu 2005.01.31 resignation (Research Associate)
Takashi MATUOKA 2005.02.01 employment Professor
Kazumasa TOGANO 2005.03.31 retirement (Professor)
Petre BADICA 2005.03.31 resignation (Research Associate)
Chapter4 Personnel Change
(2004.4.1～2005.3.31)Chapter 1 Research Activities and Future Plans
Theory of Solid State Physics
Prof.Sadamichi Maekawa
(1997.4~ )【Staff Members】
Prof. Sadamichi Maekawa, Assoc. Prof. Takami Tohyama, Res. Assoc. Tomio Koyama,
Res. Assoc. Saburo Takahashi, Res. Assoc. Wataru Koshibae〈Researcher : 4 / Supporting Staff : 3〉 【Research Activities】
In this group, the electronic states in transition metal oxides are theoretically studied. Transition metal oxides exhibit novel properties such as high temperature superconductivity and metal-insulator transition based on strong electron correlation and, thus, are important targets in condensed matter physics. They also attract attention as future electronic materials.
In 2004, the electronic states of Mott insulating states and doped ones in Cu-oxide (Ref.1, 2, 3 ), Co-oxides (Ref.4 ) and Mn-oxides (Ref.5 ) were theoretically studied:
(1) The nature of the spin-charge separation in one-dimensional correlated electrons was clarified, and was shown to be the key for the giant non-linear opto-electronic responses. The idea for the development of the non-linear opto-electronic materials was proposed.
(2) The interaction among the internal degrees of freedom of electrons (spin, charge, orbital) in strongly correlated electrons, the competition of their orders, the elementary excitations and the observation methods were studied. In particular, the methods that may be used in the synchrotron radiation facilities were proposed.
(3) Cobaltates with triangular lattice structure attract attentions as thermo-electric materials and novel superconductors. It was shown that in the cobaltates, the electronic lattice is different from that of the crystal and is the Kagome. This is because the orbital degeneracy causes the different symmetry to the electrons from the crystal.
(4) The textbook entitled "Physics of Transition Metal Oxides" was prepared for several years and has finally been published from Springer (Germany) in June 2004 (Ref.1 ).
1. Maekawa S., Tohyama T., Barnes S.E., Ishihara S., Koshibae W., Khaliullin G. Physics of Transition Metal Oxides
Springer Series in Solid-State Sciences, Vol. 144 (2004), ISBN: 3-540-21293-0 2. Mori M., Tohyama T., Maekawa S., Riera J. A.
Friedel oscillations in a two-band Hubbard model for CuO chains. Phys. Rev. B 69 (2004), 014513
3. Onodera H., Tohyama T., Maekawa S.
insulators.
Phys. Rev. B 69 (2004), 245117
4. Khaliullin G., Koshibae W., Maekawa S.
Low Energy Electronic States and Triplet Pairing in Layered Cobaltate. Phys. Rev. Lett. 93 (2004),176401
5. Ishii K., Inami T., Ohwada K., Kuzushita K., Mizuki , J., Murakami Y., Ishihara S., Endoh Y., Maekawa S., Hirota K., Moritomo Y.
Resonant inelastic x-ray scattering study of the hole-doped manganites La1-xSrxMnO3 (x = 0.2, 0.4).
Phys. Rev. B 70 (2004), 224437 【Plan】
Most of transition metal oxides are the so-called strongly correlated electron systems, since the Coulomb interaction between electrons is strong. In the oxides, electrons stay in the ionic cores for long time and, thus, the internal degrees of freedom of electrons (spin, charge, orbital) behave almost independently. The degrees exhibit the ordered states that compete with each other. As a result, a variety of quantum phenomena occur. The same physics is applied to organic molecular materials and bio-materials as well. Because of the competition among the degrees, a small change of spin (magnetism) and/ or orbital (spatial behavior of electron cloud) causes a giant response of charge (electrical transport). The reverse response occurs as well. Since these quantum phenomena are due to the many-body effects of electrons, the band calculation based on the local density approximation and the mean-field approximation calculation do not always catch the fundamental physics of the phenomena.
On the other hand, numerical simulation based on the microscopic model works well to solve the physics. Our research group has been developing the numerical simulation methods for the strongly correlated electron systems. The methods are applied to a variety of novel quantum phenomena in the correlated electron systems. The group reveals the physics of the phenomena and proposes the idea of developing materials for the future electronics.
Crystal Physics
Prof. Kazuo Nakajima（1998.10～）【Staff Members】
Prof. Kazuo Nakajima, Assoc. Prof. Noritaka Usami, Lecturer Gen Sazaki,
Res. Assoc. Kozo Fujiwara, Res. Assoc. Yoshitaro Nose〈Researcher : 2 / Supporting Staff : 2〉 【Research Activities】
1 ) Studies on the crystals for solar cells with high conversion efficiency
We have fabricated multicrystalline SiGe solar cells with microscopic compositional distribution and proved, for the first time, that SiGe bulk multicrystals with an average Ge composition of 5% gave 1.3 times higher conversion efficiency than Si bulk multicrystals did. We studied the cause of this high efficiency, and concluded that Ge-rich regions in the crystals refracted light and thus elongated effective optical pass increased the absorption coefficient of the cells.
To elucidate key parameters necessary for the increase in the quality of Si bulk multicrystals, we developed an in-situ observation system available up to 1500°C, and succeeded in observing melt growth process of Si crystals in-situ for the first time. Using this system, we found that a dendrite growth mechanism of Si crystals could be applied to control the crystallographic orientations of Si bulk multicrystals. Our new findings in the growth of high quality Si bulk multicrystals are highly evaluated by NEDO and other companies as core technologies necessary for future studies on solar cells.
We found that Si crystal wafers with various three-dimensional shapes can be prepared using plastic deformation under certain ranges of temperature, thickness and pressing overweight. Since these Si crystal wafers with various shapes have enough quality for preparing solar cells and X-ray condensing lenses, this process can be a promising technique to prepare a new high-efficiency solar cell system with the concave Si crystal mirror solar cells. The crystal lenses are also very useful for preparation three-dimensional X-ray crystal lens.
2 ) Growth of multi-component bulk substrate crystals with uniform composition and studies on hetero-epitaxial structure with controlled strain
We found that a <110> direction is a preferential orientation for the growth of InGaAs crystals. We used a (110) face of a GaAs seed crystal and succeeded in growing a InGaAs single crystal even when InAs composition was close to 25%. This growth technique gave big progress in the growth of InGaAs single bulk crystal.
3 ) Studies on the crystal growth of organic materials
We developed a novel in-situ observation technique by which movement of individual protein molecules in the vicinity of a solution-crystal interface can be tracked real-time. This technique can be a promising tool for studying mechanisms of protein crystallization.
1. Pan W., Fujiwara K., Usami N., Ujihara T., Nakajima K., and Shimokawa R.
Ge composition dependence of properties of solar cells based on multicrystalline SiGe with microscopic compositional distribution
2. Fujiwara K., Obinata Y., Ujihara T., Usami N., Sazaki G., and Nakajima K. Grain growth behaviors of polycrystalline silicon during melt growth processes J. Cryst. Growth, 266 (2004), 441-448.
3. Nakajima K., Fujiwara K., and Pan W.
Wave-shaped Si crystal wafers obtained by plastic deformation and preparation of their solar cells
Appl. Phys. Lett., 85 (2004), 5896-5898.
4. Azuma Y., Nishijima Y., Nakajima K., Usami N., Fujiwara K., and Ujihrara T.
Successful growth of an InxGa1-xAs (x>0.18) single bulk crystal directly on a GaAs seed crystal with preferential orientation
Jpn. J. Appl. Phys. 43 (2004),L907-L909.
5. Sazaki G., Matsui T., Tsukamoto K., Usami N., Ujihara T., Fujiwara K., and Nakajima K. In-situ observation of elementary growth steps on the surface of protein crystals by laser confocal microscopy
J. Cryst. Growth, 262 (2004), 536-542 【Plan】
Our main areas of research include (but are not limited to)
(1) Development of novel photovoltaic materials for high-efficiency solar cells
We attempt to develop a novel crystal growth technique to realize multicrystalline Si ingots with artificially controlled orientations, grain boundary characters, and grain sizes, which are believed to surpass single-crystalline Si in terms of crystal quality. This pioneering study will lead the research and development of practical solar cells. The mechanism of the improved conversion efficiency of the solar cells based on SiGe multicrystals with microscopic compositional distribution will be clarified at a fundamental level, which will play an important role to industrialize thin film crystal solar cells for the next generation. Furthermore, record conversion efficiency will be pursued based on a novel solar cell system using Si concave mirror solar cells.
(2) Development of multicomponent semiconductor bulk crystals with uniform composition and their application to novel semiconductor substrates
Novel crystal growth technique to realize multicomponent semiconductor bulk crystals with uniform composition will be established to widen the choice of lattice-constants and band gaps of semiconductor substrates for strain-controlled epitaxial growth of heterostructures, which leads to the development of new functional materials. The validity of this concept will be demonstrated by a prototype high-mobility devices based on strain-controlled SiGe heterostructures grown on homemade SiGe substrates.
(3) Fundamental studies on epitaxial growth mechanisms of organic semiconductor thin film crystals
We will clarify the key mechanisms to control the alignment of organic molecules, which will be utilized to develop a novel epitaxial growth technique to realize "single-crystalline" organic semicondoctor thin films.
Magnetism
Prof.Hiroyuki Nojiri
(2004.4～ )【Staff Members】
Prof. Hiroyuki Nojiri, Res. Assoc. Iwao Mogi, Res. Assoc. Yugo Oshima, Res. Assoc. Kwang-Yong Choi
【Research Activities】
Major research subjects of our group are study of magnetism under very strong magnetic fields and the material processing by using high magnetic fields.
In magnetism, the research has been focused on the search of new nano-magnets and on investigation of the quantum mechanical properties. Main results are as follows. (1) Discovery of spin tube and spin prism and the examination of the magnetic properties (Ref.1 ), (2) Study of quantum tunneling and quantum hysteresis in spin triangles, which appears for spin chirality (Ref.2 ), (3) Investigation of spin polyhedrons, especially the size effect and the ground state (Ref.3 ), (4) Study of spin parity effect in single molecular magnets by using high frequency ESR.
These researches have been performed as the domestic and international collaborations with more than 10 groups. It has been established that time-dependent magnetic fields are a unique and useful tool to manipulate nano-spin systems quantum mechanically.
Magnetoelectropolymerization of conducting polymers has been studied as applications of magnetic fields to materials processing. We have found that magnetoelectropolymerized polyaniline films exhibit ability of enantioselective recognition for chiral molecules (Ref.4 ).
A compact pulsed field generator has been developed for high magnetic field X-ray diffraction experiments. The world record of 33 T has been achieved at SPring8 facility. (Ref.5 )
1. J. Schnack, H. Nojiri, P. K Gerler, Geooerey J. T. Cooper, Leroy Cronin
Magnetic characterization of the frustrated three-leg ladder compound [(CuCl2tachH)3Cl]Cl2 Phys. Rev. B 70 (2004)174420(5 pages).
2. T. Yamase, E. Ishikawa, K. Fukaya, H. Nojiri, T. Taniguchi, T. Atake
Spin-Frustrated (VO3)6+-Triangle-Sandwitching Octadecatungstates as a New Class of Molecular Magnets
Inorg. Chem. 43 (2004) 8150-8157.
3. C. Schroder, H. Nojiri, J. Schnack, P. Hage, M. Luban, P. Koegrler
Competing Spin Phases in Geometrically Frustrated Magnetic Molecules Phys. Rev. Lett. 94 (2005) 017205(4 pages).
4. I. Mogi and K. Watanabe
Chirality of Magnetoelectropolymerized Polyaniline Electrodes Jpn. J. Appl. Phys., 44 (2005) L199-L201.
5. T. Inami, K. Ohwada, Y. H. Matsuda, Y. Ueda, H. Nojiri, Y. Murakami, T. Arima, H. Ohta, W. Zhang, K. Yoshimura
X-ray Diffraction Experiments under Pulsed Magnetic Fields above 30 T Nucl. Instrum. and Methods (2005) to be published.
【Plan】
The aims of our group are study of magnetism under very strong magnetic fields and the material processing by using high magnetic fields. Toward these purposes, following plans have been made.
(1) Study of nano-scale magnet
It is important to find out nano-magnets with new topology. For example, spin tube, spin prism and spin polyhedron are very important When antiferromagnetic interactions are dominating in those systems, various metastable states are expected to appear because of the frustration and of the degeneracy of energy levels. It is interesting to study the quantum dynamics of such systems, especially the quantum tunneling of magnetization.
(2) Control of quantum dynamics
The most important but most difficult breakthrough in nano-magnetism will be the control of decoherence. A time depending magnetic field can be a unique tool for the quantum mechanical manipulation of spins. New methods should be developed to solve the "decoherence problem". (3) Material processing by using high magnetic fields
It is important to search a new material processing process by using magnetic fields, such as magnetoelectropolymerization in high magnetic fields. New functions will be attached by using such synthetic process.
(4) Development of high field X-ray diffraction system
The combination of X-ray and magnetic field will be a powerful tool to investigate various phase transitions. For this purpose, a compact pulsed magnetic field generator should be developed. Intense research and development efforts should be made to combine the pulsed magnetic fields and the synchrotron X-ray.
(5) Wide Research collaboration in nano-magnetism
It is important to establish the wide collaboration among different research groups in the field of nano-magnetism. The magnetism division of IMR will be one of the centers in this research field.
Surface and Interface Research
Prof.Toshio Sakurai
(1989.10~ )【Staff Members】
Prof. Toshio Sakurai, Assoc. Prof. Yasunori Fujikawa, Res. Assoc. Jerzy T. Sadowski, Res. Assoc. Yukiko Yamada-Takamura〈Researcher : 2 / Supporting Staff : 1〉
【Research Activities & Plan】
In academic year 2004, Dr. Nagao's group continued the STM/LEEM investigation of the thin film Bi growth on the Si (111)-7×7 surface to elucidate the mechanism of coverage-dependent phase transition of the Bi ultra-thin film. We concluded with the help of theory group in NIMS that the Bi film has a unique new phase, which stays stable up to the film thickness of 4 monolayers. The bonding configuration of this phase is similar to black phosphorus which belongs to the same elemental group as Bi, but has been never observed in bulk Bi. (Ref.1 ) We wishfully hope that this new allotrope of Bi may possibly be accompanied with exotic electronic properties, realizing unique Bi properties. We plan to investigate it in the coming year, although Dr. Nagao left our group in September 2004 to take a position at NIMS, Tsukuba.
The main thrust of our group for last couple of years is Ge (105)/Si project mainly performed by Dr. Fujikawa and his students. Realizing its rather complicated nature of the surface structure due to large charge transfer, they used high-performance atomic force microscopy (AFM) to nail down the details of atomic structure of Ge (105)/Si in collaboration with Dr. Hasegawa's group at ISSP, University of Tokyo. (Ref. 2 ). They found that the obtained AFM images documented the exact positions of the dangling bonds on the surface with the resolution even higher than the best STM images currently available. Furthermore, using the Kelvin force microscopy together with the AFM, an atomically-resolved potential map was successfully resolved on the surface, which rendered additional support to the structure model we proposed. To our best knowledge, this is the first atomically resolved potential mapping obtained using this unique technique. These results nicely exemplify the powerfulness of AFM in surface structure. This research was extended to further investigate hydrogen adsorption and they have found that the surface strain on this surface is controllable by the hydrogen adsorption. (PRL 94, 086105 (2005).) This work implies the possibility of strain control of Ge quantum dots on Si through adsorption. Use of "surface strain" as a controllable parameter in surface engineering will be our major area of research for the coming years. For instance, we plan to investigate in what degree we can modify the strain in the Ge films and nanostructures by adsorption in order to control mechanical and electronic properties of the Ge/Si system.
Highly challenging "growth of GaN on Si" was attempted by Dr. Yamada-Takamura's group using the UHV molecular beam epitaxy (MBE)-SPM system. GaN is grown on Si (111) by radio-frequency plasma-assisted MBE, and the growth front is studied using reflection high-energy electron diffraction (RHEED) and STM. By successfully documenting the optimum nucleation/growth conditions, well-defined surface reconstructions, i. e. GaN-(000-1)-3×3, 6×6, and c(6×12), are observed by STM after the additional Ga deposition at ambient., indicating the uniform N-polarity of the grown film. They have concluded that the initial GaN nucleation under N-rich conditions is crucial to grow mono-polar uniform GaN films on the Si substrate (APL 87,
032110(2005)). We currently extend this GaN/Si system research to include ZrB2 buffer layer for better GaN film growth. We also plan to study diamond surfaces by UHV non-contact-AFM. Dr. Wu worked successfully to document the two dimensional nature of alkali metal adsorbate on the Si (111)-7×7 surface at low coverage and formation of magic cluster upon the critical coverage of 4 atoms/unit cell.. This work was further augmented by low-temperature STM study to control the movements of alkali-metal atoms on the surface. These results were in complete agreement with the theoretical potential mapping and computer simulation of STM data by Kawazoe-Lab. (Ref. 3 ) Dr. Wu left our group to take up a professorship at Institute of Physics, Chinese Academy of Sciences, Beijing in January 2005.
Halogen (Cl, F) etching of the GaN(000+1) surface is being continuously studied in connection to its technological importance in device fabrication process by Dr. Fujikawa's group. This work is part of S. Kuwano's Ph.D. thesis research. They found, among others, that the Ga-rich condition is essential to efficient etching of the GaN surface using chlorine. (Ref. 4 )
In LEEM/STM study by Dr. Sadowski's group, well ordered bismuth films on Si (111) were used as templates for the growth of thin organic films of pentacene. Making a good use of low-energy electron microscopy (LEEM) and STM, they found that pentacene nucleates on the Bi (001) substrate into a highly ordered, bulk-like crystalline layer, with the molecules "standing up" on the Bi surface, with the (001) plane as the growth front. Moreover, the Pn layer is aligned epitaxially with the Bi (001) surface having a "point-on-line" commensurate relation with the substrate, which is the first report on the epitaxial growth of pentacene. It was also found that the Pn/Bi (001) film crystallizes in the bulk-like structure directly from the first Pn layer, and that the diameter of the first-layer Pn islands exceeds as much as 200 mm, one of the largest pentacene islands reported up to date. (APL 86, 073109 (2005)) As an ongoing joint work with Professor Nakajima's group in this area, perylene-3.4.9.10-tetracarboxylic dianhydride (PTCDA) thin film grown on the hydrogen-terminated, vicinal Si (111) substrate was investigated by UHV STM, and the possible adsorption model has been proposed, in which the long axis of the 2D unit cell of PTCDA matches the vector (6, 2) of the H-Si(111) surface, and PTCDA lattice has a point-on-line coincidence with the H-Si (111) lattice. (Ref. 5 ) In the coming year we plan to extend our activities onto studying the growth mode, crystallographic and electronic transport properties of other organic thin films, such as perfluoropentacene, pentacene-quinone and rubrene.
We also note profitable collaboration in various researches with Professor Chen's group at IFCAM.
1. T. Nagao, J.T. Sadowski, M. Saito, S. Yaginuma, Y. Fujikawa, T. Kogure, T. Ohno, Y. Hasegawa, S. Hasegawa, and T. Sakurai,
"Nanofilm allotrope and phase transformation of ultra thin Bi film on Si (111)-7×7," Phys. Rev. Lett. 93, 105501 (2004).
2. T. Eguchi, Y. Fujikawa, K. Akiyama, T. An, M. Ono, T. Hashimoto, Y. Morikawa, K. Terakura, T. Sakurai, M. G. Lagally, and Y. Hasegawa,
"Imaging of All Dangling Bonds and Their Potential on the Ge/Si (105) Surface by Non-contact Atomic Force Microscopy,"
3. Kehui Wu, A. I. Oreshkin, Y. Takamura, Y. Fujikawa, T. Nagao, T.Briere, V. Kumar, Y. Kawazoe, R. F. Dou, Q. K. Xue and T. Sakurai,
"Step-by-step cooling of a two-dimensional Na gas on the Si (111)-(7×7) surface," Phys. Rev. B70, 195417 (2004).
4. S. Kuwano, Q. -Z. Xue, Y. Asano, Y. Fujikawa, Q. -K. Xue, Koji S. Nakayama, T. Nagao, and T. Sakurai,
"Bilayer-by-bilayer etching of 6H-GaN (0001) with Cl," Surf. Sci. 561, L213 (2004).
5. G. Sazaki, T. Fujino, J. T. Sadowski, N. Usami, T. Ujihara, K. Fujiwara, Y. Takahashi, E. Matsubara, T. Sakurai, and K. Nakajima
Epitaxial relation and island growth of perylene-3.4.9.10-tetracarboxylic dianhydride (PTCDA) thin film crystals on a hydrogen-terminated Si (111) substrate,"
Low Temperature Physics
Prof.Norio Kobayashi
(1990.5~ )【Staff Members】
Prof. Norio Kobayashi, Assoc. Prof. Takahiko Sasaki, Res. Assoc. Terukazu Nishizaki, Res. Assoc. Naoki Yoneyama, Res. Assoc. Kazutaka Kudo〈Supporting Staff : 1〉
【Research Activities】
Magnetic field driven order-disorder transition in YBa2Cu3Oy was investigated by using STM/STS from the microscopic point of view on the vortex structure. Direct imaging of the vortex structure demonstrated that the triangular lattice formed in the low field Bragg glass phase took a phase transition into the disordered phase (vortex glass phase) with increasing magnetic fields. In addition, systematic investigation of the relation between the macroscopic vortex state and microscopic electronic state was carried out in YBa2Cu3Oy in which substitation of by Zn and Ni took piace as an impurity in the Cu site.
An important result obtained in 2004 was the observation of the real space imaging of the metal-insulator phase separation near the first order Mott transition in the highly correlated organic conductors. The k type BEDT-TTF molecule based organic conductor has an effective half. filled band due to the BEDT-TTF molecule dimmer structure. The band width as compared to the on-site Coulomb interaction can be controlled by applying relatively low pressure and/or chemical substitution of modified molecules. The salts are classified to the band width controlled Mott system. The metal-insulator phase separation was found in the band width controlled k-(BEDT-TTF)2Cu[N(CN)2]Br by using the scanning micro region infrared reflectance spectrum measurement technique using synchrotron radiation at SPring-8. The frequency shift of the strongly EMV coupled molecular vibration was used as the local proof. This is the first direct observation of the real space imaging of the electronic inhomogeneity in micrometer size due to the electronic correlation.
1. N. Kobayashi, T. Nishizaki, K. Shibata, and T. Sasaki.
Vortex state in YBa2Cu3Oy crystals: vortex phase diagram and tunneling spectroscopy in magnetic field.
Physica B 346-347 (2004) 329 -333.
2. T. Nishizaki, K. Shibata, M. Maeda, T. Sato, and N. Kobayashi
Vortex order-disorder transition and the effect of Zn and Ni substitution in YBa2Cu3Oy.
Proceedings of Joint meeting of the International Symposium on JSPS Core-to-Core Integrated Action Initiative "Nanoscience and Engineering in Superconductivity" (CTC-NES) and The 4th International Symposium on Intrinsic Josephson Effect and Plasma Oscillations in High-Tc Superconductors (PLASMA 2004), (2004) pp. II-27 - II-30.
3. T. Sasaki, I. Ito, N. Yoneyama, N. Kobayashi, N. Hanasaki, H. Tajima, T. Ito, and Y. Iwasa. Electronic correlation in the infrared optical properties of the quasi-two-dimensional k-type BEDT-TTF dimer system.
Phys. Rev. B 69 (2004) 064508-1-064508-7.
4. T. Sasaki, N. Yoneyama, N. Kobayashi, Y. Ikemoto and H. Kimura.
Imaging phase separation near the Mott boundary of the correlated organic superconductors k-(BEDT-TTF)2X.
Phys. Rev. Lett. 92 (2004) 227001-1-227001-4. 5. N. Yoneyama, T. Sasaki and N. Kobayashi.
Substitution effect by deuterated donors on superconductivity in k (BEDT-TTF)2 Cu[N(CN)2] Br.
J. Phys. Soc. Jpn. 73 (2004) 1434-1437 【Plan】
Scientific target of the low temperature physics division is to resolve the mechanism and property of the superconductivity in high-Tc superconductors. Our research is carried out on the basis of the experimental techniques which have been built up so far in our laboratory; high quality single crystal growth, high precision bulk property measurement, and scanning tunnel microscopy and spectroscopy (STM/STS) at low temperature and in high magnetic fields. Main interest at present is the local electronic state and the relation to the bulk property of the superconductivity in the highly correlated electron system. We are planning to extend the measurement temperature and magnetic field regions of the STM/STS equipment. Strategic target is the discovery of the novel superconducting state in high magnetic fields, for example, spatial modulation of the superconducting order parameter along magnetic fields (FFLO state) and the magnetic field induced superconductivity. Specific programs in short term are running by using STM/STS as follows. (Ref.1 ) Local electronic modulation at the impurity atom (Ni, Zn) substituting the Cu site of YBa2Cu3Oy and the relation to the superconducting properties. (Ref.2 ) Charge density modulation on the one dimensional CuO chain of YBa2Cu3Oy and the relation to the superconductivity. (Ref.3 ) Spin and charge modulation structure in the novel one dimensional copper oxide ladder system Sr14Cu24O41. (Ref.4 ) Pseudo gap formation and the suppression in magnetic fields in Bi based copper oxide superconductors. (Ref.5 ) Charge order and the melting process in the quasi two dimensional organic conductors.
Low Temperature Condensed State Physics
Prof.Yoshihiro Iwasa
(2001.7~ )【Staff Members】
Prof. Yoshihiro Iwasa, Assoc. Prof. Yasujiro Taguchi, Res. Assoc. Taishi Takenobu, Res. Assoc. Shin-ichiro Kobayashi
【Research Activities】
Significant developments were achieved in 2004 in the area of organic transistors and carbon nanotubes.
In organic field effect transistors(OFET), we first demonstrated a method for intensive control of the channel carrier density using an interface doping technique with polar self-assembled monolayers (SAMs) (Ref.1 ). This observation was made not only on polycrystalline thin films (Ref.1 ) but also on single crystal devices (Ref.2 ), indicating that the interface doping in OFETs with SAMs is an intrinsic phenomenon free from extrinsic effects such as grain boundaries. We have also adopted an electrochemical transistor (ECT) technique to conducting polymers, and succeeded in a direct comparison between FET and electrochemical transistor operations in OFETs (Ref.4 ).
In carbon nanotubes, notable results were obtained in FET and optical properties. In multiwalled carbon nanotube devices, we have shown a gate electric field induced crossover from a localized to an extended state (Ref.3 ). In single-walled carbon nanotubes, on the other hand, we made a first demonstration of resonance enhancement of nonlinear optical response in collaboration with Okamoto group at University of Tokyo, and showed that the coherent process dominates in this enhancement (Ref.5 ).
1. S. Kobayashi, T. Nishikawa, T. Takenobu, S. Mori, T. Shimoda, T. Mitani, H. Shimotani, N. Yoshimoto, S. Ogawa, and Y. Iwasa
Control of carrier density by self-assembled monolayers in organic field-effect transistors Nat. Mater., 317 (2004) 317-322.
2. J. Takeya, T. Nishikawa, T. Takenobu, S. Kobayashi, Y. Iwasa, T. Mitani, C.Goldmann, C. Krellner, and B. Batlogg
Effect of polarized organosilane self-assembled monolayers on organic single-crystal field-effect transistors
Appl. Phys. Lett., 85 (2004) 5078-5080.
3. T. Kanbara, T. Iwasa, K. Tsukagoshi, Y. Aoyagi, and Y. Iwasa
Gate-induced crossover from unvconventinal metals to Fermi liquids in multiwalled carbon nanotubes.
Appl. Phys. Lett.. 85 (2004) 6404-6406. 4. H. Shimotani, G. Diguet, and Y. Iwasa
Direct comparison of field-effect and electrochemical doping in regioregular poly(3-hexylthiophene).
Appl. Phys. Lett. 86 (2005) 022104-1-3.
5. A. Maeda, S. Matsumoto, H. Kishida, T. Takenobu, Y. Iwasa, M. Shiraishi, M. Ata, and H. Okamoto
Large optical nonlinearity of semiconducting single-walled carbon nanotubes under resonant excitations
Phys. Rev. Lett. 94 (2005) 047404-1-4. 【Plan】
The aim of this group is to make novel functional materials and devices using nanostructured carbons, organic materials, and related systems. In the coming years, we are going to focus on the following three directions.
(1 ) Physics of organic electronics
(2 ) Properties of purified and composite carbon nanotubes
Neutron and γ-Ray Spectroscopy on Condensed Matters
Prof.
Kazuyoshi Yamada
(2003.4~ )【Staff Members】
Prof. Kazuyoshi Yamada, Assoc. Prof. Kenji Ohoyama, Res. Assoc. Masaki Fujita, Res. Assoc. Haruhiro Hiraka〈Supporting Staff : 2〉
【Research Activities】
(1) We have succeeded in observing the high-energy spin excitations in hole-doped superconductor La2-xBaxCuO4 (x=1/8). Our results showed a similarity dispersive excitation in YBCO system, suggesting a potential role of magnetism in the high-Tc mechanism.
(2) Effects of magnetic fields on static spin correlation were studied for the electron-doped superconductors Pr1-xLaCexCuO4. Results showed a weak coupling between the antiferromagnetic ordering and superconductivity.
(3) Impurity effects on spin correlations were studied for the electron-doped Pr1-xLaCexCuO4 in a wide Ce concentration range. We found that a static magnetic order is revealed to degrade upon Zn-doping, unlike the results of the hole-doped systems.
(4) We investigated static and dynamic lattice properties of lead-oxide-type relaxors, which show characteristic dielectric properties. With aid of neutron scattering experiments, it has been clarified that polar nano-regions play an important role in such the specific features in these relaxors.
(5) Magnetic excitations in the spin-density-wave state of Cr was studied by neutron scattering experiments. We found an unusual magnetic dispersion at low energy regions, which implies a different mechanism of the magnetic excitations from spin waves.
(6) We determined the crystal structures in the complex hydrides Li-N-H, which are promising hydrogen storage materials, by the neutron diffraction technique, and found that hydrogen atoms in the materials have a characteristic cage type structure.
(7) We studied the development of magnetic correlations in rare earth compounds RB2C2, which exhibit characteristic and complicated magnetic and quadrupolar orderings.
1. Magnetic field effect on the static antiferromagnetism of the electron-doped superconductor Pr1-xLaCexCuO4 (x=0.11 and 0.15)
M. Fujita, M. Matsuda, S. Katano, K. Yamada Phys. Rev. Lett. 93, (2004) 147003/1-147003/4
2. Quantum Magnetic Excitations from Stripes in Copper-Oxide Superconductors
J. M. Tranquada, H. Woo, T. G. Perring, H. Goka, G. D. Gu, G. Xu, M. Fujita, K. Yamada Nature 429, (2004) 534 - 538
3. Revised crystal structure model of Li2NH by neutron powder diffraction K. Ohoyama, Y. Nakamori, S. Orimo and K. Yamada
J. Phys. Soc. Jpn. 74,(2005) 483-487. 4. Xu, GY; Zhong, Z; Hiraka, H; Shirane, G
Three-dimensional mapping of diffuse scattering in Pb(Zn1/3Nb2/3)O-3-xPbTiO(3) Rev. B, 70, (2004) 174109
5. Hiraka, H; Boni, P; Yamada, K; Park, S; Lee, SH; Shirane, G Characterization of low-energy magnetic excitations in chromium Phys. Rev. B,70, (2004) 144413
【Plan】
(1) Measurement of an overall spin excitations in electron-doped superconductors in order to reveal universal role of magnetism in the mechanism of high-Tc superconductivity.
(2) Clarification of the close connection between magnetism and superconductivity by measuring spin dynamics in the magnetic-impurity-doped cuprate superconductors La2-xSrxCuO4.
(3) Study of competition between antiferromagnetic and antiferroquadrupolar interactions by observing spin and lattice dynamics.
(4) Structural study of complex hydrides and dielectric materials
(5) The reconstruction of the Kinken-neutron-spectroemter (AKANE) since 2003 will be completed by June 2005.
(6) Development of new experimental techniques of neutron scattering: beam focusing by supermirrors, high magnetic field by pulse magnets, 2D detector system.
Physics of Crystal Defects
Prof.Kazuo Nakajima
(Concurrently)【Staff Members】
Prof. Kazuo Nakajima, Assoc. Prof. Ichiro Yonenaga 【Research Activities】
In order to establish the knowledge of defects in semiconductors and also to apply them to new functions, the fundamental properties of various kinds of defects in various semiconductors, mainly in silicon and silicon-germanium, have been investigated for controlling their properties for applications.
The paper (Ref.1 ) reports the Czochralski growth of bulk crystals of SixGe1-x alloys in the whole composition range and their fundamental properties clarified as a distorted atomistic structure, electrical and thermal transportations, impurity lattice-site occupation, and thermo-mechanical strengths, originating from the alloying effects. In the paper (Ref.2 ) the photoluminescence characteristics of fresh dislocations introduced by plastic deformation into GaN bulk single crystals are reported in a view point for developing the high efficiency blue light emitting. The paper (Ref.3 ) summarizes the direct observation of atomistic structures of dislocations and defects in GaAs by high-resolution transmission electron microscopy. In the paper (Ref.4 ) the diffusion of Au impurity in Si is reported under the effects of B impurity in high concentrations and dislocations and is discussed in a kick-out mechanism together with segregation at dislocations. This result addresses the recent trend of the applications of low resisitivity Si crystals for nano-aturized devices. The paper (Ref.5 ) reports the dynamic interaction between dislocations and various impurities in Si in a viewpoint of out-looking the future trends, challenges and demands for strain control at the film/substrate interface.
1 . I. Yonenaga
Growth and Fundamental Properties of SiGe Bulk Crystals J. Cryst. Growth 275 (2005) 91-98.
2. I. Yonenaga, H. Makino, S. Itoh and T. Yao
Photoluminescence study of GaN with dislocations introduced by plastic deformation Physica Status Solidi (c) 2 (2005) 1817-1821.
3. I. Yonenaga
Atomic structure of defects in semiconductors
"Encyclopedia of Nanoscience and Nanotechnology, Vol. 1", edited by H. S. Nalwa, American Scientific Publishers, 2004, p. 135-145.
4. A. Rodriguez and H. Bracht and I. Yonenaga
Impact of high B concentrations and high dislocation densities on Au diffusion in Si J. Appl. Phys. 95 (2004) 7841-7849.
5. I. Yonenaga, T. Taishi, X. Huang and K. Hoshikawa
Dislocation-Impurity Interaction in Czochralski-Grown Si heavily doped with B and Ge J. Cryst. Growth 275 (2005) e501 - e505.
【Plan】
The aim is to clarify the fundamentals on a variety of properties and elementary processes of defects and their mutual reactions in semiconductors in order to provide insights for developing the semiconductor technology with optimized control engineering of defects and to establish the science of imperfection in materials finally.
In the next 5 years, the current researches will continue, i.e., the electrical, optical and dynamic properties of various defects and their degradation modification under a variety of external conditions should be clarified physically in almost all kinds of available semiconductors and the applications of their nano/quantum features to create functional devices. In addition, the followings have been kicked off
(1) To investigate the mechanism of defect induction by strains at hetero-structural interface and to develop as stress/strain control engineering in the elemental semiconductors as Si, Ge, and so on, and then other kinds of semiconductors.
(2) To clarify the magnetic-field effects on defect properties.
(3) To create next-generation IV-IV compound semiconductors and to develop the new devices with their structural imperfections (perturbations and defects).
Many novel semiconductors have been proposed and are in research at present. The situation will continue in future. Thus, the survey of such materials on their status, trend, challenge and demands, should be inevitably important for outlook of the suitable direction in future.
In the long term, science of imperfections in a variety of materials, including semiconductors, metals, oxides, is aimed to be established, since material creation and functions can be performed by suitable utilization of such imperfections.
