MRS Japan News　Vol.19 No.2  May 2007

　In the ceramic and semiconductor materials, nano-particles have been expected to be important precursors to fabricate their nano-structured materials. I would like to state that Nano-particles (0D solid) have not always necessary, or sometimes even inappropriate as their precursors to fabricate shaped 1D, 2D, or 3D Nano-materials.
　When nano-particles can be fabricated from highly energetic species like gasses, vapors, molecules, clusters, atoms, and ions as the precursors, their driving forces between such high energetic species and the nano-particles (≡nano-sized solids) can be used also for the consolidation; shape formation and shape fixing of materials. It seems to have less necessity to stop the reaction at the stage to synthesize the compound in nano-sized particles. Once nano-particles would be fabricated only their surface energies can be usable for the following processes. Surface energies are not enough to consolidate the particles into the shaped materials therefore post-firing at a high temperature is essential in those powder/particle processings even using nano-particles with 5-100nm in size. In the solution processings, the species in solutions have much less energies than those in gasses, thus it is more difficult to form shaped solid materials directly from solution species. Solution processes, therefore, would be generally used for the synthesis of compounds in powder/particle (0D solid). However, we can fabricate those shaped (1D, 2D, and 3D) nano-structured materials directly from solution(s) when we can use the driving force to synthesize the compound AB from the precursor solution(s) containing A and/or B. When we can activate the reaction A＋B＝AB at the local point and/or can move the point, we can fabricate shaped, patterned and/or integrated nano-structured materials directly in/from the solution(s) without any post-firing. Those direct fabrication of shaped materials has been called as “Soft (Solution) Processing,” has been developed in our group.　　

HomePage: http://www.msl.titech.ac.jp/〜yoshimura/

References

M. Yoshimura, Powder-Less Processing for Nano-Structured Bulk Ceramics: Realization of Direct Fabrication from Solutions and/or Melts, J. Ceram. Soc. Japan, 114 ［11］ 888-895 (2006)）

Fig.1　Comparison of “direct patterning” with “normal mask-less patterning” method for ceramics. Normal patterning methods require firing for the consolidation and fixing of powders or their precursors like gels, sols, etc.

Fig.2　Photographs of letters patterned by CaWO4 on a paper substrate (ａ) under normal light conditions and (b) that exposed to UV radiation at room temperature showing a blue luminescence.

Fig.3　High-resolution TEM Image of HfO2-Al2O3-GdAlO3 (sample annealed at 1273K for 6hr).

　Polycrystalline bismuth microwire thermoelectric elements having 1 to 100μm diameters and 1mm length have been developed. To eliminate contact resistance between all wire edges and electrode of the microwire array element, Ti/Cu thin film layers were deposited by ion plating technique. Thermoelectric properties such as Seebeck coefficient, resistivity and thermal conductivity were successfully estimated. As a next step, we plan to fabricate bismuth nanowire thermoelectric element (1D structure) with quartz glass template to improve the performance with quantum effect.

図-1　熱電変換素子の概念図

図-2　マイクロワイヤー素子の概念図

図-3　マイクロワイヤー素子の作製方法

図-4　マイクロワイヤー素子端部の電極層

図-5　アルミニウム陽極酸化によるナノホール（アルミナテンプレート）

図-6　開発を進めている石英ガラス製テンプレート

References

1) 日本セラミックス協会日本熱電学会編, 熱電変換材料, 日本工業新聞社 (2005)
2) L.D. Hicks, M.S. Dresselhaus, Phys. Rev. B, Vol.47, 12727 (1993)
3) R. Venkatasubramanian et al., Nature, Vol.413, 597 (2001)
4) T.C. Harman et al., Science, Vol.297, 2229 (2002)
5) H. Ohta et al., Nature Mater. Online, Jan., 21 (2007)
6) Y. Hasegawa, Y. Ishikawa et al., Appl. Phys. Lett., 85, 917 (2004)
7) Y. Hasegawa, H. Nakano et al., J. Appl. Phys., 101, 033704 (2007)
8) Y. Hasegawa, Y. Ishikawa, H. Shirai, H. Morita, A. Kurokouchi, K. Wada, T. Komine and H. Nakamura, Rev. Sci. Instrum., 76, 113902 (2005)
9) H. Iwasaki, H. Morita, et al., Proc. 25th Int. Conf. on Thermoelectrics, pp.220-223 (2006)

　Advanced Materials Science Research Center was established in 1996 as the research center of materials science at Kanazawa Institute of Technology. Since its inception in 1996, the AMSRC was supported by “High-Tech Research Center” Project for Private Universities: matching fund subsidy from MEXT (Ministry of Education, Culture, Sports, Science and Technology) for 10 years. By bringing together researchers on bulk materials and thin films from the fields of mechanical engineering, electrical engineering, materials science, and applied physics, the center has performed world-class multidisciplinary researches. In this report, the activities of AMSRC are reviewed.

写真-1　高度材料科学研究開発センターの外観

写真-2　超高真空対応カルーセル型スパッタリング装置

写真-3　プラズマプロセス複合スパッタリング装置およびプラズマプロセスモニタ

写真-4　超高真空対応スパッタアップ型スパッタリング装置

写真-5　XPS system

Infromation

■Call for the Session Themes of the MRS-J Symposium 2007
　Proposals of the session themes and chairs for the 18th Symposium to be held in December 7-9, 2007 at the site of Nihon University’s Ochanomizu Campus are solicited. Deadline of the proposals is May 10, 2007. Further informations will be obtained: http://www.mrs-j.org/

■Doyama Symposium
　The 17th IKETANI International Conference on “Dreams, Creation and Realization of Materials Saving the Humankind” will be held at the University of Tokyo, Tokyo, Japan from September 5 through 8, 2007. This Conference is also planned in commemoration of the 80th birthday of Prof. Emeritus of the University of Tokyo, Dr. Masao Doyama and will be supported by the Iketani Science and Technology Foundation. Further information: http://www.iketani2007.jks.ynu.ac.jp.