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Naoki Ohashi

Naoki Ohashi
Affiliation:
Specialty:
Optoelectronics of Oxide and Nitride Semiconductors
Academic degree:
Ph.D. Tokyo Institute of Technology (1992)

Education & Working History

2007 Director, Optronic Materials Center, NIMS
2006 Group Leader, Optoelectronics Group, IMS
2001 Senior Researcher, Electroceramics Group, NIMS
2000 Senior Researcher, Natl. Inst. Res. Inorgan. Mater. (NIRIM)
1999 Visiting Scholar, Dept. Mater. Sci. Eng., Massachusetts Institute of Technology, USA
1993 Assistant Prof., Inorg. Mat., Tokyo Institute of Technology
1992 Post Doctoral Research Associate, Inorg. Mat., Tokyo Institute of Technology
1992 Ph.D., Inorganic Materials, Tokyo Institute of Technology

Research History

Naoki OHASHI has been investigated structure-composition-property relationships in oxide ceramics, including semiconductor, piezoelectric and ferroelectric oxide, and superconductors. Recently, he has expanded his field to nitride semiconductors and photocatalytic materials, including nano-structured materials.

He is mostly interested in the defects and interface in oxide materials. His most outstanding achievement was found in the research on hydrogen impurity in oxide. He has firstly found that hydrogen impurity in zinc oxide cause drastic change in optical properties. His reports on hydrogen impurity in ZnO have inspired interest in the hydrogen doping effect to semiconductors and a lot of researches have been initiated in the world. He expanded his study on light element doping to oxide into the field of photocatalytic oxides and his paper was awarded as the top cited article in a world class journal Catalyst Today. For his achievements including those findings and developments, he received "Richard M. Fulrath Award" from the American Ceramic Society in 2009.

He has many contributions to ceramic and its related engineering. He has published many patents in the field of oxide electronics. Many companies are interested in his patents and, now, he is working for several joint projects with some companies to utilize his technology in industry.

Related Links

Awards

Selected Papers

  1. Polarity-dependent photoemission spectra of wurtzite-type zinc oxide
    Ohashi N, Adachi Y, Ohsawa T, Matsumoto K, Sakaguchi I, Haneda H, Ueda S, Yoshikawa H, Kobayashi K
    Appl Phys Lett, 2009; 94(12): 122102.
  2. Growth of bulky single crystalline films of (Zn,Mg)O alloy semiconductors by liquid phase epitaxy
    Kotayashi J, Sekiwa H, Miyamoto M, Sakaguchi I, Wada Y, Sekiguchi T, Adachi Y, Haneda H, Ohashi N
    Cryst Growth Des, 2009; 9(2): 1219-1224.
  3. Electronic states in zinc magnesium oxide alloy semiconductors: Hard X-ray photoemission spectroscopy and density functional theory calculations
    Ohsawa T, Adachi Y, Sakaguchi I, Matsumoto K, Haneda H, Ueda S, Yoshikawa H, Kobayashi K, Ohashi N
    Chem Mater, 2009; 21(1): 144-150.
  4. Lowered stimulated emission threshold of zinc oxide by hydrogen doping with pulsed argon-hydrogen plasma
    Ohashi N, Wang YG, Ishigaki T, Wada Y, Taguchi H, Sakaguchi I, Ohgaki T, Adachi Y, Haneda H
    J Cryst Growth, 2007; 306(2): 316-320.
  5. Origin of visible-light-driven photocatalysis: A comparative study on N/F-doped and N-F-codoped TiO2 powders by means of experimental characterizations and theoretical calculations
    Li D, Ohashi N, Hishita S, Kolodiazhnyi T, Haneda H
    J Solid State Chem, 2005; 178(11): 3293-3302.
  6. Pyrogenic iron(III)-doped TiO2 nanopowders synthesized in RF thermal plasma: Phase formation, defect structure, band gap, and magnetic properties
    Wang XH, Li JG, Kamiyama H, Katada M, Ohashi N, Moriyoshi Y, Ishigaki T
    J Am Chem Soc, 2005; 127(31): 10982.
  7. Visible-light-driven N-F-codoped TiO2 photocatalysts. 1. Synthesis by spray pyrolysis and surface characterization
    D. Li, H. Haneda, S. Hishita, N. Ohashi
    Chem Mater, 2005; 17(10): 2588–2595.
  8. Passivation of active recombination centers in ZnO by hydrogen doping
    Ohashi N, Ishigaki T, Okada N, Taguchi H, Sakaguchi I, Hishita S, Sekiguchi T, Haneda H
    J Appl Phys, 2003; 93(10): 6386.
  9. Isothermal capacitance transient spectroscopy for deep levels in Co- and Mn-doped ZnO single crystal
    Ohashi N, Tanaka J, Haneda H, Ozawa M, Ohgaki MT, Tsurumi T
    J Mater Res, 2002; 17(6): 1529-1535.
  10. Effect of hydrogen doping on ultraviolet emission spectra of various types of ZnO
    Ohashi N, Ishigaki T, Okada N, Sekiguchi T, Sakaguchi I, Haneda H
    Appl Phys Lett, 2002; 80(16): 2869.
  11. Effect of hydrogenation on ZnO luminescenc
    Sekiguchi T, Ohashi N, Terada Y
    Jpn J Appl Phys, 1997; 36(Part2): L289.
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