Kyushu University Academic Staff Educational and Research Activities Database
Researcher information (To researchers) Need Help? How to update
Yoshifumi Ikoma Last modified date:2019.08.06

Assistant Professor / Advanced Materials Physics
Department of Materials Science and Engineering
Faculty of Engineering


Graduate School
Undergraduate School


E-Mail
Homepage
http://zaiko6.zaiko.kyushu-u.ac.jp/
Academic Degree
Doctor of Engineering
Field of Specialization
Thin film growth, epitaxial growth, semiconductor nano-structure, bulk nanostructured semiconductor materials
Outline Activities
1. Bulk nanostructured semiconductor materials by using giant straining process
Nanocrystalline semiconductor materials exhibit unique electrical and optical properties. We investigate the formation of bulk nanostructured semiconductor materials (Si, Ge, GaAs, etc.) by using high-pressure torsion.
2. Thin film growth by using pulse jet CVD
The formation of semiconductor multiple heterostructures on Si substrates is of great interest to those building high-performance electronic and optoelectronic devices. We have reported the epitaxial growth of ultrathin (~3 nm) SiC films and SiC/Si multilayers on Si(100) by supersonic free jet CVD. We have also investigated the formation of semiconductor nanopores by utilizing SiC/Si heteroepitaxial growth, and Si-based nanowires on Si substrates by organosilane pulse jet CVD.
Research
Research Interests
  • Formation of semiconductor bulk nanostructured materials by using High-Pressure Torsion
    keyword : HPT, nanocrystalline semiconductor materials
    2011.04.
  • Semiconductor nanocrystal growths by Au-catalyzed pulse jet CVD
    keyword : VLS growth
    2012.04~2013.03.
  • Semiconductor nanopore formation by utilizing SiC/Si heteroepitaxial growth
    keyword : nanopore
    2005.04~2013.03A nanometer-sized pore (nanopore) is of great interest for a possible application to molecular sensors such as DNA sequencers. The solid-state nanopore is mainly fabricated by utilizing ion beam method. However, this techniques are not suitable for mass production. We introduced the pits into the top Si layers of Silicon-on-Insulator (SOI) substrates by SiC/Si heteroepitaxy, and investigate the nanopore formation onto the thin Si layer of SOI substrates..
  • SiC/Si nanostructures by supersonic free jet CVD
    keyword : Si-based nano structures, supersonic free jet CVD
    1999.04~2013.03The formation of semiconductor quantum devices on Si substrates is of great interest to those building high-performance electronic devices. We focus on the growths of nano-scale SiC/Si multilayer structures utilizing supersonic free jet CVD. .
Academic Activities
Papers
1. Yoshifumi Ikoma, Severe Plastic Deformation of Semiconductor Materials Using High-Pressure Torsion, Materials Transactions, 10.2320/matertrans.MF201907, 60, 7, 1168-1176, 2019.07.
2. Yoshifumi Ikoma, Bumsoo Chon, Terumasa Yamasaki, Kazutoshi Takahashi, Katsuhiko Saito, Qixin Guo, and Zenji Horita, Crystal and electronic structural changes during annealing in severely deformed Si containing metastable phases formed by high-pressure torsion, Applied Physics Letters, 10.1063/1.5038160, 113, 101904, 2018.09.
3. Yoshifumi Ikoma, Kazuki Kumano, Kaveh Edalati, Martha R. McCartney, David J. Smith, Zenji Horita, High-resolution transmission electron microscopy analysis of nanograined germanium produced by high-pressure torsion, Materials Characterization, 10.1016/j.matchar.2017.08.011, 132, 132-138, 2017.10.
4. Yoshifumi Ikoma, Kazuki Kumano, Kaveh Edalati, Katsuhiko Saito, Qixin Guo, Zenji Horita, Phase transformation of germanium by processing through high-pressure torsion: strain and temperature effects, Philosophical Magazine Letters, 10.1080/09500839.2016.1266099, 97, 1, 27-34, 2017.01.
5. Yoshifumi Ikoma, Takamitsu Toyota, Yoshimasa Ejiri, Katsuhiko Saito, Qixin Guo, Zenji Horita, Allotropic phase transformation and photoluminescence of germanium nanograins processed by high-pressure torsion, J. Mater. Sci., 10.1007/s10853-015-9328-y, 51, 1, 138-143, 2016.01.
6. Yoshifumi Ikoma, Kazunori Hayano, Kaveh Edalati, Katsuhiko Saito, Qixin Guo, Zenji Horita, Toshihiro Aoki, David J. Smith, Fabrication of nanograined silicon by high-pressure torsion, J. Mater. Sci., 10.1007/s10853-014-8250-z, 49, 19, 6565-6569, 2014.10.
7. Yoshifumi Ikoma, Yoshimasa Ejiri, Kazunori Hayano, Katsuhiko Saito, Qixin Guo, Zenji Horita, Nanograin formation of GaAs by high-pressure torsion, Philos. Mag. Lett., 10.1080/09500839.2013.852265, 94, 1, 1-8, 2014.01.
8. Yoshifumi Ikoma, Kazunori Hayano, Kaveh Edalati, Katsuhiko Saito, Qixin Guo, and Zenji Horita, Phase transformation and nanograin refinement of silicon by processing through high-pressure torsion, Appl. Phys. Lett., 101, 12, 121908, 2012.09.
9. Yoshifumi Ikoma, Hafizal Yahaya, Keiji Kuriyama, Hirofumi Sakita, Yuta Nishino, and Teruaki Motooka, Semiconductor nanopores formed by chemical vapor deposition of heteroepitaxial SiC films on SOI(100) substrates
, J. Vac. Sci. Technol. B, 10.1116/1.3646471, 29, 6, 062001-1 - 062001-5, 2011.11.
10. Yoshifumi Ikoma, Ryousuke Okuyama, Makoto Arita, Teruaki Motooka, Formation and structural characterization of nanocrystalline Si/SiC multilayers grown by hot filament assisted chemical vapor deposition using CH3SiH3 gas jets, Thin Solid Films , doi:10.1016/j.tsf.2009.10.127, 518, 14, 3759–3762, 518 (14) 3759–3762, 2010.04.
11. Yoshifumi Ikoma, Takayoshi Masaki, Shinji Kawai, and Teruaki Motooka, Formation of silicon nanodots from dysprosium-doped amorphous SiCxOy films grown by hot-filament assisted chemical vapor deposition of CH3SiH3 and Dy(DPM)3 gas jets, Applied Surface Science, vol. 253, No. 31, pp. 8657-8660., 2007.08.
12. SiC/Si-dots multilayer structures formed by supersonic free jets of CH3SiH3 and Si3H8
Yoshifumi Ikoma Ryota Ohtani Nobuaki Matsui and Teruaki Motooka
J. Vac.Sci. Technol. B
Vol.21 6(2003)pp.2492-2495..
Presentations
1. Yoshifumi Ikoma, Bumsoo Chon, Terumasa Yamasaki, Katsuhiko Saito, Qixin Guo, Martha R. McCartney, David J. Smith, Zenji Horita, Microstructural and Optical Properties of Nanograined Si Processed by High-Pressure Torsion
, The 5th International Conference on Nanomechanics and Nanocomposites (ICNN5), 2018.08.
2. Yoshifumi Ikoma, Terumasa Yamasaki, Katsuhiko Saito, Qixin Guo, Zenji Horita, Production of bulk nanograined Si by high-pressure torsion at various pressures, TMS2018 147th Annual Meeting & Exhibition, 2018.03.
3. Yoshifumi Ikoma, Kazuki Kumano, Kaveh Edalati, Martha R. McCartney, David J. Smith, Zenji Horita, TEM observations of Ge processed by high-pressure torsion, International Workshop on Giant Straining Process for Advanced Materials (GSAM2017), 2017.09.
4. Yoshifumi Ikoma, Kazuki Kumano, Bumsoo Chon, Kaveh Edalati, Martha R. McCartney, David J. Smith, Zenji Horita, Microstructure Analysis of Bulk Nanograined Germanium Obtained by High-Pressure Torsion: Temperature Dependence, The 15th International Conference on Advanced Materials (IUMRS-ICAM2017), 2017.08, Nanocrystalline germanium (nc-Ge) has unique optical properties such as photoluminescence at room temperature. Nc-Ge is mainly prepared by bottom-up techniques such as sputtering and ion implantation. Severe plastic deformation (SPD) is a top-down technique and is promising for producing ultrafine grained materials. Among various SPD processes, high-pressure torsion (HPT) can apply to semiconductor materials such as Si and GaAs. Recently, we have reported the HPT processing of Ge, and found the formation of nanograins having a diamond cubic Ge-I and tetragonal Ge-III phases. We also found that metastable Ge-IV having a body-centered-cubic structure appeared from the sample just after cryogenic HPT-processing. However, the microstructures of the samples after HPT processing at cryogenic temperature are not fully understood. In this study, we investigated the microstructure observations of the HPT-processed samples by means of high resolution transmission electron microscopy (HRTEM).
The samples processed at room temperature were composed of Ge-I and Ge-III nanograins. HRTEM observations revealed that there existed lattice defects such as dislocations, stacking faults, and nanotwins in the nanograins. The metastable Ge-III phase disappeared and only Ge-I was observed after annealing at 573 K. In the case of cryogenic HPT-processing, the sample was mainly composed of Ge-I nanograins. Although no appreciable metastable phase was observed from XRD profiles of the cryogenic HPT-processed samples after keeping at room temperature, small amount of Ge-III nanograins having a size of several nanometers and amorphous phase were observed in the HRTEM images. These results indicate that the formation of metastable phases strongly depends not only on the imposed strain but also on the temperature for HPT processing..
5. Yoshifumi Ikoma, Kazuki Kumano, Bumsoo Chon, Kaveh Edalati, Martha R. McCartney, David J. Smith, Zenji Horita, HRTEM observations of nanograined germanium produced by high-pressure torsion, The 7th International Conference on Nanomaterials by Severe Plastic Deformation, 2017.07.
6. Yoshifumi Ikoma, Yoshimasa Ejiri, Katsuhiko Saito, Qixin Guo, Zenji Horita, Production of nanograined ZnTe by severe plastic deformation under high pressure, 9th Pacific Rim International Conference on Advanced Materials and Processing (PRICM9), 2016.08.
7. Yoshifumi Ikoma, HPT processing of germanium at cryogenic temperature, International Workshop on Giant Straining Process for Advanced Materials (GSAM2016), 2016.07.
8. Yoshifumi Ikoma, Takamitsu Toyota, Katsuhiko Saito, Qixin Guo, Zenji Horita, Production of Nanograined Ge Using Severe Plastic Deformation under High Pressure, TMS2016 145th ANNUAL MEETING & EXHIBITION, 2016.02.
9. Yoshifumi Ikoma, Katsuhiko Saito, Qixin Guo, Zenji Horita, Formation of metastable phases and nanograined silicon by severe plastic deformation under high pressure, 11th China SoG Silicon and PV Power Conference, 2015.11.
10. Y. Ikoma, Formation of metastable phases and nanograins of Si and Ge by high-pressure torsion, International Workshop on Giant Straining Process for Advanced Materials (GSAM2015), 2015.09.
11. Yoshifumi Ikoma, Takamitsu Toyota, Yoshimasa Ejiri, Kazunori Hayano, Katsuhiko Saito, Qixin Guo, Zenji Horita, Formation of metastable phases in germanium by high-pressure torsion, The 6th International Conference on Nanomaterials by Severe Plastic Deformation (NanoSPD6), 2014.07.
12. Y. Ikoma, K. Eladati, K. Hayano, K. Saito, Q. Guo, Z. Horita, Formation of Metastable Phases of Silicon Processed by High-pressure Torsion, TMS 2014 143rd Annual Meeting & Exhibition, 2014.02.
13. Yoshifumi Ikoma, Pulsed supersonic jet CVD: thin films, nanopores, and nanowires, 2013 International Workshop on Novel Materials and Devices, 2013.09.
14. Yoshifumi Ikoma, Kazunori Hayano, EDALATI KAVEH, Katsuhiko Saito, Qixin Guo, Zenji Horita, Production of Nanograined Silicon Using High-pressure Torsion, 8th Pacific Rim International Congress on Advanced Materials and Processing (PRICM-8), 2013.08.