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-implanted GaN film studied by a monoenergetic positron beamLi, X. F.*; Chen, Z. Q.*; Liu, C.*; Zhang, H.; Kawasuso, Atsuo
Journal of Applied Physics, 117(8), p.085706_1 - 085706_6, 2015/02
Times Cited Count：23 Percentile：68.13(Physics, Applied)Vacancy-type defects in C-implanted GaN were probed using a slow positron beam. The increase of Doppler broadening S parameter indicates introduction of arge vacancy clusters. Post-implantation annealing at temperatures up to 800
C makes these vacancy clusters to agglomerate into microvoids. The vacancy clusters or microvoids show high thermal stability, and they are only partially removed after annealing up to 1000C. Amorphous regions are observed by high resolution transmission electron microscopy measurement, which directly confirms that amorphization is induced by C-implantation. The disordered GaN lattice is possibly due to special feature of carbon impurities, which enhance the damage buildup during implantation.
Kawasuso, Atsuo; Yoshikawa, Masahito; Ito, Hisayoshi; Krause-Rehberg, R.*; Redmann, F.*; Higuchi, Takatoshi*; Betsuyaku, Kiyoshi*
Physica B; Condensed Matter, 376-377, p.350 - 353, 2006/04
Times Cited Count：13 Percentile：52.05(Physics, Condensed Matter)In this presentation, we report identification of vacancy defects in cubic and hexagonal SiC irradiated with fast electrons through electron-pisitron momentum distribution measurements and theoretical analyses. In cubic SiC isolated silicon vacancies are responsible for positron trapping. The lifetime of positrons trapped at silicon vacancies is prolonged due to the outward lattice relaxation. Because of the local tetrahedral symmetry of silicon vacancies, the observed momentum distributions are consistently explained. In the case of hexagonal SiC, one particular vacancy defects appearing after annealing of isolated silicon vacancies have dangling bonds along the c-axis. From the enhancement of positron annihilation probability with carbon 1s electrons, the above defects are attributed to carbon-vacancy-antisite-carbon complexes.
Kawasuso, Atsuo; Yoshikawa, Masahito; Ito, Hisayoshi; Chiba, Toshinobu*; Higuchi, Takatoshi*; Betsuyaku, Kiyoshi*; Redmann, F.*; Krause-Rehberg, R.*
Physical Review B, 72(4), p.045204_1 - 045204_6, 2005/07
Times Cited Count：16 Percentile：55.78(Materials Science, Multidisciplinary)Two-dimensional angular correlation of annihilation radiation (2D-ACAR) and coincidence Doppler broadening (CDB) of annihilation radiation measurements have been performed on electron-irradiated n-type 3C SiC in which isolated silicon vacancies are responsible for positron trapping. After irradiation, the intensity of CDB spectrum increased and decreased in low and high momentum regions, respectively. These fetures were explained by the theoretical calculation considering silicon vacancies. The center region of 2D-ACAR spectra became isotropic after iradiation, while the overall anisotropies extending within the Jones zone were conserved suggesting that isolated silicon vacancies have the tetrahedral symmetry as expected from the previous electron spin resonance study.
SiCKawasuso, Atsuo; Chiba, Toshinobu*; Higuchi, Takatoshi*
Physical Review B, 71(19), p.193204_1 - 193204_4, 2005/05
Times Cited Count：15 Percentile：53.97(Materials Science, Multidisciplinary)Electron-positron momentum distributions associated with vacancy defects in 6H SiC after irradiation with 2 MeV electrons and annealing at 1000
have been studied using angular correlation of annihilation radiation (ACAR) measurements. It was confirmed that the above vacancy defects have dangling bonds along the c-axis and the rotational symmetry around it. The first principles calculation suggests that the vacancy defects are attributable to either carbon-vacancy-carbon-antisites complexes or silicon-vacancy-nitrogen pairs, while isolated carbon vacancies, silicon vacancies and nearest neighbor divacancies are ruled out.
Kawasuso, Atsuo; Weidener, M.*; Redmann, F.*; Frank, T.*; Sperr, P.*; K
gel, G.*; Yoshikawa, Masahito; Ito, Hisayoshi; Krause-Rehberg, R.*; Triftsh
user, W.*; et al.
Silicon Carbide, p.563 - 584, 2004/00
no abstracts in English
Chen, Z. Q.; Yamamoto, Shunya; Maekawa, Masaki; Kawasuso, Atsuo; Yuan, X. L.*; Sekiguchi, Takashi*
Journal of Applied Physics, 94(8), p.4807 - 4812, 2003/10
Times Cited Count：168 Percentile：96.67(Physics, Applied)no abstracts in English
Kawasuso, Atsuo; Yoshikawa, Masahito; Maekawa, Masaki; Ito, Hisayoshi; Chiba, Toshinobu*; Redmann, F.*; Rehberg, R. K.*; Weidner, M.*; Frank, T.*; Pensl, G.*
Materials Science Forum, 433-436, p.477 - 480, 2003/08
no abstracts in English
levels in electron-irradiated 4H-SiC studied by positron annihilation and deep-level transient spectroscopyKawasuso, Atsuo; Redmann, F.*; Krause-Rehberg, R.*; Weidner, M.*; Frank, T.*; Pensl, G.*; Sperr, P.*; Triftshuser, W.*; Ito, Hisayoshi
Applied Physics Letters, 79(24), p.3950 - 3952, 2001/12
Times Cited Count：39 Percentile：79.52(Physics, Applied)no abstracts in English
Redmann, F.*; Kawasuso, Atsuo; Petters, K.*; Ito, Hisayoshi; Krause-Rehberg, R.*
Physica B; Condensed Matter, 308-310, p.629 - 632, 2001/12
Times Cited Count：3 Percentile：22.29(Physics, Condensed Matter)no abstracts in English
Kawasuso, Atsuo; Weidner, M.*; Redmann, F.*; Frank, T.*; Sperr, P.*; Krause-Rehberg, R.*; Triftshuser, W.*; Pensl, G.*
Physica B; Condensed Matter, 308-310, p.660 - 663, 2001/12
Times Cited Count：13 Percentile：57.97(Physics, Condensed Matter)no abstracts in English
SiC epilayers studied by positron annihilation and deep level transient spectroscopyKawasuso, Atsuo; Redmann, F.*; Krause-Rehberg, R.*; Frank, T.*; Weidner, M.*; Pensl, G.*; Sperr, P.*; Ito, Hisayoshi
Journal of Applied Physics, 90(7), p.3377 - 3382, 2001/10
Times Cited Count：42 Percentile：81.14(Physics, Applied)no abstracts in English
*; *; *; *; Hasegawa, Makoto; Hirano, Koichiro
JNC TY9400 2000-007, 50 Pages, 2000/03
JNC-TY9400-2000-007.pdf:1.29MB
no abstracts in English
; Ueno, Fumiyoshi
JNC TN9400 2000-017, 10 Pages, 2000/03
JNC-TN9400-2000-017.pdf:0.58MB
lt is difficult to get hold the behave of growth of cavity which nucleates in grain boudaly in experimental observation. lt is considerd that numerical simulation is effective for the grasp of behave of cavity growth, because it is able to grasp the microscopic behavior of internal material whici is hardly observation. We examine the factor that the diffusive ratio and the stress etc., affected growth of cavity on grain boundary with numerical simulation using diffusive equation. As the result, a following knowledge was obtained. (1)With dominant of grain boundary diffusion, the shape of cavity transitions from quasi-equilibrium to crac-like. ln other hand, with dominant of surface diffusion, cavity grows up with initial shape. (2)With dominate of grain boundary diffusion, it accelerates the growth rate of the cavity near the tip by grain boundaly diffusion induced stressing perpendicular to gain boundary (3)With dominant of surface diffusion, the distribution of chemical potential is uniformity on cavity surface. ln other hand, with dominant of grain boundary diffusion compare to that of surface diffusion, the gradient of chemical potential is increased at the tip of cavity.
-LiAl at low temperaturesSugai, Hiroyuki; Yahagi, Masahito*; Kuriyama, Kazuo*; Maeta, H.*
JAERI-Conf 99-013, p.204 - 206, 2000/01
no abstracts in English
Sugai, Hiroyuki
JAERI-Research 99-041, 164 Pages, 1999/07
JAERI-Research-99-041.pdf:6.7MB
no abstracts in English
Kawasuso, Atsuo; Morishita, Norio; Oshima, Takeshi; Okada, Sohei; Ito, Hisayoshi; Yoshikawa, Masahito; Nashiyama, Isamu; Yoshida, Sadafumi*; Okumura, Hajime*
Applied Physics A, 67(2), p.209 - 212, 1998/00
Times Cited Count：42 Percentile：82.87(Materials Science, Multidisciplinary)no abstracts in English
Kawasuso, Atsuo
Hoshasen, 24(3), p.21 - 28, 1998/00
no abstracts in English
Kawasuso, Atsuo; Ito, Hisayoshi; Okada, Sohei; D.Cha*
Mater. Sci. Forum, 264-268, p.611 - 614, 1998/00
no abstracts in English
Kawasuso, Atsuo; Ito, Hisayoshi; Abe, Koji*; Okada, Sohei; Oshima, Takeshi
Journal of Applied Physics, 82(7), p.3232 - 3238, 1997/10
Times Cited Count：24 Percentile：73.69(Physics, Applied)no abstracts in English
Ge
bulk crystalsKawasuso, Atsuo; Okada, Sohei; *; *; *
Journal of Applied Physics, 81(6), p.2916 - 2918, 1997/03
Times Cited Count：4 Percentile：28(Physics, Applied)no abstracts in English
