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Maekawa, Masaki; Kawasuso, Atsuo; Yoshikawa, Masahito; Miyashita, Atsumi; Suzuki, Ryoichi*; Odaira, Toshiyuki*
Physica B; Condensed Matter, 376-377, p.354 - 357, 2006/04
Times Cited Count:2 Percentile:12.56(Physics, Condensed Matter)no abstracts in English
Chen, Z. Q.; Maekawa, Masaki; Kawasuso, Atsuo; Suzuki, Ryoichi*; Odaira, Toshiyuki*
Applied Physics Letters, 87(9), p.091910_1 - 091910_3, 2005/08
Times Cited Count:31 Percentile:71.34(Physics, Applied)Zinc oxide crystals were implanted with N, O, and co-implanted with O/N ions. Positron annihilation measurements show the introduction of vacancy clusters upon implantation. In the N-implanted sample, these vacancy clusters are only partially annealed at 800C as compared to their full recovery in the O-implanted sample, suggesting a strong interaction between nitrogen and vacancy clusters. At 1000-1100C, nitrogen also forms stable complexes with thermally generated vacancies. To remove all the detectable vacancy defects, a high temperature annealing at 1250C is needed. Furthermore, Hall measurements of this sample show n-type conductivity though nitrogen is expected as acceptors. On the contrary, in the O/N co-implanted sample, most vacancy clusters disappear at 800C. Probably oxygen scavenges nitrogen to form N-O complexes and hence enhance the annealing of vacancy clusters. A highly compensated semi-insulating layer is formed in the co-implanted sample.
Maekawa, Masaki; Kawasuso, Atsuo; Chen, Z. Q.; Yoshikawa, Masahito; Suzuki, Ryoichi*; Odaira, Toshiyuki*
Applied Surface Science, 244(1-4), p.322 - 325, 2005/05
Times Cited Count:13 Percentile:49.91(Chemistry, Physical)no abstracts in English
Chen, Z. Q.; Kawasuso, Atsuo; Xu, Y.; Naramoto, Hiroshi*; Yuan, X. L.*; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Odaira, Toshiyuki*
Physical Review B, 71(11), p.115213_1 - 115213_8, 2005/03
Times Cited Count:106 Percentile:93.69(Materials Science, Multidisciplinary)ZnO crystals were implanted with 20-80 keV hydrogen ions up to a total dose of 4.410 cm. Positron annihilation measurements show introduction of zinc vacancies, which are filled with hydrogen atoms. After isochronal annealing at 200-500 C, the vacancies agglomerate into hydrogen bubbles. Further annealing at 600-700 C causes release of hydrogen out of the bubbles, leaving large amount of microvoids. These microvoids are annealed out at high temperature of 1000 C. Cathodoluminescence measurements reveal that hydrogen ions also passivate deep level emission centers before their release from the sample, and lead to the improvement of the UV emission.
Chen, Z. Q.; Kawasuso, Atsuo; Xu, Y.; Naramoto, Hiroshi; Yuan, X. L.*; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Odaira, Toshiyuki*
Journal of Applied Physics, 97(1), p.013528_1 - 013528_6, 2005/01
Times Cited Count:147 Percentile:96.37(Physics, Applied)Phosphorus ions were implanted into ZnO crystals with energies of 50-380 keV to a dose of 10-10 cm. Positron annihilation measurements show the introduction of vacancy clusters after implantation. These vacancy clusters evolve to microvoids after annealing at a temperature of 600C, and disappear gradually up to 1100C. Raman scattering measurements show the production of oxygen vacancies (V). They are annealed up to 700C accompanying the agglomeration of vacancy clusters. The light emissions of ZnO are suppressed due to the competing nonradiative recombination centers introduced by implantation. Recovery of the light emission occurs above 600C. The vacancy-type defects detected by positrons might be part of the nonradiative recombination centers. Hall measurement shows n-type conductivity for the P-implanted ZnO layer, which suggests that phosphorus is an amphoteric dopant.
Chen, Z. Q.; Maekawa, Masaki; Yamamoto, Shunya; Kawasuso, Atsuo; Yuan, X. L.*; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Odaira, Toshiyuki*
Physical Review B, 69(3), p.035210_1 - 035210_10, 2004/01
Times Cited Count:91 Percentile:93.47(Materials Science, Multidisciplinary)Introduction and annealing behavior of defects in Al-implanted ZnO have been studied using energy variable slow positron beam. Vacancy clusters are produced after Al-implantation. With increasing ion dose above 10 Al/cm the implanted layer is amorphized. Heat treatment up to 600 C enhances the creation of large voids that allow the positronium formation. The large voids disappear accompanying the recrystallization process by the further heat treatment above 600 C. Afterwards, implanted Al impurities are completely activated to contribute the n-type conduction. The ZnO crystal quality is also improved after recrystallization.
Suzuki, Ryoichi*; *; Uedono, Akira*; Y.K.Cho*; Yoshida, Sadafumi*; Ishida, Yuki*; Oshima, Takeshi; Ito, Hisayoshi; *; Mikado, Tomohisa*; et al.
Japanese Journal of Applied Physics, Part 1, 37(8), p.4636 - 4643, 1998/08
Times Cited Count:28 Percentile:74.39(Physics, Applied)no abstracts in English
Sunaga, Hiromi; Okada, Sohei; Kaneko, Hirohisa; Takizawa, Haruki; Kawasuso, Atsuo; Yotsumoto, Keiichi
NUP-A-96-10, 0, p.95 - 97, 1996/00
no abstracts in English
Okada, Sohei; Kaneko, Hirohisa; Sunaga, Hiromi; *; Takizawa, Haruki; Yotsumoto, Keiichi
Proc. of the 20th Linear Accelerator Meeting in Japan, 0, p.59 - 61, 1995/00
no abstracts in English
Okada, Sohei
Dai-21-Kai Nihon Aisotopu, Hoshasen Sogo Kaigi Rombunshu, p.1 - 13, 1994/02
no abstracts in English
Maekawa, Masaki; Zhou, K.*; Fukaya, Yuki; Zhang, H.; Li, H.; Kawasuso, Atsuo
no journal, ,
no abstracts in English
Wada, Ken*; Maekawa, Masaki; Mochizuki, Izumi*; Shidara, Tetsuo*; Hyodo, Toshio*
no journal, ,
no abstracts in English