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Chen, Z. Q.; Maekawa, Masaki; Kawasuso, Atsuo; Sakai, Seiji; Naramoto, Hiroshi*
JAEA-Review 2005-001, TIARA Annual Report 2004, p.232 - 234, 2006/01
no abstracts in English
-implanted ZnO studied using a slow positron beamChen, 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：71.4(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 800
C 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.
Chen, Z. Q.; Yamamoto, Shunya; Kawasuso, Atsuo; Xu, Y. H.; Sekiguchi, Takashi*
Applied Surface Science, 244(1-4), p.377 - 380, 2005/05
Times Cited Count：16 Percentile：55.78(Chemistry, Physical)Homo- and heteroepitaxial ZnO films were grown by pulsed laser deposition on single crystal ZnO substrate and Al
O
substrate, respectively. The surface roughness probed by atomic force microscope (AFM) depends strongly on the substrate, which is much larger for the heteroepitaxial layer. Doppler broadening of positron annihilation measurements show existence of defects in both of the films, with a higher concentration in the homoepitaxial film. Raman scattering measurements reveal the E2 phonon vibration mode at 437 cm
, which is characteristic of the wurtzite structure. These films show strong ultraviolet (UV) emission at 3.3 eV from the cathodoluminescence measurements, which indicates good optical properties.
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：93.71(Materials Science, Multidisciplinary)ZnO crystals were implanted with 20-80 keV hydrogen ions up to a total dose of 4.4
10
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：96.39(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; Kawasuso, Atsuo; Yamamoto, Shunya; Yuan, X. L.*; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Odaira, Toshiyuki*
JAERI-Review 2004-025, TIARA Annual Report 2003, p.193 - 195, 2004/11
20-80 keV hydrogen ions were implanted into ZnO single crystals up to a total dose of 4.410 cm. Positron annihilation measurements using a slow positron beam revealed introduction of vacancies after implantation, which are filled with hydrogen impurities. After annealing, these hydrogen filled vacancies grow into large hydrogen bubbles. At annealing temperature of 500-700C, these hydrogen impurities are released from the bubbles, and remain open microvoids. These microvoids are finally annealed out at about 1100C. The effects of hydrogen implantation on the light luminescence in ZnO will also be discussed.
ion-implantation-induced defects in ZnO studied with a slow positron beamChen, Z. Q.; Sekiguchi, Takashi*; Yuan, X. L.*; Maekawa, Masaki; Kawasuso, Atsuo
Journal of Physics; Condensed Matter, 16(2), p.S293 - S299, 2004/01
Times Cited Count：25 Percentile：71.56(Physics, Condensed Matter)Undoped ZnO single crystals were implanted with multiple energy N ions ranging from 50 to 380 keV with dose from 10
/cm
to 10
/cm. Positron annihilation measurements show that vacancy defects are introduced in the implanted layers. The concentration of the vacancy defects increases with increasing ion dose. Annealing behavior of the defects can be divided into four stages, which correspond to the formation and recovery of large vacancy clusters, formation and disappearance of vacancy-impurity complexes, respectively. All the implantation induced defects are removed by annealing at 1200C. Cathodoluminescence measurements show that the ion implantation induced defects act as nonradiative recombination centers to suppress the ultraviolet emission. After annealing, these defects disappear gradually and the ultraviolet emission reappears, which coincides with positron annihilation measurement. The Hall measurements reveal that after N-implantation, the ZnO layer still shows n-type conductivity.
-implanted ZnO probed by a slow positron beamChen, 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.
Chen, Z. Q.; Maekawa, Masaki; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Kawasuso, Atsuo
Materials Science Forum, 445-446, p.57 - 59, 2004/00
no abstracts in English
/ZnO films by pulsed laser depositionYamamoto, Shunya; Choi, Y.; Umebayashi, Tsutomu; Yoshikawa, Masahito
Transactions of the Materials Research Society of Japan, 29(6), p.2701 - 2704, 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
H.A.Youssef*; M.M.A.Aziz*; Yoshii, Fumio; Makuuchi, Keizo; A.A.E.Miligy*
Angewandte Makromolekulare Chemie, 218, p.11 - 21, 1994/00
Times Cited Count：7 Percentile：36.28(Polymer Science)no abstracts in English
; ; *; Araki, Kunio
Journal of Polymer Science; Polymer Letters Edition, 13(11), p.677 - 687, 1975/11
no abstracts in English
