JOPSS - Search Results

Journal Articles

Defect layer in SiO-SiC interface proved by a slow positron beam

Maekawa, Masaki; Kawasuso, Atsuo; Yoshikawa, Masahito; Miyashita, Atsumi; Suzuki, Ryoichi*; Odaira, Toshiyuki*

Physica B; Condensed Matter, 376-377, p.354 - 357, 2006/04

https://doi.org/10.1016/j.physb.2005.12.091

Times Cited Count：2 Percentile：12.56(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Interaction of nitrogen with vacancy defects in N $^{+}$ -implanted ZnO studied using a slow positron beam

Chen, Z. Q.; Maekawa, Masaki; Kawasuso, Atsuo; Suzuki, Ryoichi*; Odaira, Toshiyuki*

Applied Physics Letters, 87(9), p.091910_1 - 091910_3, 2005/08

https://doi.org/10.1063/1.2037847

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 800 $^{circ}$ C as compared to their full recovery in the O-implanted sample, suggesting a strong interaction between nitrogen and vacancy clusters. At 1000-1100 $^{circ}$ C, nitrogen also forms stable complexes with thermally generated vacancies. To remove all the detectable vacancy defects, a high temperature annealing at 1250 $^{circ}$ C 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 800 $^{circ}$ C. 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.

Journal Articles

Structural defects in SiO/SiC interface probed by a slow positron beam

Maekawa, Masaki; Kawasuso, Atsuo; Chen, Z. Q.; Yoshikawa, Masahito; Suzuki, Ryoichi*; Odaira, Toshiyuki*

Applied Surface Science, 244(1-4), p.322 - 325, 2005/05

https://doi.org/10.1016/j.apsusc.2004.10.085

Times Cited Count：13 Percentile：49.91(Chemistry, Physical)

no abstracts in English

Journal Articles

Microvoid formation in hydrogen-implanted ZnO probed by a slow positron beam

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

https://doi.org/10.1103/PhysRevB.71.115213

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 $^{15}$ cm $^{-2}$ . Positron annihilation measurements show introduction of zinc vacancies, which are filled with hydrogen atoms. After isochronal annealing at 200-500 $^{circ}$ C, the vacancies agglomerate into hydrogen bubbles. Further annealing at 600-700 $^{circ}$ C causes release of hydrogen out of the bubbles, leaving large amount of microvoids. These microvoids are annealed out at high temperature of 1000 $^{circ}$ 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.

Journal Articles

Production and recovery of defects in phosphorus-implanted ZnO

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

https://doi.org/10.1063/1.1821636

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 $^{13}$ -10 $^{15}$ cm $^{-2}$ . Positron annihilation measurements show the introduction of vacancy clusters after implantation. These vacancy clusters evolve to microvoids after annealing at a temperature of 600 $^{circ}$ C, and disappear gradually up to 1100 $^{circ}$ C. Raman scattering measurements show the production of oxygen vacancies (V $_{O}$ ). They are annealed up to 700 $^{circ}$ C 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 600 $^{circ}$ C. 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.

Journal Articles

Evolution of voids in Al-implanted ZnO probed by a slow positron beam

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

https://doi.org/10.1103/PhysRevB.69.035210

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 $^{14}$ Al/cm the implanted layer is amorphized. Heat treatment up to 600 $^{circ}$ 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 $^{circ}$ C. Afterwards, implanted Al impurities are completely activated to contribute the n-type conduction. The ZnO crystal quality is also improved after recrystallization.