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1-10 Hole Concentration [cm -3 ] 10 15 Mechanisms of Changes of Hole Concentration in Al-doped 6H-SiC by Electron Irradiation and Annealing H. Matsuura a) , H. Yanagisawa a) , K. Nishino a) , Y. Myojin a) , T. Nojiri a) , Y. Matsuyama a) , S. Onoda b) and T. Ohshima b) a) Dept. of Electric and Electronic Engineering, Osaka Electro-Communication University, b) Environment and Industrial Materials Research Division, QuBS, JAEA By comparing electron-radiation damage in p-type 4H-SiC with that in p-type Si, 1, 2) it was found that the reduction in the temperature-dependent hole concentration p(T) in Al-doped p-type 4H-SiC by electron irradiation was much larger than in Al-doped p-type Si. From p(T) for lightly Al-doped 6H-SiC epilayers, an acceptor species with E V+0.2 eV, which is ascribed to an Al atom at a Si sublattice site, was observed. In heavily Al-implanted p-type 6H-SiC layers, the removal cross section of Al acceptors (κ Al) for 1 MeV electron irradiation was determined to be 6.4 × 10-18 cm 2, 3) . A 4.9 μm-thick lightly Al-doped p-type 6H-SiC epilayer on n-type 6H-SiC (resistivity: 0.027 Ωcm) was cut to a 1 × 1 cm2 size. The sample was irradiated with 200 keV electrons with total fluences (Φ) of 0, 1.0, 2.0, and 3.0 × 10 16 cm -2 at room temperature. The value of p(T) were obtained by Hall-effect measurements. Since the p(T) at Φ of 3.0 × 1016 cm -2 could not be obtained, the sample was annealed at 500 °C for 2 min in an Ar atmosphere. The densities and energy levels of acceptors were determined by free carrier concentration spectroscopy (FCCS) 1-4) from p(T). Figure 1 shows the experimental p(T) before irradiation (○) and after irradiation with 200 keV electrons with Φ of 1.0 × 1016 cm -2 (▲) and 2.0 × 1016 cm -2 (□). The value of p(T) in the annealed sample is denoted by + in Fig. 1. Using p(T), the densities (N Al and N DA) and levels (E Al and E DA) of Al and deep acceptors were determined by FCCS. 200 keV electrons Fluence [cm -2 ] : 0 : 1x10 16 : 2x10 16 : 3x10 16 and 500 o C annealing for 2 min 1000/T [K -1 10 1 2 3 4 5 ] 13 10 14 Fig. 1 Temperature dependence of hole concentration for Al-doped p-type 6H-SiC before and after irradiation with three difference Φ of 200 keV electrons. The p(T) for the annealed sample was shown by +. The solid lines represent p(T) simulations with N Al, E Al, N DA, E DA, and N comp obtained by FCCS. JAEA-Review 2010-065 - 14 - Since each p(T) simulation (solid line) with the obtained values is in good agreement with the corresponding experimental p(T), the values obtained by FCCS are reliable. Figure 2 shows the dependence of N Al and N DA on Φ, denoted by ○ and Δ, respectively. At Φ of 3.0 × 1016 cm -2 , N Al and N DA in the 500 °C-annealed sample were shown by ● and ▲, respectively. Although N Al and N DA in the sample irradiated with Φ of 3 × 1016 cm -2 could not be determined, they are expected to be 4.3 × 1013 and 2.1 × 1015 cm -3 , respectively, by simulation 4) with κ Al of 1 × 10-16 cm 2 and κ DA of 9 × 10-18 cm 2 . The simulations of the dependence of N Al and N DA on Φ represent the solid and broken lines in Fig. 2, respectively. After annealing the sample at 500 °C for 2 min, N Al and N DA could be determined to be 4.0 × 1014 and 1.5 × 10 15 cm -3 , respectively. By annealing at 500 °C, N Al is increased, and N DA is decreased. From Fig. 2, furthermore, the increment of N Al is nearly equal to the decrement of N DA. These suggest that the 500 °C annealing transforms the deep acceptors into the Al acceptors. References 1) H. Matsuura et al., Jpn. J. Appl. Phys. 45 (2006) 2648. 2) H. Matsuura et al., Physica B 376-377 (2006) 342. 3) H. Matsuura et al., Jpn. J. Appl. Phys. 47 (2008) 5355. 4) H. Matsuura et al., J. Appl. Phys 104 (2008) 043702. Density [x10 15 cm -3 ] 3 2 1 N A2 N A1 After 773 K annealing for 2 min Fluence of 200 keV electrons [x10 16 cm -2 0 1 2 3 ] Fig. 2 Dependence of N Al and N DA on Φ of 200 keV electrons. Since NAl and N DA in the sample irradiated at Φ of 3 × 1016 cm -2 could not be obtained, the sample was annealed at 500 °C for 2 min. N Al and N DA in the annealed sample are denoted by ● and ▲, respectively. The dependence of N Al and N DA on Φ, simulated with κ Al of 1 × 10-16 cm 2 and κ DA of 9 × 10 -18 cm 2 , are shown by solid and broken lines, respectively.
Hydrogen Diffusion in a-Si:H Thin Films due to High Temperature Ion Irradiation S. Sato a) , T. Ohshima a) and M. Imaizumi b) a) Environment and Industrial Materials Research Division, QuBS, JAEA, b) Aerospace R&D Directorate, JAXA I. Introduction Thin film hydrogenated amorphous silicon (a-Si:H) solar cells are one of major candidates for ‘flexible’ space solar cells, and thus studies of radiation effect on a-Si:H thin films are very important for the space applications 1) . However, radiation effects on electrical properties of a-Si:H semiconductors are less understood compared to crystalline type semiconductors such as silicon, gallium arsenide, and so on. In this context, our group have been studying about radiation effects on a-Si:H thin films, especially focusing on 2) the electrical properties and the hydrogen diffusion behavior. Hydrogen diffusion and emission rates in a-Si:H depend on the hydrogen bonding state. Clustered (not isolated) hydrogen atoms are relatively easily diffuse or emit in 3) amorphous network compared to isolated hydrogen atom . Since it is well known that clustered hydrogen atoms deteriorate the electrical properties of a-Si:H thin films, it may be possible to evaluate a change in the electrical properties by investigating the hydrogen behavior due to irradiation. The aim of this study is to observe hydrogen diffusion in ion-irradiated a-Si:H thin films with varying temperatures. Previously, we developed the in-situ Elastic Recoiled Detection (ERD) system following ion irradiation at low temperature condition in the dual beam irradiation chamber 4) (MD2) . Since the chamber connected to both the 400 kV Ion Implanter and from the 3 MV Single-Ended Accelerator, ERD measurement using beams from the former one can be Hydrogen Content [Arb.Units] 1-11 Initial (523 K) 330 keV Si, 1x10 16 /cm 2 (523 K) 330 keV Si, 1x10 16 /cm 2 (613 K) 800 600 400 200 0 Depth [nm] Fig. 1 ERD spectrum of an a-Si:H thin film before and after 330 keV Si ion irradiation at 1.0 × 1016 /cm 2 at 523 K. The sample temperature was raised to 613 K after the irradiation. No significant hydrogen diffusion was observed in this condition. JAEA-Review 2010-065 - 15 - performed for a sample just after the ion irradiation (implantation) from the latter one. In this study, we have additionally installed a sample heating system for irradiation under elevated temperature, and have observed hydrogen behavior in a-Si:H thin films irradiated with Si ions. II. Experimental The samples used in this study were device grade a-Si:H thin films fabricated on crystalline silicon (c-Si) substrates by Plasma Enhanced Chemical Vapor Deposition (PECVD) at National Institute of Advanced Industrial Science and Technology (AIST). The thickness of the a-Si:H thin film and the hydrogen content were estimated to be 300 nm and 11.3 at%, respectively. Figure 1 shows the results of the ERD measurements before and after 330 keV Si ion irradiation at the fluence of 1.0 × 1016 /cm 2 . The incident beam angle was 55 o from the sample plane. It was expected from the TRIM calculation that Si ions were implanted in the vicinity of the a-Si:H/c-Si interface and the average displacement per atom in the film was 12 dpa. The sample temperature was kept at 523 K during the irradiation for 4.5 hours. Elastic recoiled detection measurement after the irradiation was also carried out at 523 K. No specific change of the hydrogen distribution was observed between before and after the irradiation. The sample temperature was increased to 613 K after the irradiation and the ERD measurement was carried out again. However, no significant hydrogen diffusion was still observed. The result indicates that the hydrogen diffusion was under the detection limit even if it was enhanced due to the ion irradiation and that the samples used in this study were high quality films for electric device use. Higher temperature or longer annealing time is needed in order to observe the hydrogen diffusion. Finally, we would like to thank Hitoshi Sai of AIST for fabricating the a-Si:H samples. References 1) N. Wyrsch et al., J. Non-Cryst. Solids 352 (2006) 1797-1800. 2) S. Sato et al., Proc. 34th IEEE PVSC, (2009) 002354-002358. 3) X.-M. Tang et al., Solid State Commun. 74 (1990) 171-174. 4) S. Sato et al., JAEA Takasaki Ann. Rep. 2008 (2009) 11.
Page 3 and 4: JAEA-Review 2010-065 JAEA Takasaki
Page 5 and 6: JAEA-Review 2010-065 PREFACE This r
Page 7: JAEA-Review 2010-065 and pulsed hea
Page 10 and 11: JAEA-Review 2010-065 1-23 Studies o
Page 12 and 13: JAEA-Review 2010-065 3-24 Lethal Ef
Page 14 and 15: JAEA-Review 2010-065 4-07 Fabricati
Page 16 and 17: JAEA-Review 2010-065 5. Status of I
Page 18 and 19: JAEA-Review 2010-065 1-13 Alpha-rad
Page 21 and 22: 1-01 Radiation Resistance of InGaP/
Page 23 and 24: 1-03 Evaluation of Soft Error Rates
Page 25 and 26: 1-05 Heavy-ion Induced Current in S
Page 27 and 28: Total Ionizing Dose Tolerance of Si
Page 29: 1-09 Evaluation of Single Event Eff
Page 33 and 34: 1-13 Alpha-radiolysis of Organic Ex
Page 35 and 36: Study on Stability of Cs·Sr Solven
Page 37 and 38: Irradiation Effect of Gamma-Rays on
Page 39 and 40: 1-19 Development of Radiation Resis
Page 41 and 42: 1-21 Alpha-Ray Irradiation Damage o
Page 43 and 44: 1-23 Studies on Microstructure and
Page 45 and 46: 1-25 Effect of Groundwater Radiolys
Page 47 and 48: 1-27 Simulation of Neutron Damage M
Page 49 and 50: 1-29 Irradiation Hardening in Ion-i
Page 51 and 52: 1-31 Preparation of Anion-Exchange
Page 53 and 54: 1-33 Radiation-Induced Graft Polyme
Page 55: JAEA-Review 2010-065 2. Environment
Page 58 and 59: 2-02 Development of Zwitterionic Mo
Page 60 and 61: Modification of Hydroxypropyl Cellu
Page 62 and 63: The Recovery of Precious Metals Usi
Page 64 and 65: 2-08 ESR Study on Carboxymethyl Chi
Page 67 and 68: JAEA-Review 2010-065 3. Biotechnolo
Page 69 and 70: JAEA-Review 2010-065 3-28 Electron
Page 71: JAEA-Review 2010-065 3-51 PET Studi
Page 74 and 75: 3-02 Mutagenic effects of He ion pa
Page 76 and 77: 3-04 Functional Analysis of Flavono
Page 78 and 79: 3-06 Generation New Ornamental Plan
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3-08 Stability of Flower-colour Mut
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3-10 JAEA-Review 2010-065 Effects o
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3-12 Producing New Gene Resources i
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3-14 Production of Soybean Mutants
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Assessment of Irradiation Treatment
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3-18 Effect of Different LET Radiat
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3-20 JAEA-Review 2010-065 Fungicide
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3-22 JAEA-Review 2010-065 FACS-base
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3-24 Lethal Effects of Different LE
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3-26 JAEA-Review 2010-065 Ion Beam
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3-28 Electron Spin Relaxation Behav
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3-30 Target Irradiation of Individu
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3-32 Carbon-ion Microbeam Induces B
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3-34 Biological Effects of Carbon I
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3-36 Difference in Bystander Lethal
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3-38 Analysis of Lethal Effect Medi
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3-40 Irradiation with Carbon Ion Be
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3-42 Expression of Two Gelsolins in
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3-44 Analysis of Bystander Cell Sig
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3-46 Quantitative Evaluation of Ric
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3-48 Visualization of 107 Cd Accumu
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3-50 Uniformity Measurement of Newl
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3-52 Imaging and Biodistribution of
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3-54 Improvement of Spatial Resolut
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3-56 The Optimum Conditions in the
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3-58 Evaluation of Cisplatin Concen
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3-60 JAEA-Review 2010-065 Analysis
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3-62 JAEA-Review 2010-065 Sensitivi
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JAEA-Review 2010-065 4-14 The Effec
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JAEA-Review 2010-065 4-39 Relations
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4-01 Hydrogen Gasochromism of WO3 F
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4-03 Synthesis of Single-Crystallin
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4-05 Synergy Effects in Electron/Io
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Fabrication of Diluted Magnetic Sem
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4-09 Gas Permeation Characteristics
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4-11 Control of Radial Size of Poly
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4-13 Behavior of N Atoms in Nitridi
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4-15 JAEA-Review 2010-065 Annealing
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Low Temperature Ion Channeling of F
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4-19 Radiation-Induced Electrical D
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4-21 Study on Cu Precipitation in E
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4-23 Evaluation of Fluorescence Mat
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4-25 Evaluation of the ZrC Layer fo
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4-27 Structure Analysis of K/Si(111
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4-29 LET Effect on the Radiation In
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4-31 Stabilization of Measurement S
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Systematic Measurement of Neutron a
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4-35 Measurement of Neutron Fluence
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4-37 Evaluation of the Response Cha
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4-39 Relationship between Internucl
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4-41 Analysis of Radiation Damage a
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4-43 Positive Secondary Ion Emissio
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4-45 JAEA-Review 2010-065 Ion Induc
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4-47 Fabrication of Dielectrophoret
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4-49 Fast Single-Ion Hit System for
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4-51 Development of Beam Generation
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JAEA-Review 2010-065 5. Status of I
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Operation of the AVF Cyclotron T. N
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Operation of Electron Accelerator a
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5-06 FACILITY USE PROGRAM in Takasa
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5-08 Radioactive Waste Management i
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Appendix 2 List of Related Patents
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Appendix 4 Type of Research Collabo
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表1.SI 基本単位基本量 SI
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