Dynamic hydrogen isotope behavior and its helium irradiation effect in SiC. Yasuhisa Oya and Satoru Tanaka The University of Tokyo. Objective. Structural materials for future fusion reactor. Thermal and chemical stability. SiC/SiC Composite Low activation Ferritic steel Vanadium alloy.
Yasuhisa Oya and Satoru Tanaka
The University of Tokyo
Structural materials for future fusion reactor
Thermal and chemical stability
Low activation Ferritic steel
From the viewpoint of fusion safety
Understanding of hot atom behavior of hydrogen isotopes
in fusion reactor circumstance
（Under high energy particles irradiation circumstance ）
Evaluation of Hydrogen isotope retention behavior and chemical states of SiC by D2+-He+ irradiation by X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS)
Annealing at 1300K for 10 minutes under the vacuum less than 10-8Pa
Energy: 1.0 keV
Flux : 1.3 x 1018 D+m-2s-1
Fluence : 1.0x1022 D+ m-2
Energy : 1.3 keV
Flux : 1.3 x 1018 D+m-2s-1
Fluence : 0-1.0x1022 D+ m-2
(Thermal desorption spectroscopy)
(X-ray photoelectron spectroscopy)
X-ray source : Mg-Kα
Heating rate : 0.5 K s-1
Temperature : 300-1300 K
ROICERAM-HSAsahi Glass Co. Ltd.
Polycrystalline -SiC(3C-SiC) : Ф10mm×1mmdensity : 3.10 g/cm3
The sample can be transferred between TDS chamber and XPS chamber without air exposure.
XPS measurements were performed at room temperature.
Thermal desorption spectra of D2 from SiC
Two D2 desorption stages
1st stage at 800 K
2nd stage at 1000 K
(Deuterium bound to Si)
(Deuterium bound to C)
D trapping states in SiC : Si-D, C-D
D and He retention as a function of He+ fluence
D2 TDS spectra after D2+ irradiation with various ion fluence
D retention decreased by He+ pre-irradiation.
D retention was not changed by He+ pre-irradiation above the fluence of 0.1 x 1022 He+m-2.
D is trapped by Si after saturation of C-D bonds.
Si-D is a major chemical state in SiC.
(a) C 1s
(b) Si 2p
By heating above 800 K, the peak position of C 1s was shifted to lower energy side, although that of Si 2p was almost remained in the lower energy side.
Both peaks were recovered by heating about 1200 K.
Summary of peak positions by heating
Implantation temperature dependence on deuterium retention in SiC
Comparison of deuterium retention in SiC and graphite
By heating the sample at 573 K, the deuterium retention was decreased less than half.
However, the deuterium retention was found even above 913 K.
(1.0×1022 He+ m-2)
Only D2+ irradiation
D2 desorption mainly consists of two stages.
D trapped by Si decreased by He+ post irradiation.
Sensitivity of XPS
C 1s : C-D bond
Si 2p : mainly defects
By D2+ irradiation,
C 1s : High energy side
Si 2p : Low energy side
By He+ irradiation,
C 1s : Slight shift toward lower energy side
Si 2p : Shift toward lower energy side
D was trapped by SiC and some defects would be also introduced.
By He+ irradiation,more damaged structures were introduced.
By heating, C 1s was shifted toward low energy side and Si 2p was moved toward high energy side.
After the dissociation of C-D bond, the damaged structures would be recovered.
Above 1200K, both of C1s and Si2p were shifted to higher energy side.
Peak positions of C 1s and Si 2p as a function of heating temperature
XPS spectra of C 1s after heating at 1300K
By heating, D was detrapped and SiC structure would be recovered, which led to decrease FWHM.
Above 1000K, C was aggregated on the surface and form C=C and/or C-C bonds, which contribute to increase FWHM.
Binding Energy / eV
Binding Energy /eVXPS spectra after heating at 1150 K and 1300 K
Peak top: 284.23 eV, FWHM: 1.93 eV →C-C bond
Peak top: 282.98 eV, FWHM: 1.43 eV →C-Si bond
C was aggregated by heating at 1300 K.
Chemical states of C and Si in SiC after heating 1300 K were evaluated by Ar+ sputtering.
C was aggregated on the surface.
C 1s was largely shifted to lower energy side at the depth of a few nm.
Decrease of C=C and/or C-C bond and only Si-C exists in the bulk of SiC
Si-C bond is a major chemical state at the depth of ～20nm(irradiation range）.
SiC structures were disordered by D2+and He+ irradiation.