Photon Factory Activity Report 2019 #37 (2020)

BL-10C/2012G710

Defect Structure Investigations in Amorphous SiO2 Induced on
Swift Heavy Ions by SAXSSatoru YOSHIOKA1*, Konosuke, TSURUTA1, Yusuke SUEMATSU1, Kazuhiro YASUDA1,
Syo MATSUMURA1 and Norito ISHIKAWA2
1Department of Applied Quantum Physics and Nuclear Engineering, Faculty of Engineering
Kyushu University,
744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
2Nuclear Science and Engineering Center, Japan Atomic Energy Agency,
2-4 Oaza-shirakata, Tokai-mura, Ibaraki, 319-1195, Japan
1 Introduction
Radiations such as neutron, x-ray, swift heavy ions andetc. interact with materials and cause structural changes.
They are, therefore, applied to material processing,modifications and etc. Swift heavy ion (SHI) irradiation
provides high energy deposition through electronic
stopping to the materials. SHIs in insulating solid materials
can leave trails of damage with diameters of several
nanometers along the ion path, so called ion tracks. The
defect structures in crystalline materials were detected as
lattice mismatches by diffraction techniques, especiallyusing transmission electron microscopy (TEM). On theother hand, for amorphous materials, subtle densitychanges between track and matrix material are required tobe observed. Tracks in amorphous SiO2 are attracting
attention due to its applications in a wide range of fields.
In this study, we investigated ion track shapes inamorphous SiO2 induced on SHI irradiation using small
angle x-ray scattering (SAXS).
2 Experiment
Silica glass (a-SiO2) plate (ATOCK Co., Ltd) wereirradiated with 100 MeV Kr ions to fluence of 3×1011 cm-2
at H1 beamline of the Tandem ion accelerator facility inJapan Atomic Energy Agency (JAEA)-Tokai. The
irradiation experiment was performed at room temperature
in a vacuum. The sample thickness was 100 m forsufficient X-ray transmittance in SAXS measurements andthe penetration depth of injected Xe ions was estimatedwithin 20 m by SRIM code [1]. For the given fluence
range, track overlap was negligible. The SAXS
measurements were carried out at BL-6A in KEK-PF,
Japan using an X-ray wavelength of 1.5 Å (8.27 keV) anda camera length of 1.0 m. Images were taken intransmission geometry using a two-dimensional pixelarray detector (PILATUS-300K-W, DECTRIS) with an
exposure time of 600 s. Unirradiated SiO2 specimen wasalso measured as a standard for background removal.
3 Results and Discussion
Figure 1 shows SAXS images of an a-SiO2 specimen
irradiated with 100 MeV Kr ions to a fluence of 3×1011 cm2. Radial symmetrical image was observed at the X-ray
beam incident parallel to the direction of SHI irradiation asshown in Fig. 1 (a). On the other hand, streaks are apparent
in the images on tilting geometry between the sample
surface and the X-ray (Fig. 1(b-d)). The width andcurvature of streaks are clearly observed to be narrowerand smaller, respectively, with increasing of the tilting
angle. These image behaviors dependent on the tilting
conditions are due to elongated cylinder-shape scattering
substances, which have thin disc-shape in reciprocal space[2]. Previous study of a-SiO2 irradiated with 89 MeV Au
has observed similar SAXS image behavior [3]. Detailed
track shapes are currently under analysis assuming ahomogenous cylindrical model.
(a) 0°(b) 2°(c) 5°(d) 10°

Fig. 1: SAXS images of SiO2 irradiated with 100 MeV Krto a fluence of 3 ×1011 ions/cm2. (a) The sample was set
with the X-ray beam incident parallel to the direction ofSHI irradiation. (b-d) The sample was tilted to 2°, 5°, 10°,respectively with respect to the X-ray beam. The central
spot without intensities in each image is the catcher for theincident X-ray beam.
References[1] J.F. Ziegler et al., The Stopping and Range of Ions inSolids, Pergamon, New York, (1985).
[2] D. Albrecht et al., App. Phys. A 37, 37-46 (1985).
[3] P. Kluth et al., Nucl. Instr. and Meth. B, 266, 2994-2997(2008)* syoshioka@nucl.kyushu-u.ac.jp