Surface effect on ion track formation in amorphous SiN films

Morita, Yosuke*; Nakajima, Kaoru*; Suzuki, Motofumi*; Narumi, Kazumasa; Saito, Yuichi; Ishikawa, Norito; Hojo, Kiichi; Tsujimoto, Masahiko*; Isoda, Shoji*; Kimura, Kenji*

Nuclear Instruments and Methods in Physics Research B, 315, p.142 - 145, 2013/11

https://doi.org/10.1016/j.nimb.2013.03.043

Fabrication of highly-oriented silicide film on Si substrate treated by low-energy ion beam

Hamamoto, Satoshi*; Yamaguchi, Kenji; Hojo, Kiichi

Transactions of the Materials Research Society of Japan, 38(1), p.89 - 92, 2013/03

https://doi.org/10.14723/tmrsj.38.89

Application of sputter etching treatment to the formation of semiconducting silicide film on Si substrate

Yamaguchi, Kenji; Esaka, Fumitaka; Sasase, Masato*; Yamamoto, Hiroyuki; Hojo, Kiichi

Transactions of the Materials Research Society of Japan, 37(2), p.245 - 250, 2012/06

https://doi.org/10.14723/tmrsj.37.245

"Semiconducting silicides", such as -FeSi, BaSi, MgSi, etc. are composed of elements which are non or less toxic and are naturally abundant, so that they are considered to be ecologically friendly. These materials are being investigated for applications in optoelectronics, photovoltaics, photonics, thermoelectrics, and so on. In order to fabricate silicide films on crystalline Si substrate, sputter-etching (SE) of the substrate with low energy ion beams has been successfully applied. When the conditions are met, a highly-oriented -FeSi (100) film can be grown on Si (100) substrate by means of ion beam sputter deposition method. According to cross-sectional transmission electron microscopy (TEM) observation, the interface of the SE-treated substrate and the film deposited at 973 K is smooth, although some defects are produced as a result of this treatment. On the other hand, a combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) revealed that relatively homogeneous -FeSi surface is formed at this temperature. In order to further improve the film properties with smaller amount of defects, SE-treatment is performed with the ions whose incident energy is below 1 keV. X-ray diffraction (XRD) analysis confirmed that highly-oriented -FeSi (100) film can be also obtained with SE-treatment by 0.8 keV Ne ions, as in the case of 3.0 keV Ne.

Alpha-ray detection with a MgB transition edge sensor

Okayasu, Satoru; Katagiri, Masaki; Hojo, Kiichi; Morii, Yukio; Miki, Shigenobu*; Shimakage, Hisashi*; Wang, Z.*; Ishida, Takekazu*

Physica C, 468(15-20), p.1998 - 2000, 2008/09

https://doi.org/10.1016/j.physc.2008.05.114

We have been investigating for neutron detection with the MgB transition edge sensor (TES). For the purpose, we have been developing a low noise measurement system for neutron detection. To confirm the usefulness of our detecting system, alpha-ray detection from an Am source was achieved. To improve the sensitivity, short meander samples with 35 m length and 1 m width is used. Samples are fabricated by the Kansai group. Superconducting transition temperature Tc is 23.3 K. The transition width is sharp enough less than 1 K. The detection was achieved under a constant current condition, and the resistivity changes at the sample due to the alpha-ray irradiation were detected. The bias current is 6 A.

Local neutron transmutation doping using isotopically enriched silicon film

Yamada, Yoichi; Yamamoto, Hiroyuki; Oba, Hironori; Sasase, Masato*; Esaka, Fumitaka; Yamaguchi, Kenji; Udono, Haruhiko*; Shamoto, Shinichi; Yokoyama, Atsushi; Hojo, Kiichi

Journal of Physics and Chemistry of Solids, 68(11), p.2204 - 2208, 2007/11

https://doi.org/10.1016/j.jpcs.2007.08.056

Si in natural Si has been widely used for a doping source, since Si can be transmuted into P by thermal neutron (Neutron Transmutation Doping, NTD). NTD of nanostructure fabricated from Si-enriched materials can serve as a controlled local doping method with tunable dopant concentration, which cannot be realized by conventional doping methods such as ion implantation. In the present study, Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using Si-enriched SiF as the source gases. The film contains 7.1 % of Si, which is twice higher than that of natural Si. Possible contaminant, fluorine, is lower than 0.6 at.% determined from X-ray photoelectron spectra. Nanostructure of films and changes of electronic properties by the neutron irradiation will also be discussed.

Crystal nucleation behavior caused by annealing of SiC irradiated with Ne at liquid nitrogen temperature or at 573K

Aihara, Jun; Hojo, Kiichi; Furuno, Shigemi*; Hojo, Tomohiro; Sawa, Kazuhiro; Yamamoto, Hiroyuki; Motohashi, Yoshinobu*

Materials Transactions, 48(7), p.1896 - 1900, 2007/07

https://doi.org/10.2320/matertrans.MRA2007608

Silicon carbide(SiC) TEM specimens were annealed, in-situ, at 1273K for 30 minutes after amorphization with 30keV Ne irradiation to the fluence of 1.9 or 2.310Ne/m at 573K or about 98K. The crystal nucleation and bubble coalescence accompanied by recrystallization were observed in both specimens with the annealing after the irradiations. 2.310Ne/m irradiations in both specimens. The Debye-Sherrer rings of the nucleated crystals well fitted the net pattern of the matrix, even though no ring corresponding to (200) of -SiC appeared. Dependence of the crystal nucleation behavior on irradiation temperature was not observed within the present experimental range.

Structure of beam tracks induced by swift heavy ions in BiSrCaCuO superconductors

Sasase, Masato*; Okayasu, Satoru; Yamamoto, Hiroyuki; Kurata, Hiroki*; Hojo, Kiichi

Japanese Journal of Applied Physics, Part 1, 46(2), p.783 - 786, 2007/02

https://doi.org/10.1143/JJAP.46.783

Columnar defects are produced in semiconductor and insulator materials by swift heavy ion irradiation. It has been considered that the electronic stopping power of irradiating ions is the dominant factor in the formation of defects. However, our recent results suggest that ion-velocity is also an important parameter for use in describing this phenomenon. We investigate the columnar defects produced in BiSrCaCuO (Bi-2212) superconductor by heavy ion irradiation (Au, I, Br, and Ni) in the energy range of 60-600MeV. From tansmission electron microscopy, it is shown that the diameters of columnar defects become smaller and their distribution become narrower with an increase in ion velocity. This is explained as an effect of nuclear collision by calculation of the mean free path for the irradiated ions. The present results imply that nuclear collisions strongly affect the formation of columnar defects, even for swift heavy ion irradiation.

Loop formation by ion irradiation in yttria stabilized zirconia

Hojo, Tomohiro*; Yamamoto, Hiroyuki; Aihara, Jun; Furuno, Shigemi*; Sawa, Kazuhiro; Sakuma, Takashi*; Hojo, Kiichi

Nuclear Instruments and Methods in Physics Research B, 250(1-2), p.101 - 105, 2006/09

https://doi.org/10.1016/j.nimb.2006.04.093

Yttria stabilized zirconia (YSZ) is a candidate material focused as optical and insulating materials in nuclear reactors. Therefore, it is useful to investigate defect formation during irradiation, in order to assess YSZ resistance to radiation damage. In the present study, in situ transmission electron microscopy (TEM) observations were performed on YSZ during 30 keV Ne irradiation in the temperature range of 723-1123 K. For irradiations below 1023 K, defect clusters and bubbles were formed simultaneously. On the other hand, at 1123 K, only bubbles were formed in the initial stage of irradiation. Loops formed later following the bubble formation. It was also observed that, in the early stage of irradiation above 923 K, larger bubbles were formed along the loop planes compared with other areas. TEM observations indicated that dislocation loops formed on three kinds of crystallographic planes: namely, (100), (111) and (112) planes.

Cross-sectional transmission electron microscopy of interface structure of -FeSi/Si(100) prepared by ion beam sputter deposition

Sasase, Masato*; Shimura, Kenichiro*; Yamamoto, Hiroyuki; Yamaguchi, Kenji; Shamoto, Shinichi; Hojo, Kiichi

Japanese Journal of Applied Physics, Part 1, 45(6A), p.4929 - 4933, 2006/06

https://doi.org/10.1143/JJAP.45.4929

no abstracts in English

Local oxidation induced by inhomogeneous stress on blistered Si surface

Igarashi, Shinichi*; Itakura, Akiko*; Kitajima, Masahiro*; Nakano, Shinsuke*; Muto, Shunsuke*; Tanabe, Tetsuo*; Yamamoto, Hiroyuki; Hojo, Kiichi

Japanese Journal of Applied Physics, Part 1, 45(5A), p.4179 - 4182, 2006/05

https://doi.org/10.1143/JJAP.45.4179

By utilizing surface stress to modify surface reaction potential and increase surface reactivity, a technique for the twodimensional patterning of surface chemical reactions may be realized by surface stress modulation. A blister is a local protrusion on a solid surface induced by gas ion irradiation, and is considered to create local stress on surface layers. Si(100) substrate was irradiated with H (incident energy: 10 keV, fluence: 110 ions) at an angle of 30 to the surface normal. Blisters of 1-5 mm in diameter at the base were formed. After the ion irradiation, the substrate was oxidized. Scanning Auger electron microscopy revealed that, compared with the flat surface, the perimeters of the blisters had a higher oxygen intensity whereas the blister tops had a lower oxygen intensity. The stress distribution of the blister was calculated using the finite element method. It was found that the surface layers were stretched laterally at the blisters tops and compressed at theperimeters, relative to the flat surface. There was a clear correspondence between the O distribution and the stress distribution on the surface. Our results indicate that the patterned oxidation of the Si surface can be governed by the application of surface stress.