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Journal Articles

Non-destructive depth analysis of the surface oxide layer on Mg$$_{2}$$Si with XPS and XAS

Esaka, Fumitaka; Nojima, Takehiro; Udono, Haruhiko*; Magara, Masaaki; Yamamoto, Hiroyuki

Surface and Interface Analysis, 48(7), p.432 - 435, 2016/07

https://doi.org/10.1002/sia.5939
 Times Cited Count：16 Percentile：41.12(Chemistry, Physical)

XPS is widely used for non-destructive chemical state analysis of solid materials. In this method, depth profiling can be carried out by a combination with ion beam sputtering. However, the sputtering often causes segregation and preferential sputtering of atoms and gives inaccurate information. The use of energy-tunable X-rays from synchrotron radiation (SR) enables us to perform non-destructive depth profiling in XPS. Here, the analytical depth can be changed by changing excitation X-ray energy. In the present study, we examined methods to perform depth profiling with XPS by changing excitation energy and XAS by changing electron energy for detection. These methods were then applied to the analysis of native surface oxide layers on Mg$$_{2}$$Si crystals. In this XAS analysis, the peak at 1843.4 eV becomes dominant when the electron energy for detection increases, which implies that Si-O or Si-O-Mg structure is formed as the surface oxide layer on the Mg$$_{2}$$Si.

Journal Articles

Surface structures on $$beta$$-FeSi$$_2$$ formed by heat-treatment in ultra-high vacuum and their influence for homoepitaxial growth

Matsumura, Seidai*; Ochiai, Kunihito*; Udono, Haruhiko*; Esaka, Fumitaka; Yamaguchi, Kenji; Yamamoto, Hiroyuki; Hojo, Kiichi

Physics Procedia, 11, p.174 - 176, 2011/02

https://doi.org/10.1016/j.phpro.2011.01.048
 Times Cited Count：3 Percentile：82.06(Optics)

The surface structures on the surface of $$beta$$-FeSi$$_2$$ substrate after heat treatment in ultra high vacuum and their influence on homoepitaxial growth were investigated. It was found that the dip structures appeared on the surface of $$beta$$-FeSi$$_2$$ (100) substrate after heat treatment above 1023 K, where the evaporation of surface oxide layer (SiO$$_x$$) occurred. The composition of the dip structure was Fe-rich as compared to nominal $$beta$$-FeSi$$_2$$ composition (Si/Fe=2). This result indicates that the decomposition from $$beta$$-FeSi$$_2$$ to $$epsilon$$-FeSi would occur on the surface. The surface morphology observed after heat treatment depended on the orientation of the substrate. In addition, homoepitaxial films with smooth surface on $$beta$$-FeSi$$_2$$ (111) substrate at the growth temperature of 973 and 1073 K were obtained.

Journal Articles

Surface analysis of single-crystalline $$beta$$-FeSi$$_2$$

Yamada, Yoichi*; Mao, W.*; Asaoka, Hidehito; Yamamoto, Hiroyuki; Esaka, Fumitaka; Udono, Haruhiko*; Tsuru, Tomohito

Physics Procedia, 11, p.67 - 70, 2011/02

https://doi.org/10.1016/j.phpro.2011.01.034
 Times Cited Count：3 Percentile：82.06(Optics)

Clean surfaces of the single crystalline $$beta$$-FeSi$$_2$$ have been prepared and investigated. From XPS (X-ray Photoelectron Spectroscopy) measurements of the surface oxide, it is found that the surface Si is mainly oxidized while Fe isn't. After removing the surface oxide, clean surface can be obtained showing reasonable structure in LEED (Low-Energy Electron Diffraction) and STM (Scanning Tunneling Microscope). No drastic surface reconstruction is found reflecting strong Fe-Si bond. DFT (Density Functional Theory) calculation suggests the spin polarized surface DOS (Density Of State) when Fe comes at the surface.

Journal Articles

Surface characterization of homoepitaxial $$beta$$-FeSi$$_{2}$$ film on $$beta$$-FeSi$$_{2}$$(111) substrate by X-ray photoelectron and absorption spectroscopy

Esaka, Fumitaka; Yamamoto, Hiroyuki; Udono, Haruhiko*; Matsubayashi, Nobuyuki*; Yamaguchi, Kenji; Shamoto, Shinichi; Magara, Masaaki; Kimura, Takaumi

Physics Procedia, 11, p.150 - 153, 2011/02

https://doi.org/10.1016/j.phpro.2011.01.043
 Times Cited Count：0 Percentile：0.01(Optics)

Surface characterization of homoepitaxial $$beta$$-FeSi$$_{2}$$ film on $$beta$$-FeSi$$_{2}$$(111) substrate has been performed by X-ray photoelectron and X-ray absorption spectroscopy.

Journal Articles

Spectroscopic characterization of $$beta$$-FeSi$$_{2}$$ single crystals and homoepitaxial $$beta$$-FeSi$$_{2}$$ films by XPS and XAS

Esaka, Fumitaka; Yamamoto, Hiroyuki; Udono, Haruhiko*; Matsubayashi, Nobuyuki*; Yamaguchi, Kenji; Shamoto, Shinichi; Magara, Masaaki; Kimura, Takaumi

Applied Surface Science, 257(7), p.2950 - 2954, 2011/01

https://doi.org/10.1016/j.apsusc.2010.10.097
 Times Cited Count：10 Percentile：41.83(Chemistry, Physical)

Chemical state analysis by a combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is performed for $$beta$$-FeSi$$_{2}$$ single crystals and homoepitaxial $$beta$$-FeSi$$_{2}$$ films. The Si 2p XPS and Fe L-edge XAS spectra imply that the annealing at 1173 K to remove native oxide layers on the crystal induces the formation of FeSi in the surface. The formation of FeSi is also confirmed by Si K-edge XAS analysis. For the homoepitaxial $$beta$$-FeSi$$_{2}$$ films grown on the crystals, the Si K-edge XAS spectra indicate that structurally homogeneous $$beta$$-FeSi$$_{2}$$ films can be grown on the $$beta$$-FeSi$$_{2}$$ single crystals when the substrate temperatures of 973 and 1073 K are applied for molecular beam epitaxy (MBE). Consequently, it is indicated that the combination of XPS and XAS using synchrotron radiation is a useful tool to clarify chemical states nondestructively.

Journal Articles

Surface preparation and characterization of single crystalline $$beta$$-FeSi$$_{2}$$

Yamada, Yoichi; Wakaya, Ippei*; Ouchi, Shinji*; Yamamoto, Hiroyuki; Asaoka, Hidehito; Shamoto, Shinichi; Udono, Haruhiko*

Surface Science, 602(18), p.3006 - 3009, 2008/09

https://doi.org/10.1016/j.susc.2008.07.035
 Times Cited Count：6 Percentile：30.24(Chemistry, Physical)

Well-defined clean surfaces of single crystalline $$beta$$-FeSi$$_{2}$$ have for the first time been prepared and characterized at the atomic scale. Surface oxide was removed by heating the crystal at 850 $$^{circ}$$C in ultra-high vacuum (UHV), resulted in an atomically-flat, clean surface. Scanning tunneling microscope (STM) and low-energy electron diffraction (LEED) measurements reveal the absence of long-range surface reconstruction in the low-index (100), (101) and (110) surfaces, which is unique among compound semiconductors. However a significant number of surface defects could still be found within the clean surface. Characterizing and controlling of those surface defects will be necessary in order to use this material in applications.

Journal Articles

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
 Times Cited Count：6 Percentile：31.20(Chemistry, Multidisciplinary)

$$^{30}$$Si in natural Si has been widely used for a doping source, since $$^{30}$$Si can be transmuted into $$^{31}$$P by thermal neutron (Neutron Transmutation Doping, NTD). NTD of nanostructure fabricated from $$^{30}$$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, $$^{30}$$Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The $$^{30}$$Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using $$^{30}$$Si-enriched SiF$$_{4}$$ as the source gases. The film contains 7.1 % of $$^{30}$$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.

Journal Articles

Novel photosensitive materials for hydrogen generation through photovoltaic electricity

Yamaguchi, Kenji; Udono, Haruhiko*

International Journal of Hydrogen Energy, 32(14), p.2726 - 2729, 2007/09

https://doi.org/10.1016/j.ijhydene.2006.09.014
 Times Cited Count：14 Percentile：36.66(Chemistry, Physical)

no abstracts in English

Journal Articles

Single crystalline $$beta$$-FeSi$$_{2}$$ grown using high-purity FeSi$$_{2}$$ source

Goto, Kohei*; Suzuki, Hirokazu*; Udono, Haruhiko*; Kikuma, Isao*; Esaka, Fumitaka; Uchikoshi, Masahito*; Isshiki, Minoru*

Thin Solid Films, 515(22), p.8263 - 8267, 2007/08

https://doi.org/10.1016/j.tsf.2007.02.066
 Times Cited Count：15 Percentile：55.80(Materials Science, Multidisciplinary)

We have investigated the effect of FeSi$$_{2}$$ source purity on the electrical property of $$beta$$-FeSi$$_{2}$$ grown from solution. A high purity FeSi$$_{2}$$ source avoided a contamination of Cu and W metals was synthesized by melting a high purity Fe (5N) and Si (5N-up) in a quartz ampoule. The $$beta$$-FeSi$$_{2}$$ crystals grown using the high purity FeSi$$_{2}$$ and Zn solvent showed n-type conduction, whereas those grown using the arc-melted FeSi$$_{2}$$ showed p-type. From the SIMS analysis of the grown crystals, we found that dominant impurity concentrations in the p-type crystals were higher than those in the n-type ones.

Journal Articles

Growth of $$beta$$-FeSi$$_2$$ thin films on $$beta$$-FeSi$$_2$$ (110) substrates by molecular beam epitaxy

Muroga, Masataka*; Suzuki, Hirokazu*; Udono, Haruhiko*; Kikuma, Isao*; Zhuravlev, A. V.; Yamaguchi, Kenji; Yamamoto, Hiroyuki; Terai, Takayuki*

Thin Solid Films, 515(22), p.8197 - 8200, 2007/08

https://doi.org/10.1016/j.tsf.2007.02.040
 Times Cited Count：6 Percentile：31.20(Materials Science, Multidisciplinary)

Semiconducting ${it $beta$}$-FeSi$$_2$$ has received much attention as a material for Si-based optoelectronic devices. There are a number of studies on heteroepitaxy of ${it $beta$}$-FeSi$$_2$$ film on Si. However, growth experiments of ${it $beta$}$-FeSi$$_2$$ film on single crystalline ${it $beta$}$-FeSi$$_2$$ substrate have not been investigated yet. Recently, single crystalline ${it $beta$}$-FeSi$$_2$$ with large growth facets by solution growth method using Ga solvent. By obtaining a smooth surface on the substrate, we have succeeded in growing ${it $beta$}$-FeSi$$_2$$ film on ${it $beta$}$-FeSi$$_2$$(110) substrate using molecular-beam epitaxy.

Journal Articles

Effect of thermal annealing on the photoluminescence from $$beta$$-FeSi$$_2$$ films on Si substrate

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

Thin Solid Films, 508(1-2), p.367 - 370, 2006/06

https://doi.org/10.1016/j.tsf.2005.07.354
 Times Cited Count：12 Percentile：49.58(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

Summer Seminar on "Silicide Semiconductors" 2002; August 5-6, 2002, Japan Atomic Energy Research Institute, Tokai Research Establishment

Yamaguchi, Kenji; Yamamoto, Hiroyuki; Hojo, Kiichi; Udono, Haruhiko*

JAERI-Conf 2002-014, 60 Pages, 2003/01

JAERI-Conf-2002-014.pdf:5.35MB

Some silicides are known to be promising as new types of semiconductor, being less hazardous to the environment than conventional compound semiconductors. This seminar was held at Advanced Science Research Center in JAERI (Japan Atomic Energy Research Institute) - Tokai on August 5th and 6th, 2002, where 1 invited lecture, 10 oral and 20 poster presentations were given. It was successfully carried out with the participants reaching as many as 70 people, with plenty of fruitful discussion. This summary is the proceedings of the seminar.

Oral presentation

Surface analysis on single-crystalline $$beta$$-FeSi$$_{2}$$

Mao, W.; Wakaya, Ippei*; Yamada, Yoichi; Esaka, Fumitaka; Yamamoto, Hiroyuki; Shamoto, Shinichi; Yamaguchi, Kenji; Udono, Haruhiko*

no journal, , 

Thin films of semiconducting $$beta$$-FeSi$$_{2}$$ keep attracting considerable attentions for their promising applicability to the Si-based optoelectronics devices. Recently, large single-crystalline $$beta$$-FeSi$$_{2}$$ has successfully been synthesized, providing a substrate for a well-defined homoepitaxy film. As a first step toward good homoepitaxy of $$beta$$-FeSi$$_{2}$$, we prepare and characterize low-index surfaces of $$beta$$-FeSi$$_{2}$$ single crystal. Both LEED and STM reveal the absence of the long-ranged surface reconstruction for each face, which is favorable for the homoepitaxy on this substrate. On the other hand, STM suggests a presence of a significant amount of surface defects for each face, which should be improved in the next step. In addition to structural analysis, the stoichiometry of clean surfaces will be discussed on the basis of XPS and SIMS measurements.

Oral presentation

Surface morphology changes of single crystalline $$beta$$-FeSi$$_2$$ substrate by heat-treatment in ultrahigh vacuum

Ochiai, Kunihito*; Mao, W.; Sekino, Kazuyuki*; Udono, Haruhiko*; Esaka, Fumitaka; Yamaguchi, Kenji

no journal, , 

no abstracts in English

Oral presentation

Surface observation of single crystalline $$beta$$-$${rm FeSi_2}$$

Yamada, Yoichi*; Wakaya, Ippei*; Ouchi, Shinji*; Udono, Haruhiko*; Tsuru, Tomohito; Esaka, Fumitaka; Yamamoto, Hiroyuki

no journal, , 

no abstracts in English

Oral presentation

XPS and XAS analysis of surface chemical states of $$beta$$-FeSi$$_{2}$$ single crystals

Esaka, Fumitaka; Yamamoto, Hiroyuki; Udono, Haruhiko*; Matsubayashi, Nobuyuki*; Yamaguchi, Kenji; Shamoto, Shinichi; Magara, Masaaki; Kimura, Takaumi

no journal, , 

Chemical states of solid surface were investigated by a combination of energy-tunable X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The analysis was performed for the $$alpha$$-phase and $$beta$$-phase iron silicide single crystals. The result reveals that Si-rich and Fe-rich structures exist in the $$alpha$$-phase single crystal. Depth profiling also indicates that the Fe-rich structure is located in the surface region, while the Si-rich structure exists in the deeper region. In conclusion, this analytical technique is a powerful tool for solid samples such as nuclear materials and fuels.

Oral presentation

Surface structure on $$beta$$-FeSi$$_2$$ substructure formed by heat-treatment in ultrahigh vacuum

Matsumura, Seidai*; Ochiai, Kunihito*; Udono, Haruhiko*; Esaka, Fumitaka; Yamaguchi, Kenji; Yamamoto, Hiroyuki; Hojo, Kiichi

no journal, , 

no abstracts in English

Oral presentation

Surface characterization of $$beta$$-FeSi$$_{2}$$ single crystal by synchrotron-radiation X-ray photoelectron spectroscopy and X-ray absorption spectroscopy

Esaka, Fumitaka; Yamamoto, Hiroyuki; Udono, Haruhiko*; Matsubayashi, Nobuyuki*; Yamaguchi, Kenji; Shamoto, Shinichi; Magara, Masaaki; Kimura, Takaumi

no journal, , 

Surface characterization of $$beta$$-FeSi$$_{2}$$ single crystal has been performed by synchrotron-radiation X-ray photoelectron spectroscopy and X-ray absorption spectroscopy.

Oral presentation

Surface depth profiling of FeSi$$_{2}$$ single crystals by synchrotron radiation excited XPS and XAS

Esaka, Fumitaka; Yamamoto, Hiroyuki; Udono, Haruhiko*; Matsubayashi, Nobuyuki*; Yamaguchi, Kenji; Shamoto, Shinichi; Magara, Masaaki; Kimura, Takaumi

no journal, , 

Surface depth profiling of FeSi$$_{2}$$ single crystals has been performed by synchrotron radiation excited XPS and XAS.

Oral presentation

Heat-treatment of $$beta$$-FeSi$$_2$$ substrate under Si vapor and homoepitaxy

Matsumura, Seidai*; Yamanaka, Yusuke*; Udono, Haruhiko*; Yamaguchi, Kenji; Esaka, Fumitaka; Hojo, Kiichi

no journal, , 

no abstracts in English

35 (Records 1-20 displayed on this page)