CO12-1

Thickness and Density of Adsorbed Additive Layer on Metal Surface
Evaluated by Neutron Reflectometry

Dept. of Mechanical Engineering, Doshisha University
Dept. of Mechanical Engineering, Doshisha University
2
Research Reactor Institute, Kyoto University
1

INTRODUCTION: Boundary lubrication is one of themost interesting topics in the field of tribology, and therecent development of physical and chemical analyzers
has created a need for better understanding of the behavior of boundary lubrication films. Under the boundary
lubrication, oiliness additives mixed in base oil are expected to form adsorption layers on a sliding surface andthen achieve low friction and high durability. Previous
reports have confirmed that the adsorptive performanceof the additive to the surface greatly affects the friction
coefficient of surface. However, physical properties ofadsorbed layers are still unknown because of the substantial difficulty for in-situ analysis.
Our laboratory has proposed applying neutron reflectometry to directly measure physical properties, i.e.,
thickness and density, of adsorption layers formed byacid additives on metal surfaces [1,2]. We report thephysical properties of adsorption layer and introduce ourlatest approach with the development of the TOF-mode
neutron reflectometer for tribology use.
EXPERIMENTS: To widen applications of the neutronreflectometry to tribological studies, a TOF-mode neutron reflectometer was developed at the CN-3 in Kyoto
University Research Reactor Institute (KURRI). A schematic diagram is shown in Figure 1. The carbonization
nickel surfaces with various film thicknesses were deposited on ultra-flat silicon blocks by physical deposition.
The obtained reflectivity profiles in air proved that theresolution of the developed reflectometer for film thickness was under 2 nm. This result proved that the reflectometry has high potential for use in advanced tribological studies on solid-liquid interfaces.
DS

Chopper S1

S2

2θ

Shutter
Beam

1000

In PAO+Stearic acid (10h～20h)
In PAO+Stearic acid (～10h)

100

10

1

0.1

0.01

Sample1260

RESULTS: The carboxylic groups in the acetic acid in
the lubricant were expected to preferentially adsorb to themetal surface and form a thin layer less than 10 nm thick.
To examine the layer thickness and density using neutronreflectometry with the highest accuracy, we took the following procedure. First, we set the sample surface in thesample holder to obtain a neutron reflectivity profile fromthe interface between the sample surface and air. Second,
the base oil poly-alpha-olefin (PAO) was poured into thesample holder and a reflectivity profile from between thesurface and the PAO was similarly obtained. Finally, theadditive was added into the PAO and mixed in the sample
holder carefully and the reflectivity profile was again
obtained. During the whole experiments, we didn’t touchthe neutron optics and the sample holder at all, and thus
the difference in reflectivity profiles in each step werecompletely recognized as being provided by the existenceof base oil and/or additive at the interface. After theabove procedure, we checked the difference between thereflectivity profiles with theoretical fitting based on Parratt’s theory. The amount of additive mixed into PAO was
0.1 mass%.
The obtained reflectivity profile is shown in Fig. 2.
From the obtained reflectivity profiles, the thicknesses of
the adsorption layer on the copper surface were quite thin,approximately 1.0-2.5 nm. To investigate the effect ofadsorption layer on the tribological properties, friction
tests were carried out for copper surfaces with aball-on-disk tribometer. The results showed that the friction coefficient decreased when any additive was mixed
into the base oil. The results are summarized as follows.
(1) Formation of the adsorption layer was clearly observed when the acetic, undecanoic, and stearic acids
were used as additives for each. Particularly, the adsorbed
layer of acetic acid was expected to be a multi-layer one.
(2) Oiliness additives with long carbon-chains required
several hours to form the stable adsorbed layers.

Reflectivity (free scale)

T. Hirayama, Y. Konishi1, M. Maeda1, T. Matsuoka1, M.
Hino2, M. Kitaguchi2 and T. Oda2

In PAO△□◇ Exp.
Cal.

150

1110

940

0.001
0.01

0.02

0.03
-1

370
2050
2890

Fig. 1. Schematic diagram of reflectometer in KURRI.

q [Å ]

Fig. 2. Reflectivity profiles from copper surface.
REFERENCES:[1] T. Hirayama et al., Trans. JSME, Ser. C, 77, 779(2011) 2884-2893.
[2] T. Hirayama et al., Tribol. Int. (2012) in press.

採択課題番号 23014 中性子反射率法による金属表面上添加剤吸着層の厚み・密度測定 共同通常
（同志社・理工）平山朋子、小西洋平、前田成志、松岡 敬（京大・原子炉）日野正裕、北口雅暁、
小田達郎

Neutron Activation Analysis on Hafnium Oxide )ilms

T. Takatsuka, K. Hirata, Y. Kobayashi and K. Takamiya1
National Metrology Institute of Japan, National Instituteof Advanced Industrial Science and Technology
1
Research Reactor Institute, Kyoto University
INTRODUCTION: Hafnium oxide (high-k) dielectricfilms are being introduced into silicon-based semiconductor devices in order to achieve higher electronic performance. The front-end processes require the thin dielectric films well-controlled in thickness for gate stacks.
According to the international technology roadmap for
semiconductors 2011[1], thickness of dielectric films
should be controlled in 4 % process range. It becomesdifficult to obtain the accurate thickness in length unit
since the films are getting to be near atomic dimension
and consist of complex structure like interface layers,which may involve atomic fluctuations. Reference materials whose properties are well-calibrated should shedlight on quantification of the film thickness with small
uncertainties. This study aims to quantify hafnium inthin hafnium oxide films by isotope dilution neutron activation analysis [2] as quantitative method, and finally todevelop reference materials applicable to semiconductor
manufacture.
EXPERIMENTS: Hafnium oxide films were deposited on 4-inch Si wafers by magnetron sputtering method.
In this study, the targeted thickness is 2.5 nm with homogeneity within 1% in a wafer. Several wafers withhafnium oxide film were diced into 15 × 15 mm2 pieces,and several pieces were randomly picked-up for measurements.
Hafnium amounts were evaluated by INAA and calculated into area density. The surface area of a specimen
was measured by taking images using a commercial optical scanner with a high resolution. From the images,
the lengths of four sides of the chip were measured to
calculate the surface area. Length calibration was performed by standard scales. For the production of standards to calibrate hafnium amounts, a natural standard
solution was prepared by diluting SRM 3122 (commercially available from NIST) gravimetrically. In addition,a spike solution for isotope dilution was prepared by dissolving a 179Hf enriched HfO2 in HNO3+HF+H2SO4 solution, followed by diluting gravimetrically. Portions of
the solutions were dropped from a polyethylene pipette
onto pieces of the cleaned specimen and blank Si chips.
All specimens and standards were heat-sealed in individual clean poly-ethylene envelopes and stacked in apoly-ethylene irradiation container. The neutron irradiation was performed for 4 hours at 1 MW in research
reactor KUR of Research Reactor Institute, Kyoto University. Gamma-ray activity of each specimen andstandard was measured by a high-purity germanium de-tector (ORTEC) with an energy resolution around 1.8
keV FWHM at 1333 keV.
RESULTS: Figure 1 shows a gamma ray spectrum
obtained from the specimen of spike solution on hafniumoxide film. Several peaks can be clearly seen and someof them are from 181Hf and 180mHf as indicated in Fig.1.
The peaks at around 133 keV and 215 keV were pickedup, the counts in each peak were integrated for every
specimen and standard, and then the intensities after the
decay correction [3] were used to determine hafnium
amount in the oxide film. The hafnium content in thespecimen is estimated to be 4.3 µg, calculated by using
the formula shown in Ref [2]. Considering the surface
area of the hafnium oxide film is 223 mm2, the resulting
hafnium content is in agreement with the content estimated from the film thickness.

105
181

Hf

181

Hf

181
180m

Hf

104
Counts (arb. unit)

CO12-2

180m

Hf

Hf
180m

Hf

103

102

101
0

100

200
300
400
Energy (keV)

500

600

Fig. 1. Gamma ray spectrum of the spike solution
on hafnium oxide film.

REFERENCES:[1] The International Technology Roadmap for Semiconductors 2011.
[2] C. Yonezawa et al., Anal. Chem., 55 (1983)
2059-2062.
[3] G.Gilmore and J. D. Hemingway, Practical gamma-ray spectrometry (John Wiley & Sons, Chichester,1995).

採択課題番号 23071 中性子放射化分析によるハフニウム酸化膜中ハフニウムの定量（産総研・計測標準）小林慶規、平田浩一、高塚登志子

一般通常CO12-3

A Brain Radiation Necrosis Model in Laboratory Animals

E. Yoritsune, M. Furuse, T. Miyata , T. Kuroiwa,
S. Masunaga1, H. Tanaka1, N. Kondoh1, A. Maruhashi1,
K. Ono1 , S-I. Miyatake
Department of Neurosurgery, Osaka Medical College
1
Research Reactor Institute, Kyoto University
INTRODUCTION: Since medical treatment apparatus
progressed in recent years, the high dose radiotherapy tothe brain tumor becomes possible, and, as a result, theprognosis of the brain tumor has improved. On the other
hand, the brain radiation necrosis which arises during thelong-term observation period after intensive radiotherapy
becomes a serious problem. Although a part of molecularmechanism in a brain radiation necrosis was shown by
our previous research, in order to prove these hypotheses
strictly, it is necessary to create a brain radiation necrosis
model in laboratory animals, and to analyze the pathology for each stage. Understanding the regulation mechanism of the cytokine in the brain radiation necrosis may
have an important role in the treatment development.
EXPERIMENTS:
Fifty 12-wk-old female Sprague-Dawley rats with body weight 229
20 grams
were divided into 5 separate batches to receive irradiationof 20, 25, 30, 35 or 40 Gy to the right hemibrain with asingle collimated (10mm10mm) 60Co gamma-ray
irradiator under anesthesia. Gamma-ray irradiation
was applied using a 60Co gamma-ray irradiator in
the KUR. The irradiation method referred to the reportof Wang et al., Li et al., and Nordal et al.[1, 2, 3]. Threerats died due to anesthesia. A total of 47 rats were irradiated with 20 Gy (n = 5), 25 Gy (n = 5), 30 Gy (n = 22),
35 Gy (n = 10) and 40 Gy (n = 5), respectively.
RESULTS: In all rats in the 40 Gy cohort, body weightdecreased and died within several days after irradiation.
Seven rats in the 35 Gy cohort and ten rats in the 30 Gy
cohort were found to have abnormal signs of gait andmovement from 24 weeks post-radiation. No gross neurologic abnormalities were observed in other rats. Standardized H&E staining was used to detect morphologic
characteristics of brain tissue between 20 and 28 weeks
after irradiation. There were no apparent histopathological abnormalities in the brain, including white matter andblood vessel changes after all dose, as shown in Fig.1.

Fig. 1.
H&E staining in the specimen of the 35 Gy irradiatedbrain 20 weeks after irradiation. There were no apparent
histopathological abnormalities. (Original magnifications,
10,
200)

REFERENCES:[1] S. Wang et al. Longitudinal diffusion tensor magnetic
resonance imaging study of radiation-induced white matter damage in a rat model. Cancer Res (2009)69:1190-1198.
[2] Y. Li et al. Hypoxia in radiation-induced blood-spinal
cord barrier breakdown. Cancer Res (2001)
61:3348-3354.
[3] RA. Nordal et al. Hypoxia and hypoxia-inducible
factor-1 target genes in central nervous system radiation
injury : A role for vascular endothelial growth factor.
Clin Cancer Res (2004) 10:3342-3353.

	
 採択課題番号 23072	
 放射線壊死の病態解明と新規治療法の研究（大阪医科大学・脳）古瀬元雅、頼經英倫那、宮田とも、宮武伸一、黒岩敏彦（京大・原子炉）小野公二、増永慎一郎、田中浩基、近藤夏子	
 
	
 

共同通常

CO12-4

Characterization for U-type and Straight-type 3He PSD

Y. Kawakita, T. Nakatani, T. Yamada1, N. Takahashi,
R. Kajimoto1, M. Nakamura, S. Ohira-Kawamura and
M. Sugiyama2
J-PARC, Japan Atomic Energy Agency
1
CROSS Tokai
2
Research Reactor Institute, Kyoto University

EXPERIMENTS: The PSD detectors, an amplifier
and a power source for PSD were supplied by Toshiba
Electron Tubes & Devices Co., Ltd. To investigate positional resolution, proportionality and detectable region of
PSD, CN-2 port was utilized during Oct. 4-6 and Nov.
15-16, 2011. Neutron beam irradiated a PSD set on thesample table through a slit of 1mm in width and 14mm inheight. 5 minute irradiation at the reactor operation of
1MW provides enough counts around 2.4×104 at the peakfor PSD with 6 atm 3He gas and 1/2 inch diameter.
3

RESULTS: Fig. 1 shows the sketch of the U-type He
PSD and the irradiated position. Fig. 2 shows the results
for the positional resolutions of (a) the U-type PSD with
6 atm 3He gas in the tube of 1/2 inch diameter and (b) thestraight PSD with 1/2 inch diameter and 6 atm 3He gaspressure. In general, the positional resolution of PSD ishigher at the middle of the tube than at the end. Even
U-type PSD exhibits such a tendency. Both the open
edges of U-shape show larger FWHM values, while theconnected bottom of U-shape shows a relatively small
FWHM. The proportionality of the detecting position isquite good for both U-type and straight-type PSD’s. A
300 mm length straight PSD with 21.4 atm gas pressurein the 1/4 inch tube has the highest resolution of 3.43 mm
due to the effects of gas pressure of 3He, small diameterof the tube.

3

FWHM (mm)4.8(a) U–type He PSD

4.6
4.4
4.2
4
–200

0
Position (mm)

200

3

5
FWHM (mm)INTRODUCTION: Development of neutron detectors
is a key to realize new instruments in Materials and Life
Science Experimental Facility in J-PARC. Although various detectors have been developed, position sensitive
detectors (PSD) with 3He gas still have superior to theothers in counting rate and so on. For DNA back scattering instrument installed at the BL02 port [1, 2], U-type
PSD which consists of two short straight PSD’s connected at the one end have been newly developed as counters
for inelastic experiments (see Fig. 1) as well as a conventional straight-type PSD for diffraction. Hardness to obtain 3He gas is a serious problem in neutron science.
Therefore, we need to optimize diameter and gas pressureof PSD. The purpose of this study is to measure positional resolutions for various 3He PSD’s with different gas
pressures and shapes and to obtain direction in detector
optimization. Moreover, newly developed U-type detectors for DNA must be examined for quality stabilization
respective in positional resolution.

Fig. 1. Sketch of U-type 3He PSD and the irradiated positions .

(b) straight–type He PSD

4.8
4.6
4.4
4.2

–200

0
Position (mm)200

Fig. 2. Positional resolution of (a) U-type 3He PSD
at the positions of ±43, ±81.5, ±117, ±150, ±188 mm
from the connection (the bottom of the U shape) and(b) straight-type 3He PSD at the positions of ±300,±150, 0 mm (center of the tube).
REFERENCES:[1] K. Shibata, N. Takahashi, K. Nakajima, H. Nakagawa,
S. Fujiwara, Y. Kawakita and T. Sato, Hamon 20 (2010)13-15.
[2] N. Takahashi, K. Shibata, T.J. Sato, I. Tamura, R.
Kajimoto, S. Harjo, K. Oikawa, M. Arai and F. Mezei, J.
Phys. Chem. Solid. 68 (2007) 2199-2203.

採択課題番号 23079 U 字型および直管型 3He 位置敏感型中性子検出器の性能評価（原子力機構・J-PARC）川北至信、中谷健、高橋伸明（総合科学研究機構）柴田薫、蒲沢和也、山田武（京大・原子炉）杉山正明

共同通常

CO12-5

Evaluation for Radioactive Inventory of Structural Materials Induced by
Neutron Activation

T. Aratani, K. Kumagai, T. Kosako and K. Takamiya1
Graduate School of Engineering, Tokyo University
1
Research Reactor Institute, Kyoto University

INTRODUCTION: In decommissioning of nuclear
power plants, radioactive inventory of structural materials
in the facility induced by neutron activation generated
from the reactor is a major problem. For example, inview of estimation for exposure of occupationally exposed persons involved in demolition work of nuclear
facilities, public safety assessments, plans for demolition
work of nuclear facilities, evaluation of radioactive
wastes, and so on. Evaluation for radioactive inventory isnecessary information to carry out decommissioning
safely and reasonably.

Evaluation for radioactive inventory, however, becomes overly conservative by being taken likelihood on
the safety assessment in the present situation. As problems in the evaluation, there are three points as follows.
 Accurate material composition should be used fordomestic nuclear facilities.
 Newest activation cross section should be used in theevaluation.
 Realistic spectrum should be used on the assumptionof neutron energy spectrum of a typical LWR.
This study focuses on material composition, and calculate radioactive inventory more reasonable. The purposeof this study is to contribute to improve the accuracy ofthe evaluation of radioactive inventory, focusing particularly on the main structural materials [1], [2], [3].

EXPERIMENTS: This experiment aims to establish
an experimental system that simulates the neutron spectrum of a typical LWR. Optimal moderator to reproduce
the neutron spectrum of a typical LWR is evaluated byUsing MCNP-5. And then, the neutron irradiation experiment is implemented through an evaluated moderator.
In order to reproduce the spectrum of typical LWR, it isnecessary to moderate the energy spectrum of neutrons of
Slant. As a moderator, 250μm thickness cadmium is
adopted for the adjustment of the spectrum. According to
Figure 1, moderated spectrum is close to the goal spectrum of LWR.
In this experiment, irradiated materials are Iron and
SUS304. Size of the Iron sample is 10mm diameter and20mm height, and weight is about 12g. And size of the
SUS304 sample is 1.0mm diameter and 20mm height,
and weight is about 0.12g. These samples should be putin polyethylene capsule.

Fig.1 Transmission spectrum
RESULTS: Table.1 shows a list of radioactivity ofeach nuclide in irradiated Iron. Radioactivity of Mn-56
is seen remarkably. But radioactivity of other nuclides is
not seen well. Table.2 shows a list of radioactivity of eachnuclide in irradiated SUS304. Radioactivity of Mn-56 isalso seen remarkably. And radioactivity of 51Cr and 58Co
are seen
Table.1 List of radioactivity (Iron)

Table.2 List of radioactivity (SUS304l)

REFERENCES:[1]M. Hashimoto, T. Iimoto, and T Kosako, applicabilityof convex hull in multiple detector response space forneutron dose measurements, Radiation Protection
Dosimetry, Vol.136, No.1, 1-10(2009.7)[2]LUO Zhiping, MA Jizeng, LIU Liye, CHEN Baowei,
Takeshi IIMOTO and Toshiso KOSAKO, Development of a Gas Scintillation Proportional Counter,Radioisotopes, Vol.57, no.11, 695-701, (2008. 11)[3]M. Ishikawa, K. Ono, Y. Sakurai, H. Unesaki, A.
Uritani, G. Bengua, T. Kobayashi, K. Tanaka and T.
Kosako, Development of real-time thermal neutron
monitor using boron-loaded plastic scintillator with
optical fiber for boron neutron capture therapy,Applied
Radiation and Isotopes, 61(5), 775-779, (Nov. 2004)

採択課題番号 23082 放射性核種生成量評価のための中性子による材料照射の研究（京大・原子炉）高宮幸一（東大院・工）新谷俊幸、 熊谷一城、 小佐古敏荘

共同通常