Yonsei University – Shizuoka University
Students Workshop 2012

Proceedings

August 24, 2012
Shizuoka University, Hamamatsu, Shizuoka

ProgramYonsei University – Shizuoka University Students Workshop 2012
August 24 (Fri), 2012 at Shizuoka University, Japan
Program
10:00-10:30

Registration

10:30-10:40

Opening Remark

10:40-11:10

O-01 (Invited)
Development of Interactive Nanomanipulators Based on Scanning
Probe Microscopes
Professor Futoshi Iwata

11:10-11:25

O-02
High Spatial Resolution Luminescence Microscopy with Direct
Electron Beam Excitation for Dynamic Live Cell Imaging       11
Yasunori Nawa, W. Inami, A. Chiba, A. Ono, A. Miyakawa,Y. Kawata, S. Lin, and S. Terakawa (Shizuoka University)

11:25-11:40

O-03
Refractive Media Flatness Measurement by Phase Shifting Digital
Holography    13

Sungbin Jeon, Janghyun Cho, Do-Hyung Kim, No-Cheol Park
(Yonsei University)
11:40-11:55

O-04
Deep-UV Surface Plasmon Resonance for the Enhancement of
Fluorescence Excitation    15

Masakazu Kikawada, A. Ono, W. Inami, and Y. Kawata(Shizuoka University)
11:55-12:10

O-05
Air Gap Control System for High Speed Plasmonic Lithography
with Solid Immersion Lens Optical Head    17

Guk-Jong Choi, Won-Sup Lee, Taeseob Kim, Geon Lim, No-Cheol Park
(Yonsei University)

12:10-13:45

Lunch13:45-14:00

O-06
Micro-Processing of HeLa Cells with Electron Beam    19

Ken Watanabe, W. Inami, Y. Kawata (Shizuoka University)
14:00-14:15

O-07
Development of a MEMS-based Wear Tester
Shin-Sung Yoo, Dae-Eun Kim

14:15-14:30

    21

(Yonsei University)

O-08
The Numerical Analysis of Intensity Distribution of Light    23

Excited by Electron Beam in a Luminescent Film
Masahiro Fukuta, W. Inami, A. Ono, and Y. Kawata (Shizuoka University)
14:30-14:45

O-09
3D Thickness Profile Measurement of a Metal Film Using    25

a Film Removal Process
Hang-Eun Joe, Dae Su Kim, Sang Jo Lee, Byung-Kwon Min(Yonsei University)

14:45-15:00

Coffee Break

15:00-15:15

O-10
Development of Optically Controllable Electrophoresis    27with a Photoconductive Substrate
Taiki Nagashima, W. Inami, and Y. Kawata (Shizuoka University)
15:15-15:30

O-11
Image Reconstruction for Potable Digital Holographic      29

Microscopy Using Glass Phase Shifter
JaeHyeong Park, Janghyun Cho, Sungbin Jeon, Sang Jo Lee, Kyung Soo Lee(Yonsei University)
15:30-15:45

O-12
Measurement of Electron Transmittance of Fluorescent    31

Thin Film with a High Electron Stopping Power Layer
Takuya Miyazawa, Y. Nishimura, W. Inami, Y. Kawata (Shizuoka University)

15:45-16:00

Closing Remark

Proceedings

O-02

High spatial resolution luminescence microscopy
with direct electron beam excitation for dynamic live cell imaging
Yasunori Nawa1, Wataru Inami2, 3, Atsushi Ono2, 3, Aki Miyake3, 4, Sheng Lin5,
Yoshimasa Kawata1, 3, 4*, and Susumu Terakawa3, 5
1
Graduate School of Science and Technology, Shizuoka University
2
Division of Global Research Leaders, Shizuoka University,
3
CREST, Japan Science and Technology Agency, Japan
4
Department of Mechanical Engineering, Shizuoka University
5
Medical Photonics Research Center, Hamamatsu University School of Medicine*
3-5-1Johoku, Naka, Hmamatsu, Shizuoka 432-8561, Japan
TEL: +81-53-478-1069
e-mail: kawata@eng.shizuoka.ac.jp

Abstract
We have developed a direct electron beam excitation assisted optical microscope with aresolution of a few tens of nanometers. The microscope is a combination of a fluorescencemicroscope and a scanning electron microscope, and it enables dynamic observation of
specimens in liquids with high spatial resolution. This technique is also used for live cell
imaging under physiological condition.

1. Introduction

2. Principle of the D-EXA microscope

Nano-imaging of specimens in liquids ishighly required in the wide range of physical,
chemical, and biological applications.
Especially imaging biological specimens incells is crucial for a deeper understanding ofcell functions. Fluorescence microscopy has
been widely used to analyze the dynamic
behavior of cellular elements in living cells,
because stained molecules of interest in thespecimens can be imaged with high contrast.
However, the spatial resolution of thestandard fluorescence microscope is limitedby the diffraction limit of the light.
Recently several approaches to analyze
nanostructures in cells under physiologicalcondition are introduced. These techniques
allow to extend the spatial analysis beyond
the limit of the optical microscopy.
Here, we propose a direct electron beam
excitation assisted optical microscope(D-EXA microscope) for high spatial
resolution live cell imaging. The microscopeis one of the super-resolution fluorescencemicroscopes combining a scanning electron
microscope (SEM) with a fluorescencemicroscope. We observed ZnO nanoparticles
as a fluorescent material, and demonstrated
the application to live cell imaging in culture
solution using a prototype D-EXA
microscope.

Figure 1 shows the principle of the
D-EXA microscope.

11

Fig. 1. The principle of the D-EXA microscope.
A focused electron beam directly excites
cathodolumiescence in the specimens throughthe thin film. A spatial resolution of a few tensof nanometer is achieved.

Specimens are directly placed on a thinfilm and stained with fluorescent materials.
Fluorescent materials in the specimens are
directly excited with a focused electron
beam through the thin film.
High spatial resolution is realized,
because the focused electron beam can befocused to an area of a few tens ofnanometers in specimens.
Since the thin film separates the vacuum

from the environment such as air or liquid,
the specimens do not need to be in vacuum
and it is possible to observe the dynamic
behavior of live cells under various
conditions. Cathodoluminescence images arereconstructed with raster scanning of theelectron beam.

3. The spatial resolution of the
D-EXA microscope
Figures 2A and 2B show luminescence
images acquired with the D-EXA
microscope
andaconventional
epi-fluorescencemicroscope
underatmospheric pressure, respectively. The
particle size is 100 nm. The ZnO
nanoparticles in figure 2A are resolved moreclearly compared to figure 2B.
Figures 2C and 2D show line profiles of
the region between the arrows in figures 2A
and 2B. The D-EXA microscope is able todistinguish each ZnO nanoparticle. The
spatial resolution of the D-EXA microscopeis greater than 100 nm.

auto-fluorescence in biological cells. First,
we thus observed auto-fluorescence of thecells without any treatments such as fixing
and staining processes.
Figures 3A and 3B show the
auto-fluorescence image acquired with the
D-EXA microscope and a phase contrast
microscope
imageoflivingMARCO-expressing CHO cells in culture
solution. In figure 3A, the shape of each cell
was clearly recognized and some brightspots were observed in cells. We believe thatthe bright spots indicated with arrows wereauto-fluorescence of intracellular granules
andlight-grey
regionswereauto-fluorescence of cell membranes. It isclearly demonstrated that the D-EXA
microscope is useful tool for observation ofliving biological cells in physiologicalconditions.

Fig. 3. Observation results of living
MARCO-expressing CHO cells in culture
solution. (A) An auto-fluorescence image
acquired with the D-EXA microscope. (B) A
phase contrast microscope image of the cells.

5. Conclusion

Fig. 2. Luminescence images of 100 nm ZnO
nanoparticles. (A) A cathodoluminescence
image acquired with the D-EXA microscope.
(B) A fluorescence image excited with UV
wavelength in epi-fluorescence microscope. (C,D) The luminescence distribution between thearrows in figures 2A and 2B respectively.

We have developed the D-EXA
microscope as one of the super-resolution
fluorescence microscope with direct electron
beam excitation. A spatial resolution greaterthan 100 nm was achieved. Living cells weresuccessfully observed in water based
solution with high spatial resolution. The
D-EXA microscope can be applied for the
analysis of cell functions staining withfluorescent materials such as ZnO.
Reference

4. Dynamic live cell imaging
Anelectronbeam

excites

12[1] Y. Nawa, W. Inami, A. Chiba, A. Ono, A.
Miyakawa, Y. Kawata, S. Lin, and S.
Terakawa, Opt. Exp. 20, 5629 (2012).

O-03

Refractive media flatness measurement by phase-shifting digital holography
Sungbin Jeon, Janghyun Cho, Do-Hyung Kim, No-Cheol Park*
Department of Mechanical Engineering Center for Information Storage Device
50 Yonsei-ro, Seodaemun-gu, Seoul Korea 120-749
TEL&FAX: +82-2-365-8460*
e-mail: pnch@yonsei.ac.kr

Abstract
Digital holography can be used in various application including the measurement of
flatness of surface. In this paper, the transmittive phase-shifting digital holography is used toacquire the surface profile of refractive media with high-resolution.

1. Introduction
One of the applications of digitalholography is measuring the surface profile.
Thisinterferometricapproachhasadvantages for nano-scale precision,
noncontacting and whole-field measurement.
In recent years, many methods like Fizeau[1]] and Twyman-Green [2] interferometers
were developed. But most of these researchwere to use the information in reflected
object beam. Reflective interferometer canmeasure any types of media, but it also has
the weakness of error of object stage, likeangular tilt or roughness of stage. In addition,reflective method can only measure theflatness of surface in one side. To overcome
these problem, we propose the transmissivephse-shifting digital holography.

2. Phase-shifting Digital Holography

Phase-shifting digital holography is themethod which can eliminate the zero andminus-first order diffracted wave. It requires
at least two holograms with phase-different
reference wave. From these holograms, thecomplex amplitude can be easily acquired by
calculation [3] The phase distribution
obtained from it can be converted into thesurface profile or flatness of both side ofplate. In addition, phase-shifting digitalholography can apply in-line setup, andusable CCD area is much bigger than otheroff-axis holography method. Thus it canmeasure large surface at once.

3. Phase-shifting Holographic
Flatness Measurement
Figure 1 illustrates the schematic of asystemconfigurationofflatnessmeasurement for refractive media using
phase-shifting digital holography. The light

Fig. 1 System configuration of flatness measurement for refractive media using phase-shifting digitalholography

13

Fig. 2 (a) Acquired complex amplitude from phase-shifting holography (b) Calculated surface profile of
the area denoted in Fig. 2 (a)source is Nd: Yag laser with a wavelength
λ = 532 nm. The CCD has an array of
2448 × 2050 pixels, wich is cropped into
2050 × 2050 due to simplicity incalculation. The size of each pixel is
3.45 µ m. The transparent plate is locatedin object plane to acquire the phase-shiftedinterference image. To shift the phase of
the reference wave precisely, phase SLM isused. The microscopy lens was used toincreasethelateralresolutionofmeasurement.
Figure 2 shows the experiment result
using the proposed setup. The BK7 glass
plate printed with USAF chart was used. In
this paper, 2-step phase-shifting holography
with phase difference of π / 2 . The
complex amplitude acquired from holograms
is shown in Fig. 2(a). Figure 2(b) is thesurface profile of the glass plate of partial
area. Since the glass is not well-polished, thethickness difference of surface is up to
350nm.

4. Conclusion
In this research, the flatness of refractive
media plate is measured using transmissive
phase-shifting digital holography. Using thissetup the surface profile can be obtained fast,and less error compared with conventional
interferometric method.

14

Reference[1] D. Bhattacharyya, A. Ray, B. K. Dutta,
and P. N. Ghosh, "Direct measurementon transparent plates by using Fizeau
interferometry," Optics &amp; Laser
Technology 34, 93-96 (2002).
[2] O. Kwon, J. C. Wyant, and C. R.
Hayslett, "Rough surface interferometryat 10.6 µm," Appl. Opt. 19, 1862-1869(1980)[3] I.
Yamaguchi
andT.
Zhang,"Phase-shifting digital holography,"
Optics letters 22, 1268-1270 (1997)

O-04

Deep-UV Surface Plasmon Resonance for the Enhancement of Fluorescence
Excitation
Masakazu Kikawada1, Atsushi Ono2,3, Wataru Inami2,3, and Yoshimasa Kawata1,3*
1Faculty of Engineering, Shizuoka Univ.

2Division of Global Research Leaders, Shizuoka Univ.

3CREST, Japan Science and Technology Agency, Japan

3-5-1, Johoku, Naka, Hamamatsu 432-8561, Japan
TEL&FAX: +81-53-478-1076*e-mail: Kawata@eng.shizuoka.ac.jp

Abstract
We present the enhancement of fluorescence excitation with deep ultra-violet surface plasmon
resonance (DUV-SPR). It is found that aluminum is good material to excite SPR with DUVlight. We also demonstrate fluorescence enhancement of quantum dots with field enhancement
effect of DUV-SPR.

1.

Introduction

Recently, surface plasmon resonance(SPR) has attracted much attentions invarious fields such as optical bio-sensors,
high efficient LED, solar panels, etc.,
because it enables to enhance the electricfield of incident light by several tens times.
Many applications of SPR using visible lightor near infrared light have been reported [1].
The techniques of SPR in red or infrared
region have been well established.
SPR in DUV region are also reported
some groups [2]. These researches achieved
nanoscale resolution beyond the diffraction
limit of light. We also reported theenhancement of photoelectron emission [3].
The photoelectric current was enhanced 9times due to field enhancement by DUVSPR.

2.

The metals such as gold and silver, which
are good materials to excite SPR in
visible region, can’t be used in DUV,
because they have large absorption in the
wavelength region.
3.

Experimental set-up for DUV-SPR
excitation and fluorescenceenhancement

We evaporated aluminum of 26 nm
thickness on a prism surface at the conditionof Kretchmann configuration shown in figure
2. A fluorescent material is coated on thealuminum thin film.
DUV laser is irradiated boundary
between prism and the aluminum thin film.
We measured the intensity of reflected lightand fluorescence with changing incident
angle.

Metal for DUV-SPR Excitation

The permittivity of metal is very
important to excite DUV-SPR. It isnecessary that its real part should be
negative and its imaginary part to should
be small imaginary part. We use
aluminum to excite DUV-SPR. Figure 1(a) and (b) show permittivity dispersionof real part and imaginary partrespectively. Aluminum is a goodmaterial to excite SPR in DUV region.

15

Fig. 1. (a) Permittivity of real part and (b)Permittivity of imaginary part. Red line isaluminum. Blue line is gold. Green line is silver.

4.

Results of reflectance andfluorescence intensity

Figure 3(a) shows experimental result ofreflectance dependence on the incident angle.
Red line and blue line indicate p-polarizationand s-polarization, respectively. Reflectancedrastically decreases around 49 degrees at ppolarization. On the other hand, reflectance isalmost constant at s-polarization. In thisresult, we successfully excited SPR in DUVregion.
Figure 3(b) shows calculation result ofreflectance. Blue line indicates reflectance at
the aluminum thickness of 26 nm.
Reflectance drastically decreases around 44
degrees. The angle which reflectancedecreases of experimental result and the oneof calculation result don’t correspond in thisresult. Moreover, reflectance of experimental
result and calculation result don’t correspond.
We calculated reflectance consideringwith the condition that the aluminum surface
was oxidized, because, aluminum is easily tooxidized at the atmosphere. Red line of figure3(b) indicates reflectance of 19 nm aluminum
thickness and 5 nm oxidized of aluminum.
Experimental result shows good agreementwith calculation result.
We demonstrated DUV-SPR excitation
for fluorescent enhancement. We used
quantum dots as a fluorescent material. This
material absorbs the light, the wavelength ofwhich is shorter than 370 nm and emission
wavelength is 380 nm. quantum dots was
spin-coated on aluminum thin film.
Figure 4(a) shows fluorescence intensity
dependence on the incident angle.
Fluorescence intensity maximized at the 49
degrees with p-polarization excitation. On theother hands, fluorescence was constant withs-polarization excitation.
In these results, fluorescence intensity isenhanced by the excitation of DUV-SPR. The
maximum intensity of fluorescence in ppolarization is enhanced to 24 times
compared with that in s-polarization. We
measured the fluorescent spectrum shown infigure 4(b). The emission spectrum has thepeak at 380 nm wavelength with ppolarization. This peak wavelength iscorresponding to the emission wavelength ofquantum dots. We may concluded that we
succeeded fluorescence enhancement of

16

Fig. 2. Kretchmann configuration

Fig. 3. Reflectance (a) experimental result and(b) calculation result

Fig. 4. (a) Fluorescence intensity (b) Spectrum

quantum dots using DUV-SPR.

5.

Conclusion

We successfully excited DUV-SPR andachieved 24 times enhancement offluorescence intensity of Q-dot by DUVSPR. The wavelength range of SPR
excitation can be extended to the DUV region
by using aluminum. DUV has advantage ofautofluorescence observation because mostcells and organisms emit autofluorescence by
DUV illumination.
Reference[1] K. Tawa, et. al. OPTICS EXPRESS, 16,
9781 (2008).
[2] A. Taguchi, et. al. Journal of RAMAN
SPECTROSCOPY, 40, 1324 (2009).
[3] Y. Watanabe, et. al. JOURNAL OFAPPLIED PHYSICS, 109, 023112 (2011).

O-05

Air gap control system for high speed plasmonic lithography
with solid immersion lens optical head
Guk-Jong Choi, Taeseob Kim, Won-Sub Lee, Geon Lim and No-Cheol Park*
Department of Mechanical Engineering Center for Information Storage Device
50 Yonsei-ro, Seodaemun-gu, Seoul Korea 120-749
TEL&FAX: +82-2-365-8460*
e-mail: pnch@yonsei.ac.kr

Abstract
This paper introduces air gap control system of optical head with solid immersion lens(SIL) for high speed plasmonic lithography. In order to achieve nano pattern size, air gap
should be remained under 20 nm precisely. In this system, evanescent coupling effect is used
for air gap in near field (NF) and the result is about 70 nm pattern size at 100 mm/s.

1. Introduction
Plasmonic lithography is the next
generation lithography technology which
overcomes a limitation of wavelength andreduces the cost of manufacture. Thislithography method uses the nano metallic
wave guide causing the surface plasmon
resonance (SPR) effect. It can make very
narrow lithography patterning in units oftens of nanometer only when distance
between the wave guide and photoresist (PR)is within a quarter wavelength of laser
source [1]. There have been several attempts
to maintain the distance such as an air
bearing system in hard disk drive, a contact
system with probe and an active air gap
control system in near field recording [2-4].
Among these types of system, the active
control type has advantages which are lesslimitation for pattering than the air bearing
one and faster patterning speed than theprobe one. In this paper, we introduce air
gap control for plasmonic lithography anddemonstrate the performance of lithography
patterning at a speed of 100 mm/s.

nm to record pattern. The 633 nm laser isused for detecting the air gap signal.
Figure 2 (a) shows the algorithm of the
air gap control system. It has the two key
functions. One is an air gap curve. The otheris mode switching. The air gap curve isrelated with the evanescent coupling effectwhich is depending on degree of thetransmission of 633 nm laser in totalreflection condition at the bottom of the
optical head. The role of the air gap curve isthat the optical intensity changes to the air
gap. The mode switching is the algorithm
which has three modes. First mode isapproach mode which is possible for opticalhead to be closer from far field to NF.
Second mode is hand over mode that makes
approach of optical head to NF smoothly.
These two modes are essential because
feedback control is only feasible in NF.
Third mode is the air gap control whichworks by closed loop to maintain the certain

2. Air gap control system
We control the air gap between an
optical head and a PR. Figure 1 shows the
optical head composed of a voice coil motor(VCM) actuator and SIL with the nanometallic wave guide and we use
two-wavelength optics with laser sources of
408 nm and 633 nm. It is designed for 408

17

Fig. 1 Optical head with VCM actuator and
SIL. Total optical head configuration is left
figure and SIL with the nano wave guide is rightfigure. UV laser source is 408 nm and IR laser
source is 633 nm wavelength.

Mode switching

Approach

Plant (P)1

Hand-overAir gap control

Current
amplifierController

Optical Head

Wafer

te
in
d0.6
e
lz
i
a
m
o
N0.4

0.2

Optical signal

Air gap curve

ty
i 0.8
s
n

Air Gap Hand overControl

Approach

Mode Switching Servo00
Normalized Voltage (Volt)

Air gap signal

Near-field
optics

20

40

60

80
100 120
Air gap (nm)

140

160

180

200

Open loop control process
Closed loop control process

Gap (nm)(a)(b)
Fig. 2 Air gap control algorithm. (a) Block diagram of the algorithm and (b) the configuration of therelationship between the mode switching and the gap curve.

air gap. Figure 2 (b) shows the state of theeach mode with the air gap curve.

3. Results and Discussion
Figure 3 (a) and (b) show a controlled air
gap signal at 20 nm and the performance oflithography patterning, respectively. The line
width of the patterning is nearly consistent
with the calculated the beam spot of the
wave guide which is operated by finite timedifference method [4]. The conditions of theexperiment are 20 nm air gap and 100 mm/s
speed of pattern.

4. Conclusion

Reference[1] J.I Lee, M. Van der Aa, C. Verschuren, F.
Zijp and M. Van der mark, JJAP. 44(2005) 3423
[2] W. Srituravanich, L. Pan, Y. Wang, C.
Sun, D. B. Bogy and X. Zhang, Nature
nanotechnology, 3 (2008) 733[3] Y. Kim, S. Kim, H. Jung, E. Lee and J.
W. Hahn, Optics Express, 17 (2009)
19476[4] K.S. Park, T. Kim, W.S. Lee, H.E. Joe,
B.K. Min, Y.P. Park, H. Yang, S.M.
Kang and N.C. Park, JJAP 51 (2012)(accepted)

In this study, we demonstrate the
air gap control system for high speed
plasmonic lithography. We control the
air gap maintaining 20 nm, andtherefore achieve a resolution of ~70
nm with patterning speed of 100 mm/s.
Gap Servo using Mode Switch

Gap Servo using Mode Switch (Zoom In)

220

100

200

90

180

80

160

70

GES [nm]GES [µ m]

140
120
100
80

50
40
30

60

20

40

10

20
0

60

0

0.2

0.4

0.6

0.8

1
1.2
Time [sec]

1.4

1.6

1.8

2

0
0.6

0.62

0.64

0.66

0.68
0.7
0.72
Time [sec]

0.74

0.76

0.78

0.8

(a)
(b)
Fig. 3 Result of the experiment of the plasmonic lithography system. (a) Air gap control at 20 nm and(b) lithography patterning with linewidth 70 nm at 100 mm/s and the same air gap.

18

O-06

Micro-processing of HeLa cells with an electron beam
Ken Watanabe1, Wataru Inami2,3, and Yoshimasa Kawata1,3
12Faculty of Mechanical Engineering, Shizuoka University,
Division of Global Research Leaders, Shizuoka University, 3JST-CREST
TEL&FAX: +81-53-478-1076*
e-mail: kawata@eng.shizuoka.ac.jp

Abstract
Recently, development of micro fabrication for cells and other living tissues are required forbiological science. We present characteristic evaluation of cell processing using an electron
beam, in order to realize fine fabrication in nanometric region. We succeeded in processing
HeLa cells. And in this experiment, we investigated dependence of processing depth andwidth on accelerating voltage.

1. Introduction
The technologies of cell-processing arestudied widely for medicine and biology
application. In previous studies, cells are cut
by laser-ablation [1]. Figure 1 shows comparison of the resolution of laser and electron
beam. Laser processing has the resolution of
hundreds of nm-order because the resolution
is restricted by the diffraction limit of light.
On the ather hand, electron beam has theresolution of tens of nm-order.
We present cell processing using anelectron beam. The electron beam can beused for fabricate cells with a nanometricresolution since the electron beam can befocused to a few tens of nanometer. If we
can achive processing of tens nano-order, we
can get a precision to process ion channel ina cell membrane. This undeveloped
technology may accomplish an analysis of
medicine for cancer.
In our experiments, we irradiated anelectron beam to fixed and dried cells, andinvestigated dependence of the processing
depth and width on accelerating voltage ofan electron beam.

Fig. 1.

Resolution of Laser and Electron beam19

2. The experimental device forelectron beam processing
For irradiating cells with an electron beam,
we used scanning electron microscope(SEM). We used HeLa cells which wascultured on a slide glass, and carried out
fixation/dry processing in order to process ina vacuum. Figure 2(a) shows the schematic
diagram of the cellprocessing experiment.
The focused electron beam was scanned in acircle. Figure 2(b) is SEM image of aprocessed HeLa cell. It was found that the
HeLa cell was successfully processed by the
focused electron beam.
We changed accelerating voltage ofelectron beam from 2 kV to 20kV. And thevolume of electron forming electron beam
were same in all irradiation conditions.
When the spot sizes of electron beam were
35 nm and 110 nm, electron numbers were
4.38×108 and 4.44×107 electrons per 1 nm2.

Fig. 2

Electron beam processing for a cell

3. Results and Discussion
After irradiating an electron beam to a cell,
we observed the cell with an optical phasemicroscope and an atomic force microscope(AFM). Figure 3 shows an observation resultof a cell before and after irradiation ofelectron beam of 20 kV accelerating voltage.
The cell was processed with the electron
beam. In figure, the processed mark was
clearly observed. Figure 4 shows a crosssectional view of the processed cell. The cellbecome depressed at irradiated area and theprocessing depth is 135 nm.

nm is deeper than that with spot size of 110
nm because the energy of the electron beamwith spot size of 35 nm is focus to smaller
region. The depth became lager as theaccelerating voltage increased, peaking
around 10 kV.

Fig. 5. The depth dependency of irradiation area

Fig. 3. The phase- contrast microscope imagesof a cell before and after irradiation of electron
beam of 20 kV accelerating voltage

Fig. 6. The width dependency of irradiation area
Fig. 4. The results of observation in an atomic
force microscopy

The surface deformation of the cell withthe electron beam with spot size of 35 nm
was observed in the accelerating voltage
range from 2 kV to 15 kV. The depth
increased with increasing the accelerating
voltage. For the electron beam with spot sizeof 110 nm, the surface of the cell did notdeformed with the accelerating voltage ofless than 10 kV, and the processing depth
increased with the accelerating voltage ofmore than 10 kV.
Figure 6 shows the processing width
dependence on accelerating voltage of anelectron beam. The width of the grooveprocessed with the electron beam withincreased as the accelerating voltage
increased. The depth of the groove processedwith an electron beam with spot size of 35

20

4. Conclusion
We processed HeLa cells with a focusedelectron beam. The processing depth
increased with higher accelerating voltage
and smaller spot. And the processing width
increased with higher accelerating voltage
and larger spot. A focused electron beam
realizes nano processing of cells. We
optimize the spot size of electron beam andaccelerating voltage to realize finer
processing.
Reference[1]M. W. Berns, J. Aist, J. Edwards, K.
Strahs, J. Girton, P. McNeill, J. B. Rattner, M.
Kitzes, M. Kitzes, M. Hamme-Wilson,
Science, vol.213, pp.505, 1981.

O-07

Development of a MEMS-based Wear Tester
Shin-Sung Yoo and Dae-Eun Kim*

School of Mechanical Engineering, Yonsei University,
50 Yonsei-ro, Seodaemun-gu, Seoul, 120-749, South Korea
TEL: +82-2-2123-2822, FAX: +82-2-365-0491*
e-mail: kimde@yonsei.ac.kr

Abstract
Micro-Electro-Mechanical Systems (MEMS) are comprised of silicon-based micro-scale
components. In many MEMS applications, it is desirable to have moving parts such as gears,
shafts, and bearings. However, due to tribological issues of mechanical components at the
micro-scale, the reliability problems must be overcome in order to develop MEMS withmoving parts. In this presentation, the design approach for developing a MEMS-based
micro-wear tester will be discussed. Particularly, the dynamics of the actuator supporting
structure was analyzed using Finite Element Method (FEM). Such a tester is needed toinvestigate the tribological phenomena at the micro-scale.

1. Introduction
It is well known that when the size of amechanical component decreases, the effectsof surface forces become more important
than at larger scales. This is because the ratioof surface area to volume becomes large as
the dimensions decrease [1]. Due to thesereasons commercialized MEMS devices
mostly operate without large sliding motions[2]. Basically, the MEMS components
deform or move only slightly so that sliding
can be avoided [3]. However, this limits theapplication of MEMS technology in various
fields [4]. In order to overcome this problem,a clear understanding of the friction andwear characteristics at the micro-scale mustbe established. The motivation of this work
was to develop a tester that can be used toinvestigate
thewear
behaviorofsilicon-based micro-components.
Developing a wear tester at the
micro-scale is not straightforward. Basic
MEMS fabrication processes much beutilized to make the wear tester since the sizeof the components is quite small. In thiswork, a new micro-wear tester was designed
to improve the demerits of previously
developed MEMS tribotester [5].

against each other under an applied normalload for a given period of time until thesurface gets damaged by wear. Thus, it isnecessary to design a structure that can
support the applied load as well as an
actuator that can create the sliding motion. In
a MEMS-based micro-wear tester thesefeatures must be integrated in a small
volume.
Fig. 1 shows the schematic of the newly
developed micro-wear tester. The normalload is applied by the top cover which ispressed against the bottom structure. The
two components come into contact as theload is applied. The bottom component isdesigned to deflect when the normal load isapplied. Then, the bottom specimen moves
in a reciprocating motion by the MEMS
actuators that are linked to the bottom
component. This motion causes friction to
occur at the sliding interface and when thiscontinues for an extended time, thecomponents experience wear.

2. General Design
In a wear test, two components slide21

Fig.1 Schematic of the micro-wear tester

3. Structural Analysis
An important consideration in thedevelopment of the micro-wear tester shownin Fig. 1 is the integrity of the structure.
Since the parts are very small and thelinkages are thin, care must be taken toassure that these parts do not break during
the wear test. Also, since the components are
moving in a reciprocating motion, thedynamics of the system should be controlled
so that desirable sliding distance can beattained. For this purpose, FEM analyses
were performed to optimize the structuraldesign.
The main design parameters were lengthand thickness of the linkages. It was foundthat by properly designing the dimensions ofthestructure,adequatehorizontal
displacement
couldbeachieved.
Furthermore, stress analysis of thecomponents revealed that the structure wascapable of withstanding the forces generated
during the wear test.

4. Conclusion
In this research, a micro-wear tester was
designed to investigate the tribologicalcharacteristics of micro-components. The
design of the tester was optimized to produce
stable actuation in the desired range of
frequency. Also, the dimensions of thestructural parts were selected to attainadequate durability of the tester. It is
expected that the results of this work will be
used to better understand the tribologicalphenomena at the micro-scale.

5. Acknowledgement
This work was supported by the National
Foundation of Korea (NRF) grant by the
Korea
government(MEST).
(No.
2012-0001232)
References[1] J. G. Guo and Y. P. Zhao, Influence ofvan der Waals and Casimir Forces on

22

Electrostatic Torsional Actuators, J.
Microelectromech. S., 13(2004)
1027-1035.
[2] http://www.iSuppli.com, MEMS Market
Tracker, 2011.
[3] J. A. Williams and H. R. Lee,

Tribology and MEMS, J. Phys. D :Appl. Phys., 39 (2006) 201-214.
[4] W. Merlijin van Spengen, MEMS
reliability from a failure mechanisms
perspective, MIcroelectron. Reliab.,
43 (2003) 1049-1060.
[5] Z. Guo, Y. Meng, H. Wu, C. Su and S.
Wen, Measurement of static anddynamic friction coefficients ofsidewall of bulk-microfabricated
MEMS devices with an on-chip
micro-tribotester, Sensor Actuator A,
135 (2007) 863-869.

O-08

The numerical analysis of intensity distribution of light excited by electron beam ina luminescent film
Masahiro Fukuta1, 2, Wataru Inami2, 3, Atsushi Ono2, 3, Yoshimasa Kawata1, 3
1

2

Faculty of Engineering Shizuoka University, Japan
Division of Global Research Leaders, Shizuoka University, Japan
3
CREST Japan Science and Technology Agency, Japan
E-mail: kawata@eng.shizuoka.ac.jp
Abstract

We analyze the spread of cathodoluminescence occurred in the luminescent film. We
used the new analysis method that is combined the Monte Carlo simulation and FDTD
method. The Monte Carlo simulation analyzes the electron beam scattering and the
FDTD method analyzes the light scattering. In addition, we use the energy loss ofelectrons. As a result, the spot size of cathodoluminescence becomes lower withincreasing acceleration voltage.
1. Introduction

angle by colliding with atoms in theluminescent film. The distance between
scattering points and the angle calculate
by random numbers. The
cathodoluminescence is occurred by theenergy loses of electrons at scattering
process. The creation energy of one
electron hole pairs is three times of bandgap [2]. Thus, we evaluate the photons
excited by electron energy loss by divide
energy loss by three times of band gap.
We consider the cathodoluminescence asa gathering of point light sources, and we
use the dipole emission as the point lightsource. FDTD method analyzes lightscattering of dipoles. We analyze thelight scattering for each dipole and we get
the light scattering ofcathodoluminescence from sum the resultof light scattering of each dipole.

The purpose of this research is analyze
the spread of cathodoluminescenceoccurred in the luminescent film byelectron beam excitation. To achieve this,we analyze the electron beam scattering
through the luminescent film and thelight scattering of cathodoluminescence.
The electron beam scattering is analyzed
by Monte Carlo simulation and the
FDTD simulation is analyzed by FDTD
method (Finite Difference Time Domain
method). We add the energy loss
distribution of electrons in order toaccurately simulate. This study suggests
the new analysis method that combines
the Monte Carlo simulation, FDTD
method and energy loss distribution ofelectrons.
2. The analysis method of electron
beam scattering and light scattering

3. The placement of light source
In this study, we set the dipoles to themultiple points between the scattering
points. We apply the energy loss
distribution of electrons to set the dipole

We analyze the electron beam scatteringby the Monte Carlo simulation [1]. The
incident electron goes straight and change23to the multiple points. The energy loss
distribution of electrons is shown infigure 1. Figure 2 shows the relationshipbetween photon number and Z-axis
position. The photon distribution canapproximate the theoretical distribution
by set dipoles to multiple points between
the scattering points.
4. Analysis result of
cathodoluinescenceFig. 3. The relationship between FWHM
and acceleration voltage

Figure 3 is the relationship between the
FWHM and acceleration voltage. The
black point shows the result which set thedipoles to multiple points between
scattering positions and the white points
shows the result which set the dipole tothe middle points between scattering
positions. In figure 3, the FWHM become
lower with increasing acceleration
voltage. There is great variability among
the data of conventional method. On theother hand, the data of new method
improve this problem. Therefore, theresults that set the dipole to multiple
points are more accurate than the resultsthat set the dipole to middle point.
5. Conclusion
We analyzed the cathodoluminescence by
new analysis method that is combined theMonte Carlo simulation and FDTD
method. In this study, we use the energy
loss distribution of electrons and we set
dipole to the multiple points between the
scattering positions. From analysis result,the spot size of cathodoluminescence
becomeslower
withincreasing
acceleration voltage.

Fig. 1. The schematic of energy loss
distribution of electron[1] D. C. Joy, “Monte Carlo modeling forelectron microscopy and microanalysis”,
OXFORD (1995)[2] B. G. Yacobi and D. B. Holt
“Cathodoluminescence microscopy of
inorganic solids” Springer (1990)

Fig. 2. The relationship between photon
number and z-axis position

24

O-09

3D thickness profile measurement of a thin film
Hang-Eun Joe, Dae Su Kim, and Byung-Kwon Min*

School of Mechanical Engineering, Yonsei University,
50 Yonsei-ro, Seodaemun-gu, Seoul, 120-749, South Korea
TEL: +82-2-2123-6611, FAX: +82-2-365-5595*
e-mail: bkmin@yonsei.ac.kr

Abstract
Thickness of a thin film is an essential design parameter of the metal-film-based devices.
Thin film thickness has to be measured accurately that must be controlled to guarantee
performance. Although a variety of film thickness measurement methods, such as ellipsometry
and transmission electron microscopy, are employed, it is difficult to acquire the 3D thickness
profile of a thin film. In this paper, a new method to measure the 3D thickness profile of a thinfilm is proposed. To effectively measure the difference between two surface profiles, a dataalignment method using fiducial marks is proposed. The method is verified experimentallyusing Cr films.

1. Introduction
Thin-film-based devices are widely used
in industrial applications, such as sensors,
actuators, transistors, and solar cells. In manycases, the thickness of a thin film is an
essential design parameter of the devices thatmust be controlled to guarantee performance.
[1-2]. As electrical devices become more
complicated and miniaturized, 3D thickness
profile measurement with nanometer
accuracy becomes more important.
Optical interferometry can be used toacquire the 3D thickness profile of a film [3].
However, it is difficult to obtain a surface
profile of a substrate covered with opaquefilms using optical interferometry, especiallyfor metal films. The optical methods areaffected by optical properties [4]. Therefore,a 3D thickness profile measurement methodthat can be used regardless of the opticalproperties of the metal film is required.
In this paper, a new method is
proposed to measure the 3D thickness
profiles of metal films with nanometer
accuracy. The method presented here
provides the opportunity to measure the 3D
thicknessesoffilm
profilesofthin-film-based devices.

2. Method
A new method is proposed to measure
the 3D thickness profiles of metal films

25

using a process of removal of the film. Thismethod consists of surface profile
measurement, film removal, and analignment process. Fig. 1 shows the
proposed steps of the process. Fiducial
marks are fabricated at the area of interest on
the prepared thin film sample (a-b). The top
surface profile of the metal film is measured
with the marks (b). The surface profile of thesubstrate over the same area is measured
after selective removal of film using wet
etching (c). The two profiles are aligned
using a linear transformation by matching
the three fiducial points. The space between
the aligned surface profiles becomes the
thickness profile of the film (d).

(a)
(b)
(c)
(d)
Fig.1 Diagram of film thickness profile
measurement

3. Experiment
Metal films and substrates were prepared
to be measured. Silicon wafers were used as
substrates and nickel (Ni). The films were
deposited by an e-beam evaporator. The
fiducial marks were fabricated on thespecimen using a focused ion beam system(FIB, SII Nanotechnology SMI 3050). Thesurface profiles were measured using atomic
force microscopy (AFM, Bruker Dimension
3100). The measured area was 5 µm × 5 µm.
The lateral resolution of the AFM was 19.5
nm. Wet etching is an appropriate removal
film method since etching selectivity is theproperty generally valued in thin film
technology.
To verify the reliability of the proposed
method, the film thickness was alsomeasured by a spectroscopic ellipsometer(SE MG-1000, Nano View). The thicknessof the films measured using the proposed
method was compared to the thickness
measuredusing
thespectroscopic
ellipsometer with an identical specimen.

4. Conclusion
The measurement results of the thinmetal films are shown in Fig. 2. The
calculated average film thickness was 9.0 nm.
In order to verify the results, the sample wasmeasuredusing
thespectroscopic
ellipsometer. The thickness of the Ni film
was measured to be 8.2 nm with thespectroscopic ellipsometer. The average film
thickness calculated through the proposed
method had an error rate of 8.9 % comparedto the spectroscopic ellipsometer result. The
results demonstrate that the proposed method
is capable of measuring the 3D thickness
profile of the thin metal film with nanometer
resolution.

Fig.2 Measurement results of Ni film. The
thickness, 8.98nm, had error rate of 8.9 %compared to the spectroscopic ellipsometer
result.
References[1] O’Connor B, Haughn C, An K-H, Pipe K
P and Shtein M, Appl. Phys. Lett. 93

26(2008) 223304[2] Zhang X, Choi H, Datta A and Li X, J.
Micromech. Microeng 16 (2006)
900-905[3] Ghim Y-S and Kim S-W, Opt. Exp. 14(2006) 11885-11891[4] Nguyen H V, An I and Collins R W,
Phys. Rev. B. 47 (1993) 3947-3965

O-10

Development of optically controllable electrophoresis with a photoconductive substrate
Taiki NagashimaA, Wataru InamiB, C, and Yoshimasa KawataA, C
A

B

Faculty of Engineering, Shizuoka University, Japan
Division of Global Research Leaders, Shizuoka University, Japan
C
Japan Science and Technology Agency, CREST, Japane-mail: kawata@eng.shizuoka.ac.jp

Abstract
This paper introduces optically controllable electrophoresis with a photoconductive substrate. Thismethod can manipulate microparticles concurrently without any flow channels. We control moving
velocity and direction of microparticles successfully by laser irradiation.
a spatially uniform electric field. The dispersed
particles have electric surface charges, on which
an external electric field exerts an electrostatic
Coulomb force. Velocity and direction of particles
depend on potential gradient.
In this study, we change potential gradient on
the photoconductive substrate by laser irradiationand control moving direction and velocity of
microparticles.

1. Introduction
Micro Total Analysis Systems (µTAS) andLab-on-a-chip have been developed in a medical
and biological applications, and they have been
intensively studied. The systems are expected tohave more quick procedures and higher
functionality.
Objective of this study is to control
microparticles in fluid with laser irradiation. By
combining property of photoconductive substrateandelectrophoresis,
wecanachievemicroparticles operation without flow channel.
We believe that this technique contributes todevelopment of the high functionality analysis
devices.

2. Principle of optically controllable
electrophoresis
Figure 1 shows schematic diagram of
optically controllable electrophoresis. We put afew droplet containing microparticles on thephotoconductive
substrateandgenerateelectrophoresis by applying a voltage to thephotoconductive substrate.
Photoconductive substrate is a kind of
semiconductor, and its conductance is increasedby optical irradiation. When the photoconductive
substrate is applied a voltage, potential gradientarises. On the photoconductive substrate,
potential gradient is reduced in the laser irradiatedarea because conductance of irradiated area isincreased. Bi12SiO20 (BSO) is used as
photoconductive substrate[1, 2].
Electrophoresis is the motion of dispersed
particles relative to a fluid under the influence ofFig. 1. Schematic diagram of principle of opticallycontrollable electrophoresis. In case of negatively
charged microparticles, they move from negativeelectrode to positive electrode along the potential
gradient.

3. Experimental setup
Blue diode laser is used as a light source.
Laser power is from 0.1 mW to 0.5 mW, andwavelength is 405 nm. The applied voltage isfrom 3.0 kV to 5.0 kV. Polystyrene latex particles
are used as microparticles, and the sizes are 7
m and 20 m. We can control irradiated laser
pattern by changing mask pattern and get CCD
camera image with scattering light from particles.

4. Results of electrophoresis on the BSO

27

Figure 2(a) shows particle movements whenline pattern laser is irraiated. Because potential
gradient in the irradiated area becomes gradual,
there is a decrease in the velocity of microparticles
and some microparticles stop movements.
Figure 2(b) shows particle movements whencircular pattern laser is irraiated. Because potential
gradient of the region near the irradiated area
becomes steep, microparticles collect around
irradiated area.
Figure 2(c) shows microparticle separate
operation. Two different sizes of particles are in
the fluid (Particle sizes are 7 m and 20 m).
Verocity of two kinds of particles are different in
irradiation area because quantity of electrification
charges of particle depend on particle size.
Particles of 7 m stop in front of the irradiation
area but particles of 20 m go through.

with laser irradiation
Figure 2 shows CCD images of manipulated
microparticles with laser irradiation of different
pattern. Microparticles move from negativeelectrode to positive electrode without laser
irradiation.

5. Conclusion(a) Line pattern. Particle size: 20 m.

We controlled moving velocity and directionof microparticles successfully by changing laser
irradiation pattern.
We succeeded in separate operation bydifference in size of particles.

6. Future work
In this paper, we introduced microparticle
operation with unsophisticated laser pattern (lineand circular pattern). We will attempt to opticallyoperation with more complicated laser pattern. To
accomplish it, preparing higher-accuracy mask
pattern and optimization of experimental
conditions are necessary.

(b) Circular pattern. Particle size: 20 m.

References[1] R. E. Aldrich, S. L. Hou, and M. L.
Harvill,  ”Electrical  and  Optical  properties  of  Bi12SiO20 ”  J. Appl. Phys., 42, (1971) 493．
[2] M.   Peltier   and   F.   Micheron,   “   Volume  hologram recording and charge transfer
process in Bi12SiO20 and Bi12GeO20,  ”J. Appl.
Phys., 48, (1977) 3683．

(c) Separate operation. Particle size: 7 and 20 m.
Fig. 2. CCD images of manipulated microparticles
with laser irradiation of different pattern. Particle
movements vary with the laser irradiation. Laser
power is from 0.1 mW to 0.5 mW, and wavelength is405 nm. Applied voltage is from 3.0 kV to 5.0 kV.

28

O-11

Image reconstruction for portable digital holographic
microscopy using a glass phase shifter
JaeHyeong Park, Janghyun Cho, Sungbin Jeon, Kyungsoo Lee
Sang-Jo Lee, Byung-Kwon Min*
Department of Mechanical Eng, Nano Manufacturing & Mechatronics, Yonsei University,
308 Industry-University Research Center, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Korea
TEL&FAX : +82-2-2123-6611*
e-mail: bkmin@yonsei.ac.kr

Abstract
Phase shifting in digital holography is used to obtain holographic images clearly andquickly. Because of size and price, conventional phase shifter is not appropriate for portable
digital holographic microscope. And then we propose glass phase shifter which is inexpensive
and small. We compare Image reconstruction using the conventional with glass. It is shownthat glass can be used as phase shifter for portable digital holographic microscope.

1. Introduction
Digital holography is used for a wide
range of applications. A lot of techniques
deal with holographic microscopy. Digitalholographic microscope (DHM) using phaseshifter within reference beam path can obtainhigh-resolution images without noise andcalculate numerical reconstruction quickly.
In many current DHM, wave plate, phase
SLM, and piezo actuator are used as a phaseshifter. In particular, because it can be
precise control using the same phase shifter
the case of phase SLM and piezo actuator
has been studied in a lot of digitalholographic systems. The case of digitalholography using phase shifting the DC
component and the imaginary components of
the image compared to the general decline,
and with the addition of some algorithmic it
is possible to remove these almost
completely.

Fig. 1. The schematic view of experimental
setup.

29

But these phase shifters are large andexpensive, so in the current phase shifter wasdeveloped to use a portable DHM
inappropriate. Therefore, the development ofa phase shifter for portable DHM is required.
Because glass is inexpensive and easy
processing suitable, glass has the advantageof the portable DHM. In this paper, thepossibility of flat glass used as a phaseshifter is analyzed.

2. Experiment
In this paper, as shown in Fig. 1 By using
a beam spliter which separate the reference
beam and object beam off-axis digitalholographic microscopy methods were used.
ND:yag laser (=532nm), CCD image
sensor (pixel size : 3.45m x 3.45 m )and a test target (USAF 1951 Chart) wereused.
First, we put a obstacle on the object
beam path, and then obtain the reference
image without the use of glass. Second, we
put away the obstacle, and then obtain theinterference image between the reference
beam and object beam. Finally, we put a flatglass which has random thickness on thereference beam path, and then obtain theinterference image between the phase shiftedreference beam and object beam. Obtained
hologram
imagesarenumericallyreconstructed by using simple direct
extraction of unknown phase shift algorithm

Fig. 2 holograpic images.

with LabVIEW (National Instrument). [1]3. Results and Discussion
Fig. 2 (a), (b), (c) are respectively
reference image, interference image, phaseshifted interference image using glass phaseshifter. Fig. 3 (a), (b) are reconstructed
images using phase SLM and flat glass asphase shifter respectively.
Glass phase shifter and the original wereable to confirm that a similar image
reconstruction quality. Therefore, we
demonstrate that glass phase shifter can beused in a portable DHM.

Fig.3 Image reconstruction result using (a) phase
SLM, (b) flat glass.

4. Conclusion
In this research we suggest phase shifter
for portable DHM. To use low-priced andlighter phase shifter we certify that glass isgood phase shifter for portable DHM.

30

Reference[1] X. F. Xu, L. Z. Cai, Y. R. Wang, X. F.
Meng, W. J. Sun, H. Zhang, X. C. Cheng,
G. Y. Dong, and X. X. Shen, Optics
Letters 33 (2008) 8

O-12

Measurement of electron transmittance of a luminescent thin filmwith a high electron stopping power layer
Takuya Miyazawa1, Yotaro Nishimura1, Wataru Inami2,3, Yoshimasa Kawata1,3
1Faculty of Engineering, Shizuoka University, Japan
2
Division of Global Research Leaders, Shizuoka University, Japan
3
Japan Science and Technology Agency, CREST, Japan
E-mail: kawata@eng.shizuoka.ac.jp

Abstract
Electron beam may damage specimens at electron beam excitation assisted optical
microscope observation. In this paper, we sputtered Au on Si3N4 film for stopping electron beam
which damage living biological specimens, and measured electron transmittance of this film. Au
sputtering is effective to reduce electron transmittance, but there is the difference between
measured and calculated data. This major cause is secondary electron emission from Au film.

1. Introduction
We propose electron beam excitation
assisted optical (EXA) microscope in whichelectron beam focused on a luminescent thinfilm excites nanometric light source near a
specimen [1]. This luminescent film is muchthin so that electron beam may transmit
through this film. Electron beam may damage
the specimen. This is a problem to observe
dynamic process of living biological
specimens. The luminescent film which canstop electron beam is required.
In this study, we cover sputtering film for
stopping electron on luminescent film, andthen measure of electron transmittance of thisfilm in 1~10 eV.

the scanning electron microscope (SEM,
JSM-6390, JEOL) is used. The accelerated
electron is focused on luminescent film
surface by field lens. Incident electron ismeasured by the detector fixed on SEM, andtransmitted electron is measured by Faradaycup (FC) on specimen mount. The ratio oftransmitted electron to incident electron iselectron transmittance of the film.

2. Luminescent film with a highelectron stopping layer
We coated Au layer on Si3N4 film byradio-frequency sputtering system (CFR-700,
SANYU ELECTRON). Au has high electron
stopping power and can be sputtered without
oxidation. Si3N4 film (thickness: 50 nm) isused in EXA microscope as a luminescentfilm.
Fig. 1

3. Setup of electron transmittancemeasurement
Figure 1 shows schematic diagram ofexperimental setup of electron transmittancemeasurement. In this experiment,

31

Setup of electron transmittancemeasurement

4. Experimental results and discussion
Figure 2 shows electron transmittance as
dependent on acceleration voltage; blue line
is measured data of Si3N4 (which thickness is
50 nm) without Au layer, red line is Si3N4
with Au layer which thickness is 20 nm,
green line is with Au layer which thickness is
40 nm, and purple line is calculated data with
Au layer which thickness is 20 nm by Monte
Carlo simulation (MC).
electron transmittance [%]

110
100
90
80
70
60
50
40
30
20
10
0

without Au
with Au 20 nmwith Au 40 nm
MC (Au 20 nm)
0

2

4

6

8

10

acceleration voltage [kV]Fig. 2

Electron transmittance of each film

5. Conclusion

electron transmittance [%]Electron beam is stopped to 1.5 kVwithout Au, 2.0 kV with Au 20 nm, and 3.0
kV with Au 40 nm. It seems that as Au is
thicker luminescent film has a higher electron
stopping power. And, electron transmittanceis 79 % without Au, 35 % with Au 20 nm,
and 1.2 % with Au 40 nm at 3 eV. Electrontransmittance is reduced by sputtering Au.
About Si3N4 with Au 20 nm, there isdifference up to 50 % between measured dataand calculated data.
100
90
80
70
60
50
40
30
20
10
0

measured data
calculated data with SE
calculated data

We sputtered Au on Si3N4 film for
stopping electron beam which damage living
biological specimens, and measured electrontransmittance of this film. And, Au sputtering
is effective to reduce electron transmittance,
but there is the difference between measured
and calculated data. This major cause issecondary electron emission from Au film.
Secondary electron energy is up to about
50 eV, but transmitted electron has a few kilo
electron volts (keV). So, we have a need toconsider the effect on damage to the living
cells by the difference of energy electrons
have. Additionally, luminescent film with theother materials which have a high electron
stopping power is had to be measured.

References

0

2

4

6

8

[1] W. Inami, K. Nakajima, A. Miyakawa,and Y. Kawata, “Electron beam excitation
assisted
opticalmicroscope
withultra-high resolution,” Opt. Exp. 18,
12897-12902 (2010).

10

accelerated voltage [kV]Fig. 3This difference is thought to be due tosecondary electron from Au layer. FC used inthis experiment can suppress secondary
electron outflow from collector, but not
inflow from Au layer. Figure 3 showselectron transmittance with Au 20 nm whichis measured data, calculated data, andcalculated data added secondary electron
emission from Au layer.
The approach of secondary electron
calculation is roughly. In this study,
secondary electron emission is calculated bysecondary electron coefficient dependent on
primary electron energy and electron energy
in position of about 5 nm from the end of Au
layer. This length is the secondary electron
escape depth of Au.
At high acceleration voltage, calculated
data added secondary electron from Au layer
fit in measured data. Thus, the major cause of
the difference between measured andcalculated data is secondary electron from Au
film.

Comparison of electron transmittance of
Si3N4 with Au 20 nm

32