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CHAPTER 8

THREE-DIMENSIONAL NANOSTRUCTURE FABRICATION BY

FOCUSED-ION-BEAM CHEMICAL-VAPOR-DEPOSITION

Shinji Matsui

University of Hyogo 3-1-2 Koto, Kamigori, Ako, Hyogo, Japan

Three-dimensional nanostructure fabrication has been demonstrated by

30 keV Ga+

focused-ion-beam chemical-vapor-deposition (FIB-CVD)

using a phenanthrene (C14H10) source as a precursor. Microstructure

plastic arts is advocated as a new field using micro-beam technology,

presenting one example of micro-wine-glass with 2.75 m externaldiameter and 12 m height. The deposition film is a diamondlike

amorphous carbon. A large Youngs modulus that exceeds 600 GPa

seems to present great possibilities for various applications.

Producing of three-dimensional nanostructure is discussed. Micro-coil,

nanoelectrostatic actuator, and nano-space-wiring with 0.1 m

dimension are demonstrated as parts of nanomechanical system.

Furthermore, nanoinjector and nanomanipulator are also fabricated as a

novel nano-tool.

1. Introduction

Two-dimensional nanostructure fabrication using electron-beam

(EB) and focused-ion-beam (FIB) has been achieved and applied to make

various nanostructure devices such as single electron transistors and

MOS transistors with nanometer gate-length. Ten-nm structures are able

to be formed by using a commercial available EB or FIB system with

5-10 nm beam diameter and high-resolution resist [1]. In this way,

it is considered that the technique of two-dimensional nanostructure

fabrication has been established. Outlook on three-dimensional

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fabrication, there are three techniques using laser, EB, and FIB Chemical

Vapor Deposition (CVD). Compared to three-dimensional fabrication of

laser-CVD, FIB and EB-CVD are superior to laser-CVD [2] in point of aspatial resolution and a beam-scan control. Koops et al. demonstrated

some applications such as AFM tip and field emitter by using EB-CVD

[3]. Blauner et al. demonstrated pillars and walls with high aspect ratios

by using FIB-CVD [4].

The deposition rate of FIB-CVD is much higher than that of EB-

CVD due to factors such as the difference of mass between electron and

ion. Furthermore, a smaller penetration-depth of ion compared toelectron allows to make a complicated 3-dimensional nanostructures. For

example, when we make a coil nanostructure with 100 nm linewidth,

electrons with 10-50 keV pass the ring of coil and reach on the substrate

because of large electron-range (over a few m), so it may be difficult to

make a coil nanostructure by EB-CVD. On the other hand, as ion range

is less than a few ten-nm, ions stop inside the ring. So far the

complicated nanostructures using FIB-CVD have not been reported. This

presents a complicated 3-dimensional nanostructure fabrication using

FIB-CVD.

2. Three-Dimensional Nanostructure Fabrication

We used a commercially available two FIB systems (SMI9200,

SMI2050, SII Nanotechnology Inc.) with a Ga+

ion beam operating at

30 keV. The FIB-CVD was done using a precursor ofphenanthrene

(C14H10) as the source material. The beam diameter of SMI9200 was

about 7 nm and that of SMI2050 was about 5 nm. The SMI9200 system

was equipped with two gas sources in order to increase the gas pressure.

The top of the gas nozzles faced each other and were directed at the

beam point. The nozzles were set at a distance of 40 m from each other

and positioned about 300 m above the substrate surface. The inside

diameter of a nozzle was 0.3 mm. The phenanthrene gas pressure duringpillar growth was typically 5x10

-5Pa in the specimen chamber, but, the

local gas pressure at the beam point was expected to be much higher. The

crucible of the source was heated to 85C. The SMI2050 system, on the

other hand, was equipped with a single gas nozzle. The FIB is scanned to

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Three-Dimensional Nanostructure Fabrication 353

write the desired pattern by a computer control and the ion dose is

adjusted to deposit a film of the desired thickness. The experiments were

carried out at room temperature on a silicon substrate.The characterization of deposited film was performed by

observation of transmission electron microscope (TEM) and measuring

of Raman spectra. A carbon thin film with 200 nm thickness was

deposited on a silicon substrate by 30 keV Ga+

FIB using aphenanthrene

precursor gas. The cross-section structures and electron diffraction

patterns were observed by using a 300 kV TEM. As a result, there were

no crystal structures in TEM images and diffraction patterns. It isconcluded that the deposited film is amorphous carbon (a-C).

Raman spectra of a-C films were measured at room temperature with

514.5 nm line of an argon ion laser. The Raman spectra were recorded by

a monochromator equipped with a CCD multi-channel detector. Raman

spectra were measured at 0.1-1.0 mW to avoid thermal decomposition of

the samples. A relatively sharper Raman band at 1550 cm-1

and a broad

shoulder band at around 1400 cm-1

are observed in the spectra excited by

a 514.5 nm line. Two Raman bands were plotted after the Gaussian line

shape analysis. Raman bands at 1550 cm-1

and 1400 cm-1

originate in

trigonal (sp2) bonding structure of graphite and tetrahedral (sp

3) bond

structure of diamond. This result indicates that a-C film deposited by

FIB-CVD is diamondlike amorphous carbon (DLC) which have attracted

attention because of their hardness, chemical inertness, and optical

transparency.

2.1. Fabrication Process

Beam-induced chemical vapor deposition (CVD) is widely used in

the electrical device industry in repairing chips and masks. This type of

deposition mainly done on two-dimensional (2D) patterning features, but

it can also be used to fabricate a three-dimensional (3D) object. Koops

et al. demonstrated a nano-scale structure 3D construction [3] usingelectron-beam-induced amorphous carbon deposition applied to a micro

vacuum tube. In contrast, focused-ion-beam (FIB) induced CVD seems

to have big advantages and potential in the fabrication of 3D nano-

structures [4-6]. The key issue in making such 3D-work is the short

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penetration depth of the ions (a few nm) in the target material, where the

penetration depth of the ions is much shorter compared to that of the

electrons (several hundreds of microns). This short penetration depthreduces the dispersion area of the secondary electrons, and thus the

deposition area is tightly limited to within about several tens nanometers.

Usually, a 3D structure contains overhang structures and hollows.

Gradual position-scanning of the ion beam during the CVD process

causes the position of the preferentially growing region around the beam

point to shift. When the beam point reaches the edge of the wall,

secondary electrons appear at the side of the wall and just below the topsurface. The DLC then starts to grow laterally. The width of the vertical

growth is also about 80 nm. Therefore, combining the lateral growth

mode with the rotating beam scanning, 3D structures having a rotational

symmetry like a wineglass are obtained.

Fig. 1. Fabrication process for three-dimensional nanostructure by FIB-CVD.

Three-dimensional structure fabrication process by FIB-CVD is

illustrated in Fig. 1 [7]. In FIB-CVD processes, beam is scanned at digital

mode. First, a pillar is formed on the substrate by fixing a beam-position

(position 1). After that, the beam-position is moved within a diameter ofpillar (position 2) and then fixed until the deposited terrace thickness

exceeds an ion-range which is a few ten nm. This process is repeated to

make three-dimensional structures. The key point to make three-

dimensional structures is to adjust a beam-scan-speed as remaining ion-

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beam within the deposited terrace which means that the terrace thickness

exceeds an ion-range. The growth conditions of x and y-directions are

controlled by both beam-deflectors. The growth of z-direction isdetermined by a deposition rate, that is, a height of structure is

proportional to an irradiation-time when a deposition rate is constant.

Fig. 2. (a) Micro-wine-glass with 2.75 m external diameter and 12 m height. (b)

Micro-coil with 0.6 m coil-diameter, 0.7 m coil-pitch, and 0.08 m linewidth. (c)

Micro colossem.

Fig. 3. Micro-wine-glass with 2.75 m external diameter and 12 m height on a human

hair.

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We intend to open up microstructure plastic arts as a new field using

FIB-CVD. To demonstrate the possibility, a micro-wine-glass was

created on a Si substrate and a human hair as a work of microstructureplastic arts as shown in Figs. 2(a) and 3. A micro-wine-glass with 2.75 m

external diameter and 12 m height was formed. Fabrication time was

600 s at 16 pA beam current. The beautiful micro-wine-glass gives us

expectations of opening up microstructure plastic arts. The micro-

coliseum and leaning tower of Pisa were also fabricated on a Si substrate

as shown in Figs. 2(c) and 4.

Fig. 4. Leaning tower of Pisa.

Various micro-system parts were fabricated by FIB-CVD. Figure 2(b)

shows a micro-coil with 0.6 m coil-diameter, 0.7 m coil-pitch, and

0.08 m linewidth. Exposure time was 40 s at 0.4 pA beam current. A coil-

pitch is able to change by controlling a growth speed with ease. Reducing

a diameter of micro-coil, a micro-drill was formed. A diameter, pitch, and

height of the micro-coil are 0.25, 0.20, and 3.8 m, respectively. Exposure

time was 60 s at 0.4 pA beam-current. The results show that FIB-CVD is

one of the promising techniques to make parts of micro-system, although

those mechanical performances have to be measured.

2.2. Three-Dimensional Pattern Generating System

To fabricate the 3-D structure, we used deposition of a source gas by

ion beam assist. The 3-D structure fabricates as a multi layer structure. In

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this 3-D pattern-generating system, a 3-D model designed by a 3-D

CAD system (3-D DXF format) is needed to manufacture the 3-D

structure as the first step. There are no specializations of structure shapewithout cernuous structure shaped like pendulum. The 3-D CAD model,

which is a surface model, is cut into several slices, as shown in Fig. 5.

The thickness of slices depends on the resolution of the z direction

(vertical direction). Second, the slice data are divided in the x and y

directions (horizontal directions) to create the scan data (voxel data). To

fabricate the overhang structure, ion beam must be irradiated in optimum

order. If the ion beam is irradiated to a voxel located in midair without asupport layer, the voxel deposits on the substrate. Therefore, the priority

of irradiation is determined as number 1 to number 7 of Fig. 5.

Fig. 5. Data flow of 3-D pattern-generating system for FIB-CVD.

The scan data and blanking signal are then made from the scan order

of priority, set dwell time, interval time, and irradiation pitch. These

parameters are calculated from beam diameter, x-y resolution, and z

resolution of fabrication. The z resolution is proportional to dwell time

and inverse proportional to irradiation pitch squared. The scan data are

input to the beam-deflector of the FIB-CVD in synchronization with theblanking data. The blanking signal controls the dwell time and interval

time of the ion beam.

Figure 6 shows a 3-D CAD model and SIM image of the Star Trek

spaceship Enterprise NCC-1701D fabricated by FIB-CVD at 10~20 pA

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[8]. The nano-spaceship is 8.8 m long and about a 1:100,000,000 scale

on silicon substrate. The dwell time (td), interval time (ti), irradiation

pitch (p), and total process time (tp) were 80 s, 150 s, 2.4 nm, and2.5 h, respectively. The horizontal overhang structures was fabricated

successfully.

Fig. 6. Star Trek, spaceship Enterprise NCC-1701Ds micro model, 8.8 m long.

Figure 7 shows the artificial nano T4 Bacteriophage, which is a

virus like the robot in the living body, fabricated by FIB-CVD on Si

surface. Size of the artificial nano T4 Bacteriophage is about ten

times as large as the real virus.

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Fig. 7. T-4 Bacteriophage

3. Nanoeletromechanics

3.1. Youngs Modulus Measurement

An evaluation of the mechanical characteristics of suchnanostructures are needed as the basis of the material physics. Buks and

Loukes reported a simple but essential technique [9] for measuring the

resonant frequency of nano-scale objects by using a scanning electron

microscope (SEM). The detector of secondary electrons in the SEM can

respond up to around 4 MHz, thus the vibration of the sample is

measured as the oscillatory output signals of the detector. Buks and

Loukes used this technique to evaluate the Casimir force attractedbetween the two parallel beams fabricated on an nano scale. We

evaluated the mechanical characteristics of DLC pillars in terms of the

Youngs modulus determined by using resonant vibration and the SEM

monitoring technique [10, 11].

The system set-up for monitoring mechanical vibration is shown in

Fig. 8(b). There were two ways of measuring the pillar vibrations. One

was active measurement, where the mechanical vibration was induced by

a thin piezo-electric device, 300 m thick and 3 mm square. The piezo

device was bonded to the sidewall of the SEMs sample holder with

silver-paste. The sample holder was designed to observe cross sections in

the SEM (S5000, Hitachi) system. Therefore, the pillars vibration was

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observed as a side view image as shown in Fig. 8(a). The vibrating

frequency was the range of 10 kHz up to 2 MHz, which is much faster

than the SEM raster scanning speed. Thus the resonant vibration of thepillars can be taken as the trace of the pillars vibration in the SEM

image. The resonant frequency and amplitude were controlled by

adjusting the power of the driving oscillator.

Fig. 8. (a) SEM image of the vibration. The resonant frequency was 1.21 MHz.

(b) Schematic diagram of the vibration monitoring system.

The other way of measuring pillars vibrations is passive

measurement using a spectrum analyzer (Agilent, 4395A), where the

vibration seemed to mainly be induced by a environmental noise from

rotary pumps and air conditioners. Some parts of the vibration would be

resulted from the spontaneous vibration associated with thermal

excitations [9]. Because of such excitation and residual noise, pillars on

the SEM sample holder always vibrated at a fundamental frequency,even if the noise isolation is done in the SEM system. The amplitude of

such spontaneous vibration was in the order of a few nanometer at the

top of the pillar, and the high-resolution SEM can easily detect it at a

magnification typically of 300,000.

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We arranged several pillars that had varying diameters and lengths.

The DLC pillars having the smallest diameter of 80 nm were grown

using point irradiation. While we used two FIB systems for pillarfabrication, slight differences in the beam diameter of the two systems

did not affect the diameter size of the pillars. Larger diameter pillars

were fabricated using an area-limited raster scan mode. The raster scan in

a 160-nm-square region produced a pillar having about a 240-nm-square

cross section, and a 400-nm-square scan resulted in a pillar having a

480-nm-square cross section. The typical SEM image during resonance is

shown in Fig. 8(a). The FIB-CVD pillars seemed very durable againstthe mechanical vibration. This kind of measurement usually requires at

least 30 min including a spectrum analysis and photo-recording, but the

pillars still survived without any change in the resonant characteristics.

This durability in DLC pillars will be useful in nano-mechanical

applications.

The resonant frequency f of the pillar is defined by Eq. (1) for a

pillar with a square cross-section and Eq. (2) for that with a circular

cross-section:

2

2 122square

a Ef

L

= (1)

2

2

162circular

a Ef

L

= (2)

where a is the width of the square pillar and/or the diameter of the

circular-shaped pillar,L is the length of the pillar, is the density, andE

is Youngs modulus. The coefficient ofdefines the resonant mode and

the =1.875 at the fundamental mode. We used Eq. (1) for pillars 240 nm

wide and 480 nm wide, and Eq. (2) for pillars grown by point-beam

irradiations. The resonant frequency in terms of Youngs modulusdepending on the ratio of the pillar diameter divided by the squared

length is summarized in Fig. 4. All of the pillars evaluated in this

figure were fabricated using the SMI9200 FIB system in rapid growth

conditions. Typical growth rates were about 3 m/min to 5 m/min. for

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the 100-nm-diameter and 240-m-wide pillars, and 0.9 m/min. for the

480-nm-wide pillars. In the calculation of Fig. 9, we assumed that the

density of the DLC pillars was about 2.3 g/cm3

, which is almost identicalto that of graphite and quartz. The inclination of the line in Fig. 9

indicated the Youngs modulus for each pillar. The Youngs modulus of

each pillar was distributed in a range from 65 GPa to 140 GPa, which is

almost identical to that of normal metals. A wider pillar tended to have a

larger Youngs modulus.

Fig. 9. Resonant frequency dependence on the pillar length.

We found that the stiffness becomes significantly stiffer as the local

gas pressure decreased as shown in Fig. 10. While the absolute value ofthe local gas pressure at the beam point is very difficult to determine, we

found the growth rate can be useful as a parameter in terms of the local

gas pressure to describe the pressure dependence on the Youngs modulus.

All data points indicated in the Fig. 10 were obtained by pillars grown

using point irradiation. Thus the pillar diameters were slightly distributed

around 100 nm but did not exceed 5%. A relatively lower gas pressure

maintaining good uniformity was obtained using a single gas nozzle andgas reflector. We use a cleaved side wall of Si tips as the gas reflector,

which was placed 10-50 m away from the beam point so as to be facing

to the gas nozzle. The growth rate was controlled by changing the

distance to the wall. While there is a large distribution of data points, the

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stiffness of the pillar tended to become stiffer as the growth rate

decreased. Two curves in Fig. 10 represented data points obtained under

beam current of 0.3 pA (open circle) and 1 pA (solid circle), respectively.Both curves showed the same tendency where the saturated upper levels

of the Youngs modulus was different for each ion current at lower gas

pressure(lower growth rate). It should be noted that some of the pillars

Youngs modulus exceeded 600 GPa, which is of the same order of

tungsten-carbide. In addition, those estimation assumed the pillar density

to be 2.3 g/cm3, however, a finite amount of Ga was incorporated with

the pillar growth. If the calculation will take account of the increase ofpillar density by the Ga concentration, Youngs modulus will exceed

800 GPa. Such high Youngs modulus is almost closed to that of carbon

nano-tube and natural diamond crystal. We think that such high Youngs

modulus is presumably due to surface modification caused by the direct

ion impact.

Fig. 10. Youngs modulus dependence on the growth rate.

In contrast, when the gas pressure was high enough to achieve a

growth rate of more than 3 m/min, pillars became soft but the change ofthe Youngs modulus was small. The uniformity of Youngs modulus as

shown in Fig. 9, presumably resulted from the fact that the growth

condition was in this insensitive region, where the supplement of source

gas limited the pillar growth.

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3.2. Free-Space-Nanowiring

All experiments were carried out in a commercially available FIB

system (SMI9200: SII NanoTechnology Inc) using a beam of 30 kV Ga+

ions. The beam is focused to a spot size of 7 nm at a 0.4 pA beam current,

and it is incident perpendicular to the surface. The pattern drawing

system of CPG (CPG-1000: Crestec Co) was added to the FIB apparatus

to draw any patterns Using the CPG, a beam scanning control is possible

such as scanning speed, x-y direction, and blanking of a beam, and the

3D free-space-nanowiring can be fabricated [12].

Fig. 11. Fabrication process of DLC free-space-wiring using both FIB-CVD and CPG.

Figure 11 illustrates the free-space-nanowiring fabrication process

using both FIB-CVD and CPG. When phenanthrene (C14H10) gas or

tungsten hexacarbonyl [W(CO)6] gas, which is a reactant organic gas, are

evaporated from a heated container and injected into the vacuum

chamber by a nozzle located 300 m above the sample surface at an

angle of about 45 deg with respect, the gas density of the C14H10 orW(CO)6 molecules increases on a substrate near a gas nozzle. The nozzle

system served to create a local high-pressure region over the surface. The

base pressure of the sample chamber is 210-5

Pa and the chamber

pressure after introducing C14H10 and W(CO)6 as a source gas are 110-4

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and 1.510-3

Pa, respectively. If a Ga

ion beam is irradiated onto the

substrate, C14H10 or W(CO)6 molecules adsorbed on the substrate surface

are decomposed, and carbon (C) are mainly deposit on the substratesurface. The growth direction of deposition can be freely determined by

controlling the scanning direction of a beam. Deposited material using

C14H10 gas was diamondlike carbon, which was confirmed by Raman

spectra and it had a very large Youngs modulus of 600 GPa [7, 10].

After two walls were formed in Fig. 11, free-space-nanowiring was

grown by adjusting a beam scanning speed. The ion beam was used at

30 kV Ga

+

FIB, and the amount of irradiation current was 0.8-2.3 pA. Thex and y scanning directions and beam scanning speed were controlled by

CPG. The z direction height was proportional to an irradiation time. A

growth of deposition occurs horizontally by scanning a beam at a certain

fixed speed in the direction of a plane. However, if the beam scanning

speed is faster than the nanowiring growth speed, it grows downward or

fall, and conversely if the scanning speed is slower, it grows up slantingly.

That is, it is very important for growing up a nanowiring into a horizontal

direction to control the beam scanning speed. It turns out that the optimal

beam scanning speed to make the nanowiring, which grows up to be a

horizontal direction using two C14H10 gas guns, is about 190 nm/s. The

expected pattern resolution by FIB-CVD is around 80 nm, because both

primary Ga+

ion and secondary-electron scattering are found around

20 nm [10, 13].

Figures 12 and 13 show the examples of free-space-nanowirings

fabricated by FIB-CVD and CPG. All structures were fabricated using

C14H10 gas as a precursor gas.

Figure 12(a) shows nano-bridge free-space-wirings. The growth time

was 1.8 min, and the wiring width was 80 nm. Figure 12(b) shows free-

space-wirings of parallel resistances. The growth time was 2.8 min, and

the wiring width was also 80 nm.

Figure 13(a) shows free-space-wiring grown into sixteen directions

from the center. Figure 13(b) shows a scanning-ion-microscope (SIM)image of an inductance (L), a resistance (R), and a capacitor (C) parallel

circuit structure with free-space-nanowirings. A coil structure was

fabricated by a circle scanning of Ga+

FIB. These growth times of L, R,

and C structures were about 6, 2, and 12 min, and the all nanowiring

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width was about 110 nm. From these structures, it is possible to fabricate

arbitrary nanowirings at arbitrary places by using FIB-CVD and CPG.

And these results indicate that various circuit structures can be formed bycombining L, C, and R.

Fig. 12. (a) DLC free-space-wiring with a bridge shape. (b) DLC fre-space-wiring with

parallel resistances.

Fig. 13. (a) Radial DLC free-space-wiring grown into 16 directions from the center. (b)

Scanning ion microscope (SIM) micrograph of an inductance (L), a resistance (R), and a

capacitor (C) structures.

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Free-space-wiring structures were observed by 200 keV TEM. The

analyzed area was 20 nm . Figures 14(a) and 14(b) show TEM images

of DLC free-space-wiring and pillar. It became clear from these EDXmeasurements that the dark part (A) of Fig. 14(a) corresponds to the Ga

core, and the outside part (B) of Fig. 14(a) corresponds to amorphous

carbon. In this way, a free-space-wiring consists of amorphous carbon

containing a Ga core in the wiring. The center position of the Ga core is

located below the center of the wiring. However, in the case of the DLC

pillar, the Ga core is located in the center of the pillar. This result

indicates that a center position of the Ga core is different between theDLC free-space-wiring and pillar. To evaluate the difference, the Ga core

distribution in free-space-wiring was observed in detail by TEM. The

center position of the Ga core is about 70 nm from the top, which is

20 nm below the center of the free-space-wiring. We calculated an ion

range of 30 kV Ga ions into amorphous carbon by TRIM (Transport of

Ions in Matter), of 20 nm. The calculation indicates that the displacement

of the Ga core center position corresponds to the ion range.

Fig. 14. TEM images of (a) DLC free-space-wiring and (b) DLC pillar.

The electrical properties of free-space-nanowiring fabricated by FIB-

CVD using a mixture gas of C14H10 and W(CO)6 were measured.

Nanowirings fabricated on Au electrode by using C14H10 and W(CO)6 as

a source gas. Au electrodes were formed on a 0.2 m-thick SiO2 on Si

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substrate by EB lithography and lift-off process. Two-terminal electrode

method was used to measure the electrical resistivity of the nanowiring.

Figure 15(a) shows the nanowiring fabricated by using only C14H10source gas. This growth time was 65 s and the wiring width was 100 nm.

Next, W(CO)6 gas was added to C14H10 gas as a mixture gas containing a

metal to obtain a lower electrical resistivity. Figures 15(b), 15(c), and

15(d) correspond to the order of increasing W(CO)6 content in a mixture

gas. The W(CO)6 content rate was controlled by sublimation temperature

of C14H10 gas. Increasing W(CO)6 content, the nanowiring growth time

and width become longer: (b) was 195 s and 120 nm, (c) was 237 s and130 nm, and (d) was 296 s and 140 nm. Finally, we tried to fabricate a

free-space-nanowiring using only W(CO)6, but did not obtain a

continuous wiring, because the deposition rate in the case of using

W(CO)6 source gas was very slowly.

Fig. 15. Electrical resistivities measurement for nanowirings. Electrical resistivity was

calculated byIVcurve. Elemental contents C, Ga, W were measured by SEM-EDX.

The electrical resistivity of Fig. 15(a) fabricated by using only C14H10source gas was 110

2 cm. The elemental contents were 90% C and

10% Ga, which were measured by a spot beam of SEM-EDX.IVcurves

(b), (c), and (d) correspond to the order of increasing W(CO)6 content in

a mixture gas. Increasing W(CO)6 content, the electrical resistivity

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decreases as shown inIVcurves (b)(d). Moreover, Ga content rate was

also increasing because nanowirings growth time became slower, that is,

the irradiation time of Ga+

FIB became longer. The electrical resistivityofIV curves (b), (c), and (d) were 16, 410

-2, and 210

-2 cm,

respectively. The electrical resistivity of (e), which was fabricated by

using only W(CO)6 source gas was 410-4

cm. The increasing of Ga

and W metallic content corresponds to decreasing of electrical resistivity

as shown in SEM-EDX measurement results of Fig. 15. These results

indicate that a lower resistivity is caused by increasing metallic content.

Electron holography is useful technology for direct observation ofelectrical and magnetic fields at nanoscale, and also has an efficient

property of showing useful information by detecting the phase shift of

the electron wave due to the electrical and magnetic field. The technique

necessarily needs an electron biprism, which plays an important role of

dividing electron wave into reference wave and objective wave. The

biprism is composed of one thin filament and two ground electrodes.

Fig. 16. Electron biprism fabricated by FIB-CVD.

It is important to fabricate a filament as narrow as possible to obtain

an interference fringe with a high contrast and good fringe quality.

However, fabricating the filament with a diameter below 500 nm is very

difficult, because a conventional electron biprism is fabricated by pulling

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a melted glass rod by hand.To overcome this problem, we introduce a

new fabrication technique of the electron biprism using FIB-CVD, and

evaluate the characteristics of the new biprism.Figure 16 shows an SEM micrograph of the FIB-CVD biprism. We

successfully fabricated DLC wiring with smooth surface in between W

rods by free-space-wiring fabrication technology of FIB-CVD. The

80-nm DLC thin wiring works as the filament of the biprism. The

diameter and length of the filament are 80 nm and 15 m, respectively.

Fig. 17. Interference fringes and corresponding fringe profiles. (a) obtained using the

biprism with diameter of 80 nm, and (b) obtained using the biprism with diameter of

400 nm.

Figure 17 shows the interference fringes obtained using the biprism

with a filament of (a) 80-nm diameter and (b) 400-nm diameter, andcorresponding fringe profiles. The applied-prism voltages were 20 V,

respectively. The filament with 400-nm-diameter, close to the standard

size used in the conventional electron biprism, was fabricated by Pt-

sputter coating onto the 80-nm-diameter filament. The interference

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fringes were successfully obtained. Moreover, an interference region of

the fringe obtained using the biprism with the 80-nm-diameter filament is

larger than that of the fringe obtained using the biprism with the 400-nm-diameter filament. These results demonstrate an adequacy of the thin

filament fabricated by FIB-CVD, and the new biprism will be very useful

for an accurate observation with a high contrast and good fringe quality

in electron holography.

Fig. 18. Fabrication process of 3D nano-electrostatic actuators.

3.3. Nanoelectrostatic Actuator

The fabrication process of 3-D nano-electrostatic actuators and

manipulators is very simple [14]. Figure 18 shows the fabrication process.

First, a glass capillary (GD-1: Narishige Co.) was pulled using a

micropipette puller (PC-10: Narishige Co.). The dimensions of the glass

capillary are 90 mm in length and 1 mm in diameter. In this process, weobtained a 1-m-diameter tip of the glass capillary. Next, we carried

out Au coating on the glass capillary surface by DC sputtering. Au

thickness was approximately 30 nm. This Au coating serves as the

electrode that controls the actuator and manipulator. Then, the 3-D nano-

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electrostatic actuators and manipulators were fabricated by FIB-CVD.

This process was carried out in a commercially available FIB system

(SIM9200: SII NanoTechnology Inc.) with a Ga+

ion beam operating at30 keV. FIB-CVD was carried out using a precursor ofphenanthrene

(C14H10) as a source material. The beam diameter was about 7 nm. The

inner diameter of each nozzle was 0.3 mm. The phenanthrene gas

pressure during growth was typically 5x10-5

Pa in the specimen chamber.

The Ga+

ion beam could be controlled by transmitting CAD data of the

arbitrary structures to the FIB system.

Fig. 19. Coil-type electrostatic actuator. (a) SIM image of a coil-type electrostatic

actuator fabricated on the tip of Au-coated glass capillary. (b) Illustration of moving

principle.

A coil-type electrostatic actuator was fabricated by FIB-CVD.

Figure 19(a) shows the SIM image of the coil-type electrostatic actuator

fabricated at 7 pA and 10 min exposure time. Figure 19(b) shows the

movement principle of this actuator. The movement principle of thisactuator is very simple. The driving force is the repulsive force induced

by electric charge accumulation. This electric charge can be stored in this

coil structure by applying the voltage onto a glass capillary. This coil

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structure expands and contracts due to charge repulsion, as shown in

Fig. 19(b). Figure 20 shows the applied voltage dependence of coil

expansion. The length of the coil expansion is defined as the distance ain the in set of Fig. 20. The result revealed that the expansion could be

controlled in the applied voltage range from 0 to 500 V.

Fig. 20. Applied voltage dependence of coil expansion.

4. Nanooptics: Brilliant Blue Observation from a

Morpho-Butterfly-Scale Quasi-Structure

TheMorpho-butterfly has mysteriously brilliant blue wings, and the

source of this color has been an interesting scientific problem for a longtime. Through an intriguing optical phenomenon, the scales reflect

interfered brilliant blue color for any incidence angle of white light. This

color is called a structural color, meaning that it is not caused by pigment

reflection [15]. When we observed the scales with a scanning electron

microscope (SEM) (Fig. 21(a)), we found three-dimensional (3D)

nanostructures with 2-m height, 0.7-m width, and a 0.22 m grating

pitch on the scales. These nanostructures caused the optical phenomenonin the same way as the play of color is produced in an opal and

iridescence is produced by a jewel beetle.

We fabricated the Morpho-butterfly-scale quasi-structure with a

commercially available FIB system (SMI9200: SII Nanotechnology Inc.)

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using a Ga+

ion beam operating at 30 kV [16]. The beam diameter was

about 7 nm at 0.4 pA. The FIB-CVD was done using a precursor of

phenanthrene (C14H10).

Fig. 21.Morpho-butterfly scales. (a) Top view optical microscope image ofMorpho-

butterfly. Cross-sectional view SEM image ofMorpho-butterfly scales. (b) Inclined-view

SIM images ofMorpho-butterfly-scale quasi-structure fabricated by FIB-CVD.

In this experiment, we used a computer-controlled pattern generator,

which converted 3-D computer-aided design (CAD) data into a scanning

signal, as an FIB scanning apparatus to fabricate a 3-D mold [8]. The

scattering range of Ga primary ion is about 20 nm and secondly electron

range induced by Ga ion beam is about 20 nm, therefore the expected

pattern resolution of the FIB-CVD was about 80 nm.

Figure 21(b) is a scanning ion microscope (SIM) image of the

Morpho-butterfly quasi-structure fabricated by FIB-CVD using 3-DCAD data. This result demonstrates that FIB-CVD can be used to freely

fabricate the quasi-structure.

We measured the reflection intensity from Morpho-butterfly

scales and the Morpho-butterfly-scale quasi-structure through optical

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measurement. In this measurement system, white light from a halogen

lamp was directed onto a sample with incident angles ranging from 5 to

45. The reflection was concentrated by an optical microscope andanalyzed by a commercially available photonic multi-channel spectral

analyzer system (PMA-11: Hamamatsu Photonics K.K.). The intensity of

incident light from the halogen lamp had a wavelength with peak

intensity close to 630 nm.

The Morpho-butterfly-scale quasi-structure was made of DLC. The

reflectivity and transmittance of a 200-nm-thick DLC film deposited by

FIB-CVD, measured by the optical measurement system at a wavelengthclose to 440 nm (the reflection peak wavelength of theMorpho-butterfly),

were 30% and 60%, respectively. The measured data thus indicated that

the DLC film had high reflectivity near 440 nm, which is important for

fabrication of an accurateMorpho-butterfly-scale quasi-structure.

Fig. 22. Intensity curves of reflection spectra. (a) Morpho-butterfly scales. (b) Morpho-

butterfly-scale quasi-structure.

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We measured the reflection intensities ofMorpho-butterfly scales

and the quasi-structure with an optical measurement system, and

compared their characteristics. Figures 22(a) and 22(b) respectively showthe reflection intensity from Morpho-butterfly scales and the quasi-

structure. Both had a wavelength whose peak intensity was near 440 nm

and showed very similar reflection intensity spectra for the various

incidence angles.

We have thus successfully demonstrated that a Morpho-butterfly-

scale quasi-structure fabricated by FIB-CVD can show nearly the same

optical characteristics as realMorpho-butterfly scales.

5. Nanobiology

5.1. Nanoinjector

Three-dimensional nanostructures on a glass capillary have a number

of useful applications such as manipulators and sensors in the variousmicrostructures. We have demonstrated the fabrication of a nozzle

nanostructure on a glass capillary for a bio injector by 30 keV Ga+

focused-ion-beam assisted deposition with a precursor of phenanthrene

vapor and etching [17]. It has been demonstrated that nozzle

nanostructures with various shapes and sizes have been successfully

fabricated. An inner tip diameter of 30 nm on a glass capillary and a tip

shape with an inclined angle have been realized. We reported that

diamond-like carbon (DLC) pillars grown by FIB-CVD with a precursor

of phenanthrene vapor have very large Young modulus that exceeds

600 GPa, which gives great possibilities for various applications [10].

These characteristics are very useful for various biological device

fabrications.

In this experiment, a nozzle nanostructure fabrication for biological

nanoinjector research has been studied. The tip diameters of conventional

bio-injectors are over 100 nm and tip shapes cannot be controlled. A bio-

nanotool with various nanostructures on the top of a glass capillary has

the following feature usages shown in Fig. 23: (1) injection of various

reagents into a specific organelle in a cell, (2) selective manipulation of a

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specific organelle out side of a cell by using the nanoinjector as an

aspirator, (3) reduction of the mechanical stress when operating into the

cell by controlling the shape and the size of the bio-nanoinjector, and (4)measurment of the electric potential of a cell, an organelle, and an ion

channel exiting on a membrane by fabricating an electrode. Thus far, 3D

nanostructure fabrications on a glass capillary have not been reported.

We presents nozzle nanostructure fabrication on a glass capillary by FIB-

CVD and etching to confirm the possibility of bio-nanoinjector

fabrication.

Fig. 23. Usages of bio-nanoinjector.

The nozzle structures of the nano injector were fabricated using

a function generator (Wave Factory: NF Electronic Instruments).

Conventional microinjectors are fabricated by pulling a glass capillary

(GD-1: Narishige Co.) using a micropipette puller (PC-10: Narishige

Co.). The dimensions of the glass capillary are 90 mm in length and

1 mm in diameter.Conventionally, the tip-shape control of a microinjector made by

pulling a glass capillary, which is used as an injector into a cell, is carried

out without or with mechanical grinding. However, the reliability of tip-

shape control is very poor and depends on a personal experience.

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Fig. 24. SIM images of bio-nanoinjector fabricated on a glass capillary by FIB-CVD.

(a) before FIB-CVD, (b) after FIB-CVD, and (c) cross section of (b).

Fig. 25. Injection into an egg cell (Ciona intestinalis) using a bio-nanoinjector.

A bio-nanoinjector tip was fabricated on a glass capillary by FIB-

CVD as shown in Figs. 24(a)-24(c). First, FIB etching makes the tip

surface of the glass capillary smooth. And then, a nozzle structure was

fabricated on the tip by FIB-CVD. Figure 24(a) shows the tip surface

smoothed at 120 pA and 30 s exposure time by FIB-etching with an inner

hole diameters of 870 nm. The nozzle structure fabricated by FIB-CVD

with an inner hole diameters of 220 nm was shown in Fig. 24(b).

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Figure 24(c) corresponds to a cross section of Fig. 24(b). These results

demonstrate that a bio-nanoinjector could be successfully fabricated by a

3D nanostructure fabrication using FIB-CVD. The bio-nanoinjector wasused to inject dye into a egg cell (Ciona intestinalis) as shown in Fig. 25.

5.2. Nanomanipulator

An electrostatic 3-D nano-manipulator that can perform inclusion of

nano parts and cell operation has been developed by FIB-CVD. This 3-D

nano manipulator has four fingers in order to catch the target of variousshapes certainly. The movable principle is that an electric charge is

accumulated in the structure by applying voltage to four fingers structure

and it move by repulsion of the electric charge. Furthermore, we

succeeded to catch the micro-sphere (polystyrene latex with a diameter

of 1 m) by using this 3-D nano-manipulator with four fingers [18].

Fig. 26. SIM image of the 3D electrostatic nano-manipulator with four fingers before

manipulation.

First, pulling of a glass capillary (GD-1; NARISHIGE CO.) was

performed by using micropipette puller (PC-10; NARISHIGE CO.).

About 1.0 m diameter tip of a glass capillary could be obtained in this

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process. Second, Au coating of the glass capillary surface was carried out

in order to fabricate an electrode for nano-manipulator control. Au

thickness that carried out coating at this time was about 30 nm. Finally,3-D nano-manipulator structure with four fingers (Fig. 26) was fabricated

by FIB-CVD on the tip of the glass capillary with single electrode. A

sphere can also be caught easily and certainly by doing so. That is,

although it is expected that it is difficult to catch a sphere by a pair of

chopsticks, it will become less difficult to catch a sphere, if the

manipulator has several fingers like mans hand.

Fig. 27. Illustration of 1 m polystyrene micro-sphere manipulation by using 3-Delectrostatic nano-manipulator with four fingers.

Micro-sphere (polystyrene latex with a diameter of 1 m)

manipulation was carried out under the optical microscope by using

3-D nano-manipulator with four fingers. The illustration describing

the situation of a manipulation experiment is shown as Fig. 27. By

connecting the manipulator fabricated by FIB-CVD to a commercialmanipulator (MHW-3; NARISHIGE CO.), the movement of the direction

of an X-axis, a Y-axis, and Z-axis was controlled. And the micro-sphere

that is a target was fixed to the side of a glass capillary, and the situation

of manipulation was observed from the top with the optical microscope.

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Fig. 28. In-situ observation of 1 m polystyrene micro-sphere manipulation by using 3-D

electrostatic nano-manipulator with four fingers.

Fig. 29. SIM image of the 3-D electrostatic nano-manipulator with four fingers after

manipulation.

And, optical microscope image of Fig. 28 shows the situation duringmanipulation. First, the 3-D nano-manipulator was made to approach a

micro-sphere without applying voltage. Next, four fingers were opened by

applying 600V before the micro-sphere and the micro-sphere was caught

by turning off voltage in the position which can catch the micro-sphere.

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And then, the 3-D nano-manipulator was taken off from the side of a

glass capillary. At this time, voltage is not applied to the manipulator and

the force of catching the micro-sphere is the elastic force of amanipulators own structure. We succeeded to catch the micro-sphere as

shown in SIM image of Fig. 29.

6. Summary

Three-dimensional nanostructure fabrication has been demonstrated

by 30 keV Ga+

FIB-CVD using a phenanthrene (C14H10) source as a

precursor. The characterization of deposited film on a silicon substrate

was performed by a transmission microscope and Raman spectra. This

result indicates that the deposition film is a diamondlike amorphous

carbon (DLC) which have attractive attention because of their hardness,

chemical inertness and optical transparency. A large Youngs modulus

that exceeds 600 GPa seems to present great possibilities for various

applications. Nanoelectrostatic actuator, and nano-space-wiring with

0.1 m dimension were fabricated and evaluated as parts of

nanomechanical system. Furthermore, nanoinjector and nanomanipulator

were fabricated as a novel nano-tool for manipulation and analysis of

subcellular organelles. These results demonstrate that FIB-CVD is one of

key technologies to make 3D nanostructure devices in the field of

electronics, mechanics, optics and biology.

References

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Sci. Technol. B8, 1557 (1990)., P.G. Blauner, Proc. 1991 Int. MicroProcess Conf.

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8. T. Hoshino, K. Watanabe, R. Kometani, T. Morita, K. Kanda, Y. Haruyama,T. Kaito, J. Fujita, M. Ishida, Y. Ochiai and S. Matsui, J. Vac. Sci. & Technol. B21,

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15. P. Vukusic and J. Roy. Sambles, Nature 424, 852 (2003).16. K. Watanabe, T. Hoshino, K. Kanda, Y. Haruyama, and S. Matsui, Jpn. J. Appl.

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