**2.3 The welding and the carbon nanowire network fabrication**

The fabrication of components on nanoscale is required for the construction of modern electronic and optical electronic nanodevices. The nanoscale interconnections are also required between building blocks and in interior of building blocks in order to obtain further miniaturized nanoscale devices. CNTs or metallic or semiconductor nanowire can be used as interconnection in electronic devices. Until now, various nanometer-scale optical electronic and electronic devices have been constructed successfully via uncomplicated interconnections, but still a lot of difficulties are arising in constructing complicated devices. Major technical obstacle is

**61**

interconnections.

carbon atoms and vacancies.

*Reaction between Energy Particle Ion Beam with Carbon Nanotube*

the production of a variety of junctions and complicated networks for interconnections of building blocks. A variety of multiple-way junctions and networks of nanotubes and junctions in different shapes of amorphous carbon nanowires have been manufactured successfully by arc discharge method and chemical vapor deposition (CVD) method [24–28]. The center of the junctions prepared by these methods is the location of the metal catalyst. Hydrocarbon-reactive groups are continuously subjected to a process of melting precipitation on the surface of the catalyst and can form these junctions under specific experimental conditions. Therefore, the eradication of metal catalyst nanoparticles may destroy carbon nanotube networks. Furthermore, the effect of the interaction between the nanoparticles with the nanotubes on the properties of devices is not under consideration. Comparing with the arc discharge and CVD, the interconnections of CNTs or carbon nanowires fabricated by ion beam irradiation are by means of the formation of C–C bonds on the surface through the structural reorganization around the defect induced by ions. The various multiple-way junctions and networks of nanotubes or nanowires by ion beam irradiation are interaction of itself, not by means of the metal crystal nanoparticle, which is very important for the development of the miniaturization

In our previous work [16, 29, 30], the interaction of CNTs and the kilo-electronvolt ion beam has been investigation. The amorphous carbon nanowire network has been fabricated, and the welding of CNTs can also be achieved. **Figure 7** displays the typical SEM and TEM images of CNTs being irradiated by a beam of Si ions. Networks of amorphous carbon nanowires are formed after being irradiated by Si ions. Alterations in the structures of CNTs are found to be initiated after exposure to energetic Si ions which might be due to collision cascade effect that leads to ejection of carbon atoms, and the structure of CNTs is transformed into solid amorphous carbon nanowires at higher beam fluencies. Diameters of amorphous carbon

The junctions of amorphous carbon nanowire have Y and X type. The amorphous carbon nanowires can form the network by the connection effect of junction. The inset image shows that the thickness of the amorphous carbon nanowire network layer is 0.6 μm and the amorphous carbon nanowire network layer can be detached from CNTs by introducing empty space below it. An empty space between amorphous carbon nanowire networks and CNTs was set up by reducing the space between amorphous carbon nanowires beside the route of ion beam owing to their

**Figure 8** demonstrates the procedure for fabrication of amorphous carbon nanowire networks in three steps which are based on experimental observation. At first, the atomic network of nanotubes is formed by steady process of amorphization introduced by ion beam irradiation. The energy of an ion is shifted to atoms of the uppermost shell of MWCNTs and leads to produce recoils of several primary

Recoils of energetic carbon atoms will then generate more recoil upon collision with carbon atoms of other shells because of collision cascade effect and hence will add on to the process of damage creation collectively with the ion which further leads to the formation of an amorphous region. When the two nanotubes in overlapping positions are being irradiated by certain fluencies of ion beams, the bond will be formed due to reforming near the irradiation-induced vacancies which may be served as conduit between nanowires and lead to fuse and connect carbon nanowires in form of networks. The carbon atoms in nanotubes are lighter than silicon ions; therefore, a lot of forward carbon recoils will be produced due to collision between the silicon ion and the carbon atoms. In this way, more carbon atoms should be shifted to carbon nanotube films on its inner side where it is distributed loosely.

*DOI: http://dx.doi.org/10.5772/intechopen.85529*

of electronic and optical electronic devices.

nanowires are uniform, and surfaces are smooth laterally.

**Figure 6.** *SEM images of CNTs irradiated by 1.2 keV Ar ions for 15–60 min [23].*

### *Reaction between Energy Particle Ion Beam with Carbon Nanotube DOI: http://dx.doi.org/10.5772/intechopen.85529*

*Ion Beam Techniques and Applications*

sputtering CNTs is speculated.

bers by Ar+

After 45 min sputtering, the all-tube morphology of CNTs on the top layer of CNTs stacks is broken, and the tube morphology of CNTs at the bottom of CNTs stacks is almost intact; some protrusions can be observed on the coarse aggregated nanoparticle surface. With 60-min sputtering, all CNTs are broken, and some nanofibers can be observed; the lengths of nanofibers are ranged from several ten nanometers to several micrometers. The high-resolution SEM images of typical nanofiber show that the nanofibers grow on the tip of protrusion. The formation of carbon nanofi-

Initially, structures of CNTs are modified due to the presence of large number of defects, i.e., vacancies and interstitials between and on tube walls due to collision cascade effect that gives rise to degree of disorder in the structure, and consequently, CNTs might be scrunched up in form of amorphous nanowires.

Carbon atoms are sputtered quickly on some regions because of difference in sputtering yields which depends on curvature of the amorphous nanowire surface and lead to break CNTs, and some particles will be deposited along the axis of tubes. Afterward, flanges are formed due to competition between smoothening process and roughening process. At last, the migration of mass redeposition atom

The fabrication of components on nanoscale is required for the construction of modern electronic and optical electronic nanodevices. The nanoscale interconnections are also required between building blocks and in interior of building blocks in order to obtain further miniaturized nanoscale devices. CNTs or metallic or semiconductor nanowire can be used as interconnection in electronic devices. Until now, various nanometer-scale optical electronic and electronic devices have been constructed successfully via uncomplicated interconnections, but still a lot of difficulties are arising in constructing complicated devices. Major technical obstacle is

toward the tip leads to the growth of carbon nanofibers on the protrusion.

**2.3 The welding and the carbon nanowire network fabrication**

**60**

**Figure 6.**

*SEM images of CNTs irradiated by 1.2 keV Ar ions for 15–60 min [23].*

the production of a variety of junctions and complicated networks for interconnections of building blocks. A variety of multiple-way junctions and networks of nanotubes and junctions in different shapes of amorphous carbon nanowires have been manufactured successfully by arc discharge method and chemical vapor deposition (CVD) method [24–28]. The center of the junctions prepared by these methods is the location of the metal catalyst. Hydrocarbon-reactive groups are continuously subjected to a process of melting precipitation on the surface of the catalyst and can form these junctions under specific experimental conditions. Therefore, the eradication of metal catalyst nanoparticles may destroy carbon nanotube networks. Furthermore, the effect of the interaction between the nanoparticles with the nanotubes on the properties of devices is not under consideration. Comparing with the arc discharge and CVD, the interconnections of CNTs or carbon nanowires fabricated by ion beam irradiation are by means of the formation of C–C bonds on the surface through the structural reorganization around the defect induced by ions. The various multiple-way junctions and networks of nanotubes or nanowires by ion beam irradiation are interaction of itself, not by means of the metal crystal nanoparticle, which is very important for the development of the miniaturization of electronic and optical electronic devices.

In our previous work [16, 29, 30], the interaction of CNTs and the kilo-electronvolt ion beam has been investigation. The amorphous carbon nanowire network has been fabricated, and the welding of CNTs can also be achieved. **Figure 7** displays the typical SEM and TEM images of CNTs being irradiated by a beam of Si ions. Networks of amorphous carbon nanowires are formed after being irradiated by Si ions. Alterations in the structures of CNTs are found to be initiated after exposure to energetic Si ions which might be due to collision cascade effect that leads to ejection of carbon atoms, and the structure of CNTs is transformed into solid amorphous carbon nanowires at higher beam fluencies. Diameters of amorphous carbon nanowires are uniform, and surfaces are smooth laterally.

The junctions of amorphous carbon nanowire have Y and X type. The amorphous carbon nanowires can form the network by the connection effect of junction. The inset image shows that the thickness of the amorphous carbon nanowire network layer is 0.6 μm and the amorphous carbon nanowire network layer can be detached from CNTs by introducing empty space below it. An empty space between amorphous carbon nanowire networks and CNTs was set up by reducing the space between amorphous carbon nanowires beside the route of ion beam owing to their interconnections.

**Figure 8** demonstrates the procedure for fabrication of amorphous carbon nanowire networks in three steps which are based on experimental observation. At first, the atomic network of nanotubes is formed by steady process of amorphization introduced by ion beam irradiation. The energy of an ion is shifted to atoms of the uppermost shell of MWCNTs and leads to produce recoils of several primary carbon atoms and vacancies.

Recoils of energetic carbon atoms will then generate more recoil upon collision with carbon atoms of other shells because of collision cascade effect and hence will add on to the process of damage creation collectively with the ion which further leads to the formation of an amorphous region. When the two nanotubes in overlapping positions are being irradiated by certain fluencies of ion beams, the bond will be formed due to reforming near the irradiation-induced vacancies which may be served as conduit between nanowires and lead to fuse and connect carbon nanowires in form of networks. The carbon atoms in nanotubes are lighter than silicon ions; therefore, a lot of forward carbon recoils will be produced due to collision between the silicon ion and the carbon atoms. In this way, more carbon atoms should be shifted to carbon nanotube films on its inner side where it is distributed loosely.

**Figure 7.** *Images of CNTs (TEM and SEM) irradiated by 40 keV Si ions [29].*

*The process of amorphous carbon nanowire network formation [29].*

These carbon recoils will make a bond with vacancies on the surface of CNTs or amorphous carbon nanowires that leads to join or interconnect adjacent overlapped CNTs or amorphous carbon nanowires.

**63**

**Figure 9.**

*Reaction between Energy Particle Ion Beam with Carbon Nanotube*

Under the influence of channel effect, a beam of Si ions pushes nanowires or nanotubes near to the ion source to the dense region of carbon material. Due to this process, stacks of carbon nanotubes will become dense, and space will decrease which will be beneficial to fuse the nanotubes. On the other hand, amorphous carbon nanowire networks will unlock the deepest layer of carbon nanotubes which is unapproachable by the beam of ions because of fusion or coalescence of nanowireinduced strains; hence, an empty space is left behind just below the networks of

Eventually, with the increase in fluence of ions to be implanted, a large amount of junctions will be produced that leads to connect the adjacent amorphous carbon nanowires and form the network. With further increase in fluence of ions, sputtering will occur in the thick amorphous carbon nanowire networks, and sputter-induced carbon atoms will be deposited on the surface of network; hence,

Carbon, nitrogen lighter ions, silicon, and argon heavier ions with the same incident energy also have been used to interact with CNTs in order to achieve carbon nanowire network [16]. The morphology change of CNTs shows similar tangency under the irradiation of ion beam of different species with the energy of 40 keV. Carbon nanowire network fabrication occurred in the following steps: (a) local amorphization of nanotubes, (b) fabrication of some simple junctions, and (c) formation of networks. The irradiation fluencies are differing for forming the nanowire networks of

The threshold beam fluence of C, N, Si, and Ar ion for the formation of carbon

And the corresponding SEM images of carbon nanowire network by the irradiation of C, N, Si, and Ar ion with the threshold dose are shown in **Figure 9**. The carbon nanowire network can be fabricated by the irradiation of different ion beams. Therefore, it is concluded that the formation of carbon nanowire networks induced

*SEM images of carbon nanowire networks by the irradiation of C, N, Si, and Ar ion with the threshold dose [16].*

, respectively.

nanowire networks is 1 × 1017, 1 × 1017, 5 × 1016, and 5 × 1016 ions/cm2

*DOI: http://dx.doi.org/10.5772/intechopen.85529*

amorphous carbon nanowire.

continuous film will be formed.

carbon and having different species of ions.

by ion beam irradiation is a universal technique.

### *Reaction between Energy Particle Ion Beam with Carbon Nanotube DOI: http://dx.doi.org/10.5772/intechopen.85529*

*Ion Beam Techniques and Applications*

**62**

**Figure 8.**

**Figure 7.**

CNTs or amorphous carbon nanowires.

*The process of amorphous carbon nanowire network formation [29].*

*Images of CNTs (TEM and SEM) irradiated by 40 keV Si ions [29].*

These carbon recoils will make a bond with vacancies on the surface of CNTs or amorphous carbon nanowires that leads to join or interconnect adjacent overlapped

Under the influence of channel effect, a beam of Si ions pushes nanowires or nanotubes near to the ion source to the dense region of carbon material. Due to this process, stacks of carbon nanotubes will become dense, and space will decrease which will be beneficial to fuse the nanotubes. On the other hand, amorphous carbon nanowire networks will unlock the deepest layer of carbon nanotubes which is unapproachable by the beam of ions because of fusion or coalescence of nanowireinduced strains; hence, an empty space is left behind just below the networks of amorphous carbon nanowire.

Eventually, with the increase in fluence of ions to be implanted, a large amount of junctions will be produced that leads to connect the adjacent amorphous carbon nanowires and form the network. With further increase in fluence of ions, sputtering will occur in the thick amorphous carbon nanowire networks, and sputter-induced carbon atoms will be deposited on the surface of network; hence, continuous film will be formed.

Carbon, nitrogen lighter ions, silicon, and argon heavier ions with the same incident energy also have been used to interact with CNTs in order to achieve carbon nanowire network [16]. The morphology change of CNTs shows similar tangency under the irradiation of ion beam of different species with the energy of 40 keV. Carbon nanowire network fabrication occurred in the following steps: (a) local amorphization of nanotubes, (b) fabrication of some simple junctions, and (c) formation of networks.

The irradiation fluencies are differing for forming the nanowire networks of carbon and having different species of ions.

The threshold beam fluence of C, N, Si, and Ar ion for the formation of carbon nanowire networks is 1 × 1017, 1 × 1017, 5 × 1016, and 5 × 1016 ions/cm2 , respectively. And the corresponding SEM images of carbon nanowire network by the irradiation of C, N, Si, and Ar ion with the threshold dose are shown in **Figure 9**. The carbon nanowire network can be fabricated by the irradiation of different ion beams. Therefore, it is concluded that the formation of carbon nanowire networks induced by ion beam irradiation is a universal technique.

So far, CNTs are transformed into amorphous carbon nanowire networks after exposure to radiations and not the CNT networks.

The theoretical simulation demonstrated that CNT junctions might perhaps be fabricated only when CNTs are irradiated under the heating conditions [31]. Therefore, the substrate was heated during the irradiation of ion beams in order to achieve multi-walled CNT (MWCNT) junctions [30]. TEM and HRTEM images of MWCNTs after exposure to a beam of Si ions at temperatures ~550 and ~600 K are represented in **Figure 10**.

At T~550 K, irradiated MWCNTs and formed MWCNT junctions are found to have hollow structure, and the carbon nanowires are amorphous carbon structures, but few graphitic layer structures still exist in MWCNTs and formed junctions.

The existence of well-ordered graphitic layer structures is apparent in the irradiated MWCNTs and formed MWCNT junctions, but there is no evidence of existence of hollow structure at T = ~600 K.

The investigations indicate that the temperature is the main factor in fabrication of well-ordered graphite structure of CNT junctions. The heating temperature is the key factor that improves the rate of defect recombination and easily forms the well-ordered graphite structure, not the amorphous carbon nanowires. **Figure 10** shows the structure of formed MWCNT junctions in detail.

Common graphitic sheets are shared adjacent parts of two MWCNTs and form the MWCNT junction. Moreover, the sum of the thicknesses of the wall "A"

**Figure 10.** *TEM and HRTEM images of MWCNTs being irradiated by Si ions at temperatures ~550 and ~600 K [30].*

**65**

**Figure 11.**

*Reaction between Energy Particle Ion Beam with Carbon Nanotube*

structure of amorphous carbon to ordered structure of carbon.

(5.5 ± 0.1 nm) and wall "B" (4.5 ± 0.1 nm) is less as compared to the thickness of the junction (11.0 ± 0.1 nm) in the conjoint area of the both MWCNTs as shown in the lines I, II, and III. It is indicated that exposure of MWCNT to radiations at high temperature will form junctions due to self-assembling of sputtered carbon atoms and initiate the process of alteration of disordered graphite lattice to the ordered lattice on outer walls of MWCNTs. Si ion beam irradiation-induced structural transformations in MWCNTs system will make interconnection between MWCNTs, and this process is the same as electron beam irradiation-induced transformations of

It is observed from experimental results that joining of MWCNTs with well-

600–850 K. Except for the effect of heating temperature, the ion dose should affect the welding of CNTs; TEM images of MWCNTs irradiated by Si ion beam with different doses at temperature ~600 K are shown in **Figure 11**. There are no junctions

irradiated MWCNTs and the formed junctions only have amorphous structure. At low beam fluence, disordered graphite lattices and sputtered carbon atoms might not be sufficient to connect two nearby MWCNTs, and structure of MWCNTs might be spoiled to that extent which would not be cured at high temperature of high radiation dose. Based on the investigation of the experiment,

*TEM images of MWCNTs irradiated by beam of Si ions with different doses at temperature ~600 K [30].*

. The hollow structure of MWCNTs has vanished

, and related HRTEM image shows that both the

ordered graphitic layer structures is possible at temperature in the range

*DOI: http://dx.doi.org/10.5772/intechopen.85529*

at the dose of 1 × 1016 ions/cm2

with the dose of 5 × 1017 ions/cm2

### *Reaction between Energy Particle Ion Beam with Carbon Nanotube DOI: http://dx.doi.org/10.5772/intechopen.85529*

*Ion Beam Techniques and Applications*

represented in **Figure 10**.

exposure to radiations and not the CNT networks.

existence of hollow structure at T = ~600 K.

shows the structure of formed MWCNT junctions in detail.

So far, CNTs are transformed into amorphous carbon nanowire networks after

The theoretical simulation demonstrated that CNT junctions might perhaps be fabricated only when CNTs are irradiated under the heating conditions [31]. Therefore, the substrate was heated during the irradiation of ion beams in order to achieve multi-walled CNT (MWCNT) junctions [30]. TEM and HRTEM images of MWCNTs after exposure to a beam of Si ions at temperatures ~550 and ~600 K are

At T~550 K, irradiated MWCNTs and formed MWCNT junctions are found to have hollow structure, and the carbon nanowires are amorphous carbon structures, but few graphitic layer structures still exist in MWCNTs and formed junctions. The existence of well-ordered graphitic layer structures is apparent in the irradiated MWCNTs and formed MWCNT junctions, but there is no evidence of

The investigations indicate that the temperature is the main factor in fabrication of well-ordered graphite structure of CNT junctions. The heating temperature is the key factor that improves the rate of defect recombination and easily forms the well-ordered graphite structure, not the amorphous carbon nanowires. **Figure 10**

Common graphitic sheets are shared adjacent parts of two MWCNTs and form the MWCNT junction. Moreover, the sum of the thicknesses of the wall "A"

*TEM and HRTEM images of MWCNTs being irradiated by Si ions at temperatures ~550 and ~600 K [30].*

**64**

**Figure 10.**

(5.5 ± 0.1 nm) and wall "B" (4.5 ± 0.1 nm) is less as compared to the thickness of the junction (11.0 ± 0.1 nm) in the conjoint area of the both MWCNTs as shown in the lines I, II, and III. It is indicated that exposure of MWCNT to radiations at high temperature will form junctions due to self-assembling of sputtered carbon atoms and initiate the process of alteration of disordered graphite lattice to the ordered lattice on outer walls of MWCNTs. Si ion beam irradiation-induced structural transformations in MWCNTs system will make interconnection between MWCNTs, and this process is the same as electron beam irradiation-induced transformations of structure of amorphous carbon to ordered structure of carbon.

It is observed from experimental results that joining of MWCNTs with wellordered graphitic layer structures is possible at temperature in the range 600–850 K. Except for the effect of heating temperature, the ion dose should affect the welding of CNTs; TEM images of MWCNTs irradiated by Si ion beam with different doses at temperature ~600 K are shown in **Figure 11**. There are no junctions at the dose of 1 × 1016 ions/cm2 . The hollow structure of MWCNTs has vanished with the dose of 5 × 1017 ions/cm2 , and related HRTEM image shows that both the irradiated MWCNTs and the formed junctions only have amorphous structure.

At low beam fluence, disordered graphite lattices and sputtered carbon atoms might not be sufficient to connect two nearby MWCNTs, and structure of MWCNTs might be spoiled to that extent which would not be cured at high temperature of high radiation dose. Based on the investigation of the experiment,

**Figure 11.** *TEM images of MWCNTs irradiated by beam of Si ions with different doses at temperature ~600 K [30].*

it is stated combination of ion beam irradiation and heating technology can be employed as technique to construct junctions of MWCNTs.
