**3.3 Application of self-ordered nanoparticle films on substrate**

The possibility of developing new functional materials with nanoparticle films has been pointed out for a long time [46], and many attempts have been made mainly to create light-emitting devices using the visible light emission from silicon

nanoparticles [47–51]. Chen et al. [52] accumulated silicon nanoparticles on a substrate in an argon and oxygen atmosphere and researched on the effects of the gas pressure and annealing way on photoluminescence (PL). As a result, it was concluded that the emission band of 1.8–2.1 eV obtained from the experiments is based on the quantum effect since the blueshift of the emission varies depending on the nanoparticle size. Also, by accumulating silicon nanoparticles on a substrate in helium gas atmosphere, Kabashin et al. [53] found out that the microstructure on the nanoparticle film's surface varied depending on the helium gas pressure. When the helium gas pressure is higher than 1.5 Torr, it becomes a shape of porous film. Furthermore, it is concluded that the morphology of microstructure on the film surface determines the extent to which the natural oxidation of silicon nanoparticle affects PL luminescence.

In addition, the nanoparticle properties of iron oxide [54] and cobalt oxide [55] are studied for applying to a new functional device and material such as magnetic recording media, magnetic fluids and gas sensors. The properties of tungsten oxide nanoparticles [56] have been under research for being used as photocatalysts. However, while these applications of nanoparticles are still in the experimental stage, monodispersed nanoparticle beams are expected to improve the accuracy of these experiments.

On the other hand, from before, some studies focused attention on the function of laser irradiation to create an ordering of nanoparticles and investigated the influences of the intense and direction of electric field on the ordering appearance of nanoparticles. The phenomenon was called by Laser-Induced Periodic Surface Structures (LIPSS) [57, 58], which have led to a growing interest on how to build a new order of the nanoparticle array, as represented by the image of **Figure 7**. And Han et al. [59] confirmed by experiments and simulations that low-energy nanoparticle beams are effective in producing films of small nanoparticles with a wide range of sizes. Moreover, since the formation of ordered array is essential for making larger films, the technology of forming ordered nanoparticles by irradiating the substrate's surface with the beam of monodispersed nanoparticles which have a stable crystal structure has been expected. It is verified that the silicon nanoparticles fabricated by this technology spontaneously form a nanostructure ordering, and the formation

#### **Figure 7.**

*SEM image of silicon nanoparticles produced by PLD and their long-range ordering controlled by subsequent laser irradiation [57].*

**113**

*Nanoparticle Formation and Deposition by Pulsed Laser Ablation*

mechanism has been studied [60]. The components of this structure are called silicon nanoblocks [61], which are expected to be applied on next-generation devices such as accumulator integration system with a solar cell [62], ultra-thin supercapacitor [63] and superlattice structures [45]. The silicon clusters possesing atomic crystalline structures generated by SCCS are depositing on the graphene substrate

*HRTEM image of silicon cluster superlattice structures obtained with the use of the new laser ablation-type* 

In addition, it is found that interparticle spacing and pattern are the important parameters for characterizing the film consisting of nanoparticle array. We can extract the useful properties from the nanoparticle films, depending on the interparticle spacing range of electron tunneling, optical near field or spin exchange interaction. In the next generation of laser ablation, it seems to be one of critical challenges to clarify and control the ordering of nanoparticles based on the view-

To apply the nanostructured particle films on new functional materials, it is important to study the formation process. Therefore, in this chapter, we stared from the mechanism of laser ablation process and then found that monodispersed nanoparticle beams are necessary for fabricating nanoparticle films and that, when used as a macroscopic material, the technology based on the self-ordering of nanoparticles is essential to make large films. It is expected to control the interparticle spacing and its pattern of nanoparticle structure in the films to obtain new and useful properties which are potentially underlying in the films as functional devices. In order to realize such devices, laser ablation remains a promising technol-

and forming shapes of silicon superlattice as shown in **Figure 8**.

ogy for the future, and worth studied for more possibilities.

point of the interparticle spacing.

**4. Summary**

**Figure 8.**

*silicon cluster beam system [45].*

*DOI: http://dx.doi.org/10.5772/intechopen.95299*

*Nanoparticle Formation and Deposition by Pulsed Laser Ablation DOI: http://dx.doi.org/10.5772/intechopen.95299*

#### **Figure 8.**

*Practical Applications of Laser Ablation*

affects PL luminescence.

these experiments.

nanoparticles [47–51]. Chen et al. [52] accumulated silicon nanoparticles on a substrate in an argon and oxygen atmosphere and researched on the effects of the gas pressure and annealing way on photoluminescence (PL). As a result, it was concluded that the emission band of 1.8–2.1 eV obtained from the experiments is based on the quantum effect since the blueshift of the emission varies depending on the nanoparticle size. Also, by accumulating silicon nanoparticles on a substrate in helium gas atmosphere, Kabashin et al. [53] found out that the microstructure on the nanoparticle film's surface varied depending on the helium gas pressure. When the helium gas pressure is higher than 1.5 Torr, it becomes a shape of porous film. Furthermore, it is concluded that the morphology of microstructure on the film surface determines the extent to which the natural oxidation of silicon nanoparticle

In addition, the nanoparticle properties of iron oxide [54] and cobalt oxide [55] are studied for applying to a new functional device and material such as magnetic recording media, magnetic fluids and gas sensors. The properties of tungsten oxide nanoparticles [56] have been under research for being used as photocatalysts. However, while these applications of nanoparticles are still in the experimental stage, monodispersed nanoparticle beams are expected to improve the accuracy of

On the other hand, from before, some studies focused attention on the function of laser irradiation to create an ordering of nanoparticles and investigated the influences of the intense and direction of electric field on the ordering appearance of nanoparticles. The phenomenon was called by Laser-Induced Periodic Surface Structures (LIPSS) [57, 58], which have led to a growing interest on how to build a new order of the nanoparticle array, as represented by the image of **Figure 7**. And Han et al. [59] confirmed by experiments and simulations that low-energy nanoparticle beams are effective in producing films of small nanoparticles with a wide range of sizes. Moreover, since the formation of ordered array is essential for making larger films, the technology of forming ordered nanoparticles by irradiating the substrate's surface with the beam of monodispersed nanoparticles which have a stable crystal structure has been expected. It is verified that the silicon nanoparticles fabricated by this technology spontaneously form a nanostructure ordering, and the formation

*SEM image of silicon nanoparticles produced by PLD and their long-range ordering controlled by subsequent* 

**112**

**Figure 7.**

*laser irradiation [57].*

*HRTEM image of silicon cluster superlattice structures obtained with the use of the new laser ablation-type silicon cluster beam system [45].*

mechanism has been studied [60]. The components of this structure are called silicon nanoblocks [61], which are expected to be applied on next-generation devices such as accumulator integration system with a solar cell [62], ultra-thin supercapacitor [63] and superlattice structures [45]. The silicon clusters possesing atomic crystalline structures generated by SCCS are depositing on the graphene substrate and forming shapes of silicon superlattice as shown in **Figure 8**.

In addition, it is found that interparticle spacing and pattern are the important parameters for characterizing the film consisting of nanoparticle array. We can extract the useful properties from the nanoparticle films, depending on the interparticle spacing range of electron tunneling, optical near field or spin exchange interaction. In the next generation of laser ablation, it seems to be one of critical challenges to clarify and control the ordering of nanoparticles based on the viewpoint of the interparticle spacing.

### **4. Summary**

To apply the nanostructured particle films on new functional materials, it is important to study the formation process. Therefore, in this chapter, we stared from the mechanism of laser ablation process and then found that monodispersed nanoparticle beams are necessary for fabricating nanoparticle films and that, when used as a macroscopic material, the technology based on the self-ordering of nanoparticles is essential to make large films. It is expected to control the interparticle spacing and its pattern of nanoparticle structure in the films to obtain new and useful properties which are potentially underlying in the films as functional devices. In order to realize such devices, laser ablation remains a promising technology for the future, and worth studied for more possibilities.

*Practical Applications of Laser Ablation*
