Ion Irradiation Technique Research Articles

Controllable fabrication and characterization of conical nanocarbon structures on polymer substrate for transparent and flexible field emission displays

AbstractThe direct fabrication of fully transparent conical nanocarbon structures (CNCSs) of controlled nanoscopic dimension on a flexible nafion substrate was achieved, using field electron source, by a novel room temperature ion irradiation technique. By controlling the sizes (below the wavelength of visible light) of the CNCSs, the transparency of the substrate can be tailored satisfactorily. The transparency of the CNCSs was observed to be around 90% in the visible regime depending on the ion irradiation time. Our results suggest that the direct fabrication of well controlled fully transparent CNCSs on any transparent and flexible substrate at room temperature could open a novel route for potential applications in future highly transparent, flexible (bendable), low weight and portable field emission displays (FEDs). (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Fabrication and Morphological Control of Ion-Induced Zinc Nanostructures

An efficient method for the fabrication of zinc (Zn) nanostructures (nanoneedles and nanofibers) of controllable density and morphology without any catalyst, hazardous chemicals or external heat supply has been investigated. By varying the ion irradiation time and the ion current density, morphological control and the density of Zn nanostructures were successfully achieved using a fast and viable ion irradiation technique. Scanning (SEM) and transmission electron microscopy (TEM) results revealed that the sputtered surface was almost entirely covered with densely distributed conical and needle-like protrusions with linear shaped (sometimes curved) nanostructures (such as nanoneedles and nanofibers) with diameters and lengths of about 20-50 nm and several hundred nanometers, respectively. Detailed analysis of selected area electron diffraction (SAED) patterns with TEM analysis indicates that the Zn nanofibers were polycrystalline in nature. A possible mechanism of the formation of Zn nanostructures is briefly discussed. These aligned arrays of Zn nanoneedles/nanofibers could be a promising material for the fabrication of zinc oxide nanostructures by subsequent oxidation of Zn nanostructures and their future application in nanodevices. Thus, it is believed that this ion irradiation technique could open up a new approach for the fabrication of many kinds of nanomaterials of controllable density.

Surface nanostructuring ofTiO2thin films by high energy ion irradiation

The effects of a high ion dose irradiation on ${\text{TiO}}_{2}$ thin films under different conditions of temperature and ion nature are discussed. We have shown that anatase ${\text{TiO}}_{2}$ thin films irradiated with ${\text{N}}^{+}$ ions at room temperature develop a typical microstructure with mounds and voids open to the surface whereas irradiations at 700 K generate a surface pattern of well-ordered nanorods aligned with the ion beam. The formation of these patterns is caused by the simultaneous effect of ion irradiation near the film surface and a film temperature favoring the structural mobilization of the defective network of the material. To explain these phenomena, a qualitative model has been proposed and further tested by irradiating the ${\text{TiO}}_{2}$ thin films with ${\text{F}}^{+}$ and ${\text{S}}^{+}$ ions under different conditions. The obtained results demonstrate that ion irradiation techniques enable the formation of tilted nanorod surface patterns with lengths of about 100 nm on anatase ${\text{TiO}}_{2}$ thin films.

Superior Radiation Resistance of ODS Ferritic Steels

The oxide dispersion strengthened (ODS) ferritic steel and non-ODS reduced-activation ferritic (RAF) steel were irradiated at 773 K by means of a dual-beam ion irradiation technique to a dose of 0.4 dpa with simultaneous helium implantation up to 1000 appm. Microstructural changes were investigated by transmission electron microscopy. The RAF steel showed a preferential formation of cavities at grain boundaries, precipitate interfaces and dislocations. In contrast, the ODS ferritic steel showed a homogeneous and fine distribution of cavities in the matrix. This paper discusses the superior resistance of the ODS ferritic steel against development of cavities in terms of the effects of nano-oxide particles dispersed in the matrix.

Characterization of the surface layer due to oxygen for the hydrogen related C–SiC films

The films containing C and about 80%SiC were deposited by R F. magnetron sputtering followed with argon ion beam bombardment to enhance the adhere strength of the substrate and then were introduced hydrogen by using hydrogen ion irradiation or high pressure permeation techniques. XPS was used to investigate the sub-surface of these C–SiC films. The results show that, apart from carbon adsorbing hydrogen, carbon–hydrogen, SiC and Si 1− x C x , contamination by oxygen reacting with Si and C in the films was apparent. Further reaction with hydrogen to form C y –Si–O–H on the sub-surface of the C–SiC films was also shown. Calculation of the concentrations of the different configurations based on Ghosh model shows that different x values in Si 1− x C x and different y values in C y –Si–O–H can be obtained due to different hydrogen introduction methods.

Transparent and Flexible Field Electron Emitters Based on the Conical Nanocarbon Structures

The fabrication of conical nanocarbon structures (CNCSs) on a transparent and flexible nafion substrate at room temperature using an ion irradiation technique and their application toward field emission displays (FEDs) have been demonstrated. The main advantage of this technique is that CNCSs can be fabricated directly on the transparent substrate while retaining the transparency of the substrate. A scanning electron microscopy (SEM) image revealed that the sputtered surface was entirely covered with CNCSs with a calculated numerical density of 6 x 10(6) /mm(2). Such nafion based CNCSs have proved to be an effective electron emitter with turn-on and threshold fields of 6.1 and 9.5 V/mum, respectively. The field enhancement factor was estimated to be 1020 from the Fowler-Nordheim (F-N) plot. Thus the room temperature fabricated CNCSs based on transparent and flexible nafion substrate would be very promising for future flexible (roll-up) and transparent FEDs.

Recent Progress of Ion Irradiation Bit Patterned Media

Recent progress of the bit patterned media fabricated by ion irradiation method is reviewed. High energy ion irradiation is a useful method to modify the magnetic properties and this technique can be used to fabricate high density bit patterned media which is a promising candidate to overcome the limit of the areal density of the conventional recording media. In order to achieve magnetic patterned structure having the feature size less than 50 nm by the ion irradiation technique, the materials whose magnetic order is easily suppressed by low dose ion irradiation are necessary. One of the candidate is L12 phase CrPt3, and the control of the magnetic order of CrPt3 by the ion irradiation and the fabrication of CrPt3 bit patterned medium are discussed.

Study of optical band gap and carbon cluster sizes formed in 100 MeV Si8+ and 145 MeV Ne6+ ions irradiated polypropylene polymer

A wide variety of material modifications in polymers have been studied by using ion irradiation techniques. Extensive research has focused on to Swift Heavy Ions (MeV’s energy), probably because of good controllability and the large penetration length in polymers. High energy ion irradiation tends to damage polymers significantly by electronic excitation and ionization. It may result into the creation of latent tracks and can also cause formation of radicals such as ablation, sputtering, chain scission and intermolecular cross-linking, creation of triple bonds and unsaturated bonds and loss volatile fragments. Polypropylene polymer films of thickness 50 μm were irradiated to the fluences of 1 × 1010, 3 × 1010, 1 × 1011, 3 × 1011, 6 × 1011 and 1 × 1012 ions/cm2 with Si8+ ions of 100 MeV energy from Pelletron accelerator at Inter University Accelerator Centre (IUAC), New Delhi and Ne6+ ions of 145 MeV to the fluences of 108, 1010, 1011, 1012 and 1013 ions/cm3 from Variable Energy Cyclotron Centre, Kolkata. Optical modifications were characterized by UV towards the red end of the spectrum with the increase of the fluence. Value of optical band gap Eg shows a decreasing trend with ion fluence irradiated with both kinds of ions. Cluster size N, the number of carbon atoms per conjugation length increases with increasing ion dose. Cluster size also increases with the increase of electronic stopping power.

Formation of single electron transistors in single-walled carbon nanotubes with low energy Ar ion irradiation technique

The single electron transistor (SET) fabrication process on the individual single-walled carbon nanotubes (SWCNTs) using low energy Ar ion irradiation technique has been demonstrated. The individual SWCNT was partly irradiated through the protection resist with the two opening windows, whose width was 50 nm, fabricated by electron beam lithography. The irradiated segments had higher resistance and worked as barriers. The SWCNT-SET successfully operated up to 100 K.

Optical Properties of Spherical and Oblate Spheroidal Gold Shell Colloids

The surface plasmon modes of spherical and oblate spheroidal core-shell colloids composed of a 312 nm diameter silica core and a 20 nm thick Au shell are investigated. Large arrays of uniaxially aligned core shell colloids with size aspect ratios ranging from 1.0 to 1.7 are fabricated using a novel ion irradiation technique. Angle- and polarization-resolved extinction spectroscopy is performed on the arrays. Extinction spectra on spherical particles reveal dipole, quadrupole, and octupole resonances in good agreement with calculations using Mie theory. Optical extinction measurements on oblate spheroidal core-shell show strong red- and blue-shifts for polarizations along major and minor axes, respectively, that increase with size anisotropy. The measured spectral shifts of the dipole, quadrupole, and octupole resonant modes with angle and anisotropy are in good agreement with T-matrix calculations. The data provide insight into the tunable resonant behavior of surface plasmons in oblate spheroidal core-shell particles.

Irradiation Hardening and Microstructure Evolution of Ion-irradiated ODS Ferritic Steels

Abstract Irradiation hardening and microstructural change of oxide dispersion strengthened (ODS) ferritic steels were investigated by using the ion-irradiation technique. The material used for the present study was K3 (16C-2W-0.3Ti-4.6Al-0.4Y2O3) ODS ferritic steel for the application to Generation IV concept advanced reactors and fusion reactors. 6.4 MeV Fe3+ ions were used to irradiate to the K3 ODS steel by using a 1.7 MeV tandem accelerator. The irradiation temperatures were 300°C and 500°C. The nominal displacement damage rate and total displacement damage were 1×10−3 dpa/s and up to 10 dpa at about 600-nm depth from the irradiated surface, respectively. Nano-indentation hardness was evaluated with a Berkovich indenter. After the ion-irradiation at 300°C up to 1 dpa, the normalized nano-indentation hardness (hardness after irradiation/hardness before irradiation) of the K3 ODS steel reached about 1.28 and the value showed no change up to 10 dpa. On the other hand, the ion-irradiation at 500°C up to 10 dpa showed no significant irradiation hardening. TEM observation revealed that dense and fine dislocation loops were formed in the ion-irradiated steels at 300°C, which were probably enough to explain the irradiation hardening.

Formation, Dynamics, and Characterization of Nanostructures by Ion Beam Irradiation

Ion beam irradiation is a potential tool for phase formation and material modification as a non-equilibrium technique. Localized rise in temperature and ultra fast (∼10−12 s) dissipations of impinging energy make it an attractive tool for metastable phase formation. As a matter of fact, a major component of materials science is dominated by ion beam methods, either for synthesis of materials or for its characterization. The synthesis of nanostructures, and their modification by ion beam technique will be discussed in this review article. Formation of nanostructures using ion beam technique will be discussed first. Depending on species (e.g., mass and charge state) and energy range, there are various modes for an energetic ion to dissipate its energy. The role of the electron will also be covered in this article as a basic principle of its interaction with matter, which is same as for an ion. By using a simple reactive ion beam or electron induced deposition, a secondary phase can be nucleated by ion beam mixing techniques, either by using inert gas irradiation or reactive gas implantation on any desired substrate. Nucleation of secondary phase can also be executed by electron irradiation and direct implantation of either negative or positive ions. Post implantation annealing processes are required for the complete growth of clusters formed in most of these ion irradiation techniques. Implantation processes being inherently a non-equilibrium technique, defects always have a role to play in phase formation, amorphization, and beyond (blister formation). When implanted with large energy, even electrons, one of the lightest charged particles, also manifest these properties. Electronic and nuclear energy losses of the impinging charged particle play a crucial role in material modification. Doping a nanocluster, however, is still a controversial topic. Some light will be shed on this topic with a discussion of focused ion beam.

Local-field enhancement and plasmon tuning in bimetallic nanoplanets

A full-interaction electromagnetic approach is applied to interpret the local- and far-field properties of AuAg alloy nanoplanets (i.e. a central cluster surrounded by small "satellite" clusters very close to its surface) fabricated in silica by ion implantation and ion irradiation techniques. Optical extinction spectroscopy reveals a large plasmon redshift which is dependent on the irradiation conditions. Simulations strongly suggest that the peculiar topological arrangement of the satellite clusters is responsible for the observed plasmonic features. Theoretical results also indicate that strong local-field enhancement is obtained between coupled clusters. Calculations for Ag models show that enhancement factors as high as ~100 are readily achievable.

2D spatial control of metal nanoparticles by multi laser-lithography and heavy-ion irradiation

A new method for nanoparticle planar control has been proposed based on optical laser-lithography technique. With this method, the planar spatial resolution of the lithography is improved. Combining the lithography with subsequent ion-irradiation technique, a two-dimensionally (2D) patterned structure of Cu nanoparticles in a silica substrate is obtained with a sub-micrometer spatial resolution. The size of each “spot” is 500×500nm2, and the pitch is 2μm. Planar TEM image and the result of scanning near-field optical microscopy (SNOM) verify the nanoparticle 2D-patterned distribution. Further improvement of the processing may enable 2D nanoparticle patterning with a pitch on a sub-micrometer scale.

Room-temperature growth of carbon nanofibers on plastic substrates

A very simple method to synthesize densely distributed carbon nanofibers (CNFs) on flexible plastic substrates at room temperature with no catalyst is demonstrated. Carbon film was deposited onto polyimide, poly-ethylene-terephthalate (PET) films, Si plates and a Ni mesh, which were then sputtered with obliquely incident Ar + ions at 3 keV at room temperature. Linear-shaped CNFs oriented in the incidence direction of the ion beam grew on the sputtered substrates, as confirmed by scanning (SEM) and transmission electron microscopes (TEM). CNF growth on a PET substrate, which is a non-heat-tolerant plastic, has never been reported so far. CNFs thus grown were characterized as amorphous without a hollow structure. The diameter of CNFs was almost identical (20–30 nm) despite a large difference in CNF length (0.1–4 μm). In addition, the CNF-tipped cones were demonstrated to act successfully as a template to fabricate one dimensional (1-D) zinc oxide (ZnO) nanostructures on a PET substrate. Thus, it was believed that the ion-irradiation technique would open up a new approach to fabricate any kinds of 1-D nanomaterials on flexible substrates at room temperature.

Highly confined electromagnetic fields in arrays of strongly coupled Ag nanoparticles

Linear arrays of very small Ag nanoparticles (diameter ~10 nm, spacing 0–4 nm) were fabricated in sodalime glass using an ion irradiation technique. Optical extinction spectroscopy of the arrays reveals a large polarization-dependent splitting of the collective plasmon extinction band. Depending on the preparation condition, a redshift of the longitudinal resonance as large as 1.5 eV is observed. Simulations of the three-dimensional electromagnetic field evolution are used to determine the resonance energy of idealized nanoparticle arrays with different interparticle spacings and array lengths. Using these data, the experimentally observed redshift is attributed to collective plasmon coupling in touching particles and/or in long arrays of strongly coupled particles. The simulations also indicate that for closely coupled nanoparticles (1–2 nm spacing) the electromagnetic field is concentrated in nanoscale regions (10 dB radius: 3 nm) between the particles, with a 5000-fold local field intensity enhancement. In arrays of 1-nm-spaced particles the dipolar particle interaction extends to over 10 particles, while for larger spacing the interaction length decreases. Spatial images of the local field distribution in 12-particle arrays of touching particles reveal a particlelike coupled mode with a resonance at 1.8 eV and a wirelike mode at 0.4 eV.

Carbon nanotubes: physics and applications

We overview definitions, properties and applications of Carbon nanotubes (CNTs). We describe the CNTs lifecycle: starting with phases and requirements, going through the different synthesis methods, describing then the various purification techniques. The fundamentals of functionalization and the use of defects in CNTs are reviewed, in connection also to ion irradiation techniques. Metal oxides and other semiconducting 1D nanostructures are then considered, before entering the description of the main features of the present status of INFN-LNF research in nanoscience, focusing on CNTs, as well as on aluminium nitride NTs (AlN NTs). We conclude our review by illustrating device application criteria for many applications in different areas of the field of nanotechnology. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Characterising and controlling surface defects

The controlled production of surface defects by ion irradiation and nanoindentation techniques is discussed. The characterisation of novel types of defects is emphasized, among those: quasi two-dimensional dislocation dipoles following coalescence at the surface of the vacancies induced by the irradiation and ‘mesas’ and ‘winding-loops’ as dislocation configurations originated by nanoindentation. The relationship between the latter defects and the onset of crystal plasticity is examined.

Study on irradiation induced corrosion behavior in austenitic stainless steel using hydrogen-ion bombardment

In order to study the basic factors in irradiation assisted stress corrosion cracking (IASCC) of austenitic steels, the effects of displacement damage on the corrosion behavior of type 304 stainless steel were investigated by means of an ion irradiation technique. Solution-annealed specimens was irradiated using 1 MeV protons to 0.1, 0.5 and 1.0 dpa at about 573, 673 and 773 K. Electrochemical potentiokinetic reactivation (EPR) testing was carried out before and after the ion irradiation to clarify the effects of irradiation on corrosion behavior. The specimens irradiated at 773 K showed clear etching at grain boundaries and relatively high reactivation ratio, however, the specimens irradiated at 573 and 673 K showed no clear grain boundary etching. It was suggested that the higher irradiation temperature enhanced the radiation induced segregation near grain boundaries.

The control of in‐plane magnetic anisotropy by ion irradiation

AbstractThe increase of bit density is a critical point in the magnetic storage media. We intend to manipulate the easy axis in ferromagnetic thin films with ion irradiation technique. Co/Pt multilayered films were prepared for the study and then were ion‐irradiated while an external magnetic field was applied to them. In consequence, we get a CoPt alloy film with an in‐plane easy axis and change its direction with an external magnetic field applied during the irradiation. The energetic ion beam let the ferromagnetic film have a new atomic and magnetic structure. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)