Nitrogen Ion Irradiation Research Articles

Surface modification of triacetylcellulose by low-energy nitrogen ions for diaphragm of environmental cell transmission electron microscope

Triacetylcellulose (TAC) was subjected to surface modification by low-energy nitrogen ion irradiation for use as the diaphragm of an environmental cell transmission electron microscope (E-TEM). TAC films formed by the dipping method were placed on Cu grids for E-TEM and then irradiated by nitrogen ions with acceleration voltages of 1.0 and 1.5 kV and with ion doses between 5.9 × 1016 and 1.2 × 1017 ions/cm2. The TAC films were removed by acetone after irradiation and the surface-modified layers at the top were kept for assessment as diaphragms. The thicknesses of the surface-modified layers, which varied depending on the acceleration voltage and dose of the nitrogen ions, ranged from around 12 to 29 nm. X-ray photoelectron spectroscopy revealed that the surface-modified layers mainly consisted amorphous carbon with a nitrogen-to‑carbon atomic ratio of around 1%. These films were transparent to an electron beam accelerated to 300 kV. The pressure resistances of all samples were maintained at around 0.1 MPa.

Graphitization of a Polycrystalline Diamond under High-Fluence Irradiation with Noble Gas and Nitrogen Ions

To analyze the process of the ion-induced graphitization of a polycrystalline diamond, the surfacelayer conductivity and microstructure are studied experimentally after high-fluence irradiation with Ne+, Ar+, N+, and ions with energies of 20–30 keV at irradiation and heat-treatment temperatures ranging from 30 to 720°R in vacuum. After irradiation with argon ions at room temperature and subsequent heat treatment, the resistivity ϱ of a modified layer decreases exponentially with increasing treatment temperature T ht and reaches the graphite value ϱ at Tht = 700°R. Such a temperature T ht is insufficient for surface-layer graphitization by nitrogen ions. The increase in the diamond temperature under irradiation leads to a decrease in the ion-induced thermal graphitization temperature T g by several hundred degrees. It is found that the temperature T g is almost coincident with the corresponding temperature Ta of the dynamic annealing of radiation-induced damage in graphite. Analysis of the irradiated layer using Raman spectroscopy reveals the heterogeneous structure of the modified layer containing graphite and amorphous phases, the ratio between which correlates with the layer resistivity. Under argon-ion irradiation at diamond temperatures of 500°R or more, an increase in ϱ of the irradiated layer is observed, which is related to the formation of nanocrystalline graphite. This effect is not observed under nitrogen-ion irradiation.

Structural characterization of indium-rich nanoprecipitate in InGaN V-pits formed by annealing**Project supported by the National Natural Science Foundation of China (Grant Nos. 61604080, 61574079, 61634002, and 61474060), Natural Science Foundation of Jiangsu Province, China (Grant No. BK20160883), University Science Research Project of Jiangsu Province, China (Grant Nos. 16KJB140011 and 14KJB510020), and NUPTSF, China (Grant No. NY214154).

InGaN layers capped with GaN were annealed at 550 °C for 1 hour. During annealing, cracks appeared and dissolved InGaN penetrated through the microcracks into the V-pits to form indium-rich nanoprecipitates. Some precipitates, in-situ annealed under nitrogen ion irradiation by MBE, were confirmed to be cubic GaN on the tops of precipitates, formed by nitriding the pre-existing Ga droplets under nitrogen ions irradiation.

Compaction of polydimethylsiloxane due to nitrogen ion irradiation and its application for creating microlens arrays

In this work the change in the surface topography of polydimethylsiloxane (PDMS) due to irradiation with 10.5MeV N4+ ion microbeam is investigated. Parallel stripes with different widths and different gaps between the stripes were irradiated. The heavy ion beam induced physical and chemical processes caused shrinkage of the irradiated structures. The degree of compaction, and its relation to the irradiation fluence and pattern was studied by means of atomic force microscopy (AFM). Exploiting the compaction effect, arrays of microlenses with different diameters were designed and fabricated in PDMS. We show that regular microlenses can be produced by the adjustment of their size and irradiation fluence. The focal length of the lenses can be tuned with the diameter of the lens and with the delivered ion fluence.

Surface Modification of PTFE Using Low‐Energy Nitrogen Ion Irradiation: Improvement in Adhesive Strength on Modification of Deep Modifying Layer

SUMMARYPolytetrafluoroethylene (PTFE) has the best properties as a material of high‐frequency PC board. However, it has low adhesion force for using cabling material. In order to improve adhesion force, we studied on surface modification of PTFE by using nitrogen ion irradiation. As a result, peel strengths of PTFE improved up to 900 N/m to amount of treatment time. On the other hand, surface energy did not increase. From here onward, improved peel strengths on modified surface could be forecasted because of a change that is binding state of modified layer. The compositions of surface on samples after peel test were analyzed so as to prove the hypothesis. As a result, adhesive/PTFE system occurred to destruction in deep portion of modified layer. Moreover, binding of oxygen could be existed with long treatment time. Therefore, it was suggested that the brittle layer of deep modifying layer needs to be modified for the improvement of adhesive strength.

Effects of thermal treatment on structure, surface microstructure and optical properties of nitrogen-ion irradiated nanoparticle thin films

Abstract In this paper, we studied the effects of ion irradiation and annealing treatment on the ZnO thin films. ZnO thin films were first prepared on sapphire substrate by rf-magnetron sputtering technique, followed by nitrogen ion irradiation and annealing treatment. The crystallographic properties, surface morphology and optical properties changed after nitrogen ion irradiation and annealing treatment, which were investigated by X-ray diffraction, scanning electron microscopy and absorption spectroscopy.

Raman and morphology visualization in epitaxial graphene on 4H-SiC by Nitrogen or Argon ion irradiation

Graphene is a one-atom-thick planar sheet of carbon atoms that are densely packed into a honeycomb crystal lattice and is attracting tremendous interest since being discovered in 2004. Epitaxial growth of graphene on silicon carbide (SiC) is an effective method to obtain high quality layers. In this work, the effects of irradiation on epitaxial SiC/graphene were studied. The samples were irradiated with Nitrogen and Argon ions at an energy of 200keV and different fluence with 4×1012 ions/cm2 to 1×1013 ions/cm2. The results of Raman measurements indicate that ion beam irradiation causes defects and disorder in the graphene crystal structure, and the level of defects increases with increasing ion fluence. Surface morphology images are obtained by atomic force microscope (AFM). This work is valuable for the potential application of epitaxial graphene on SiC in the field of optoelectronics devices.

Nano-welding and junction formation in hydrogen titanate nanowires by low-energy nitrogen ion irradiation

Crystalline hydrogen titanate (H2Ti3O7) nanowires were irradiated with N+ ions of different energies and fluences. Scanning electron microscopy reveals that at relatively lower fluence the nanowires are bent and start to adhere strongly to one another as well as to the silicon substrate. At higher fluence, the nanowires show large-scale welding and form a network of mainly ‘X’ and ‘Y’ junctions. Transmission electron microscopy and Raman scattering studies confirm a high degree of amorphization of the nanowire surface after irradiation. We suggest that while ion-irradiation induced defect formation and dangling bonds may lead to chemical bonding between nanowires, the large scale nano-welding and junction network formation can be ascribed to localized surface melting due to heat spike. Our results demonstrate that low energy ion irradiation with suitable choice of fluence may provide an attractive route to the formation and manipulation of large-area nanowire-based devices.

Irradiation-induced TiO2 nanorods for photoelectrochemical hydrogen production

In this work, well-ordered nanorods were fabricated on the surface of TiO2 thin films deposited on Ti sheets by an ion irradiation method using nitrogen ion irradiation with the energy of 65 keV to a fluence of 1 × 1017 ions/cm2. These TiO2 nanorods are about 120 nm in length and 20–40 nm in diameter. After post-irradiation annealing at 500 °C in O2, the nanorod array photoelectrode displays largely enhanced performance for photoelectrochemical (PEC) water splitting compared to that of the un-irradiated TiO2 thin films with a planar structure. The influences of the irradiated ion energy on the morphology and photocurrent density of the nanorods were investigated. The 65 keV N+ irradiated TiO2 thin films shows a higher photocurrent density than those of the 45 and 85 keV N+ irradiated TiO2 thin films. We also discussed the influence of annealing conditions on the PEC performance of TiO2 nanorods, and it was found that the nanorods annealed at 600 °C in vacuum produce a much higher photocurrent density of 0.6 mA/cm2 at 0.8 V (vs. a saturated calomel electrode), which is about 7 times higher than that of the nanorods annealed in oxygen. This work proposes that ion irradiation combination with thermal annealing in vacuum could be an effective approach for developing nanostructured materials for water splitting.

窒素イオン照射を用いたPTFEにおける剥離強度のイオンエネルギー依存性

窒素イオン照射を用いたPTFEにおける剥離強度のイオンエネルギー依存性

Adhesive hydrophobicity of Cu2O nano-columnar arrays induced by nitrogen ion irradiation.

Low energy nitrogen ions are used in this work to manipulate wetting properties of the surface of the array of Cu2O nano-columns, which yields remarkable results. The nano-columnar thin films were grown on a highly conductive silicon surface by a sputter deposition technique. The films were irradiated at two different fluences of 5 × 10(15) and 1 × 10(16) ions per cm(2), respectively. With increasing fluence the shape of column tip changes, columns are bent and porous channels between columns are clogged up. While the surface of the pristine sample is hydrophilic, the irradiated surface turns into hydrophobic but having adhesion properties. We have analysed the structural and chemical properties of the surface in detail to understand the initial and modified wetting properties. Furthermore, the temporal evolutions of different droplet parameters are investigated to realize the interactions between the water droplet, the sample surface and the atmosphere. We envisage that such modified surfaces can be beneficial for transport of a small volume of liquids with minimum loss and spectroscopic studies, where a small amount of water droplet is available for measurements.

Fourier transform infrared spectroscopy analysis of thin boron nitride films prepared by ion beam assisted deposition

AbstractThin boron nitride (BN) films were synthesized by ion beam assisted deposition (IBAD). From Fourier transform infrared spectroscopy (FTIR) analysis results, it was found that: the films with the co‐presence of explosion‐phase BN (E‐BN) and sp2‐bonded hexagonal BN (h‐BN), and those with pure h‐BN were formed in the respective substrate temperature regions of 20–85 °C and 350–400 °C, under nitrogen ion irradiation (ion energy from 500 to 1000 eV), while the substrate temperature at 400 °C and mixed nitrogen and argon ion irradiation were necessary for the formation of sp3‐bonded cubic BN (c‐BN). To our knowledge, the E‐BN phase was formed firstly by IBAD in this study. The crystalline phase identification through the FTIR results was in line with X‐ray diffraction results. The shift of the c‐BN peak position is usually attributed to remaining compressive stress in the film. In this work, the downward shift of the c‐BN peak position and the broadening of the c‐BN peak, which were observed when the film thickness increased, can be interpreted using a phenomenological description of structural disordering in the c‐BN sites. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Role of Ion Beam Irradiation and Annealing Effect on the Deposition of AlON Nanolayers by Using Plasma Focus Device

AlON nanolayers are synthesized on Al substrate by the irradiation of energetic nitrogen ions using plasma focusing. Samples are exposed to multiple (5, 10, 15, 20 and 25) focus shots. Ion energy and ion number density range from 80 keV to 1.4 MeV and 5.6×1019 m−3 to 1.3×1019 m−3, respectively. Moreover, the effect of continuous annealing (473 K and 523 K) on an AlN surface layer synthesized with 25 focus shots is also examined. The main features of the X-ray diffraction (XRD) patterns with increasing focus shots are: (i) variation in the crystallinity of AlN along (111), (200) and (311) planes, (ii) increasing average crystallite size of AlN (111) plane, and (iii) stress relaxation observed in AlN (111) and (200) planes. The crystallinity of AlN surface layer is comparatively better at 473 K annealing temperature. A broadened diffraction peak related to an aluminium oxide phase showing weak crystallinity is observed for 15 focus shots while non-bounded oxides are present in all other deposited layers. Raman and Fourier transform infrared spectroscopy (FTIR) analysis confirm the presence of AlN and Al2O3 for the surface layer annealed at 473 K temperature. Raman analysis shows that the overlapping of AlN and Al2O3 results in the development of residual stresses. Scanning electron microscope (SEM) results demonstrate that the formation of rounded grains (range from 20 nm to 200 nm) and variations in their microstructures features depend on the increasing number of focus shots. Decomposition of larger clusters into smaller ones is observed.

Effect of the surface modification of titanium nickelide by nitrogen and titanium ions on the adhesion to a nanosized carbon coating deposited by a pulsed vacuum-arc method

The adhesion strength of nanosized carbon coatings deposited by a pulsed vacuum-arc method to the titanium nickelide substrate preliminarily modified by the irradiation of nitrogen and titanium ions is studied. Preliminary modification of the titanium nickelide surface is found to prevent the swelling and exfoliation of a carbon coating.

Effect for hydrogen, nitrogen, phosphorous, and argon ions irradiation on ZnO NWs

Zinc oxide (ZnO) nanowires (NWs) are exposed to energetic proton (H+), nitrogen (N+), phosphorus (P+), and argon (Ar+) ions to understand the radiation hardness and structural changes induced by these irradiations. High-resolution transmission electron microscopy is utilized to see the irradiation effects in NWs. Multiple doses and energies of radiation at different temperatures are used for different set of samples. The study reveals that wurtzite (crystalline)-structured ZnO NWs experience amorphization, degradation, and morphological changes after the irradiation. At room temperature, deterioration of the crystalline structure is observed under high fluence of H+, N+, and P+ ions. While for ZnO NWs, bombarded by Ar+ and P+ ions, nano-holes are produced. The ZnO NWs surfaces also show corrugated morphology full of nano-humps when irradiated by Ar+ ions at 400 °C. The corrugated surface could serve as tight-holding interface when interconnecting it with other NWs/nanotubes. These nano-humps may have the function of increasing the surface for surface-oriented sensing applications in the future.

Annealing Effects after Nitrogen Ion Casting on Monolayer and Multilayer Graphene

The modification of the electronic properties of a coverage-dependent graphene layer by nitrogen ions irradiation was investigated using core-level photoemission spectroscopy (CLPES). Here we describe preparation of monolayer and multilayer epitaxial graphene (EG) functionalized by nitrogen ions irradiation with 100 eV to minimize the damage of graphene layer as we annealed up to 1300 K to track the surface property changes using CLPES. As a result, on the monolayer EG, we found that pyridinic nitrogen mainly existed on the surface. On the multilayer EG, we observed the formation of graphitic nitrogen remaining as a major species confirmed using N 1s core-level spectra. Through a work function change (ΔΦ) measurement, both systems indicated p-type doping properties with 4.71 (monolayer EG) and 4.87 eV (multilayer EG) of work function values after N2 ion irradiation. Interestingly, we observed that monolayer EG maintained its p-type doping character, whereas multilayer EG changed the doping character from p-type to n-type as we annealed both systems up to 1300 K due to the discrepancy of the electron charge transfer. We will systematically demonstrate these variations of electronic properties for both monolayer and multilayer EG.

Improvement in Adhesive Strength of PTFE using Nitrogen Ion Irradiation

Improvement in Adhesive Strength of PTFE using Nitrogen Ion Irradiation

Surface Modification of PMMA by Ion Irradiation

Surface hardness of PMMA (poly methyl methacrylate) was improved by low energy nitrogen ion irradiation. It was confirmed that hardness on the surface was improved by increasing the acceleration voltage of ion irradiation. It was thought that this was because the projected range became long and region of cross-link formation became thick. However the depth of cross-link formation was not confirmed. Then, distribution of the cross-link structure in the direction of depth was measured by using XPS (X-ray Photoelectron Spectrometer).As a result, it was confirmed that the surface hardness was improved on the formation depth of the C-N-C bonds. From this, it was suggested that the modification layer of the cross-link structure became thick the surface hardness became strong.

Swift nitrogen ion irradiated waveguide lasers in Nd:YAG crystal

We report on the fabrication, fluorescence and laser properties of optical waveguides by swift nitrogen ion irradiation in Nd:YAG crystals. The confocal micro-luminescence investigations have concluded that the fluorescence features of the bulk material have been well preserved in the waveguide. Under 808 nm optical end-pumping, continuous-wave (cw) laser oscillation at 1064.2 nm has been demonstrated with laser slope efficiencies of 16% and pump power thresholds of 38.3 mW.

Improvement of field emission performance on nitrogen ion implanted ultrananocrystalline diamond films through visualization of structure modifications

The relationship between the electron field emission properties and structure of ultra-nanocrystalline diamond (UNCD) films implanted by nitrogen ions or carbon ions was investigated. The electron field emission properties of nitrogen-implanted UNCD films and carbon-implanted UNCD films were pronouncedly improved with respect to those of as-grown UNCD films, that is, the turn-on field decreased from 23.2 V/μm to 12.5 V/μm and the electron field emission current density increased from 10E−5 mA/cm 2 to 1 × 10E−2 mA/cm 2. The formation of a graphitic phase in the nitrogen-implanted UNCD films was demonstrated by Raman microscopy and cross-sectional high-resolution transmission electron microscopy. The possible mechanism is presumed to be that the nitrogen ion irradiation induces the structure modification (converting sp 3 -bonded carbons into sp 2 -bonded ones) in UNCD films.