Energy Nitrogen Ion Research Articles

Contribution of Cross-linking Structure Introduction on Surface Hardness Improvement of PMMA by Nitrogen Ion Irradiation

Surface modification of PMMA (polymethylmethacrylate) was carried out by irradiation of low energy nitrogen ion and/or electron, which is expected to improve the surface hardness by introduction of a thin modified layer. Surface hardness was measured by using the nanoindentation test. To clarify the structure and the properties of the modified layer, composition and chemical bonds were analyzed using XPS (X-ray photoelectron spectroscopy) and FT-IR (Fourier transform infrared spectrometer).From these results, it was confirmed that surface hardness increased and some chemical bonds including nitrogen was introduced. Thus, it was suggested that cross-linking structure including nitrogen atom contributed on the increase of surface hardness.

A Study of Mutation Breeding of High-Yielding Tryptophanase Escherichia coli by Low-Energy N+ Ion Beam Implantation

Low energy ion beam has been widely applied in microbe breeding, plant breeding, gene transfer and cell modification. In this study, the Escherichia coli (E.coli) strain producing tryptophanase was irradiated by a low energy nitrogen ion beam with an energy of 10 keV at a fluence of 13 × 1014 N+/cm2 when glycerin at a 15% concentration was used as a protector. The effect on the biomass of E. coli after N+ implantation was analyzed in detail by statistic methods. The screening methods used in this study were proven to be effective. After continuous mutagenicity, a high-yield tryptophanase strain was selected and both its biomass and enzymatic activity were higher than those of the parent strain. The results of scale-up production showed that the biomass could reach wet weight 8.2 g/L and 110 g L-tryptophan could be formed in the volume of the 1l enzymatic reaction system.

Nitrogen Ion Induced 2D-GaN Layer Formation of GaAs (001) Surface

This study demonstrates the formation of two-dimensional GaN on GaAs (001) surface by bombardment of nitrogen ions at room temperature. In this work the ion induced nitridation of GaAs (001) surface using nitrogen ion beam of different energies (range from 250 eV to 5 keV) has been investigated using in-situ X-ray Photoelectron Spectroscopy (XPS). A Ga rich surface produced by Art ion etching, promotes initial nitridation. Using nitrogen ion of different energies of constant fluence performs the nitridation. The nitridation suggests that the degree of nitridation increase as the nitrogen ion energy increases up to 3 keV and then attains saturation. The core level and valance band spectra were monitored to observe the chemical and electronic changes as a function of nitrogen ion beam energy. It is observed that Ga(3d) core level peak shifts during nitridation and N(1s) core level spectra shows that the intensity of the nitrogen peak increases and the Ga (LMM) auger peak shifts towards the higher binding energy, reveal the forming of N bonds with Ga by replacing the Ga-As bonds, forming GaN.

Characterization of Nitrogen-Doped Carbon Nanotubes by Atomic Force Microscopy, X-ray Photoelectron Spectroscopy and X-ray Absorption Near Edge Spectroscopy

In this work, we perform a comparative study on single-walled carbon nanotubes (CNT) before and after low energy nitrogen ion bombardment (70 eV and 25 x 10-6 A/cm2) at room temperature. The morphology and the mechanical properties were studied by Atomic Force Microscopy (AFM). The bonding configuration of the N-doped CNTs was established by X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Near Edge Spectroscopy (XANES). Single-walled carbon nanotubes were prepared using non-intrusive methods and deposited onto silicon substrates. For the spectroscopic studies, samples with a high concentration of CNTs were analyzed. XPS reveals different chemical states for carbon related to the incorporation of nitrogen. XANES confirms the hexagonal structure of the CNTs, resembling the bonding structure of hexagonal carbon nitrides. AFM images confirm that the CNTs were not destroyed after low energy N2+. The morphology of the original nanotubes maintains after nitrogen ion bombardment except for the incorporation of some pearl-shaped decoration, probably due to the adsorption of some contaminants or to deposition of re-sputtered material. Whereas CNTs improve their adherence to the substrate, this extra granularity on the CNT is easily removed even with the AFM tip. In conclusion, spectroscopic measurements and mechanical properties made clear information on the changes produced on CNT after nitrogen incorporation.

Biomedical aspects of ion bombardment of polyethylene

Press-moulded ultra-high molecular weight polyethylene (UHMWPE) samples were subjected to ion bombardment and effects of the modification studied. Helium, nitrogen, argon and silver ions of energy 65–150 keV and fluences in the range of 1 × 10 14 to 3 × 10 16/cm 2 were applied. The consequences of the modification were studied with FT-IR, Raman and AFM techniques, contact angle measurements, bacteriostaticity and thrombogeneity tests. Surface layer oxidation, graphitization and changes to the surface geometry lead to increase of the surface energy. Modified surface exhibits bacteriostatic properties particularly for higher ion fluences. Aggregation of blood platelets on polymer surface subjected to ion bombardment is limited.

Mutation Breeding of β-carotene Producing Strain B. trispora by Low Energy Ion Implantation

Ion beam bioengineering technology as a new mutation approach has been widely used in the biological breeding field. In this paper the application of low energy nitrogen ion implantation in the β-carotene producing strain, Blakeslea trispora(–) was investigated. The effects of different fermentation conditions on β-carotene production by a high yield strain were examined. Results showed that two β-carotene high yielding strains B.trispora(–) BH3–701 and BH3–728 were screened out and the averaged production of β-carotene was raised by 178.7% and 164.6% respectively after five passages in the shaking flasks. Compared with the original strain, the highest yield strain BH3–701 was potent in accumulating β-carotene, especially in the later stage, and greatly increased production efficiency.

Structure Change of PTFE by Low Energy Ion Irradiation -Restraint of Structure Collapse by Cross-linking Structures-

The authors irradiate low energy nitrogen ion (100eV) on PTFE (poly-tetra-fluoro-ethylene) for surface modification. However, PTFE cannot anticipate adhesive strength improvement because it is collapse type polymer and weariness of surface occurs by ion irradiation. We paid attention to cross-linked structure to solve this problem.By this study introduce below, PTFE was changed collapse type polymer into cross-linked type polymer by rising temperature above the glass transition in the case of ion irradiation. As a result, the formation of the CF3 combination was restrained and collapse phenomenon was prevented by ion irradiation above the glass transition. In addition, it was suggested that cross-linked structure is effective for adhesive strength improvement by convolution of C1s spectrum and density profile.

Growth of InN thin films by modified activated reactive evaporation

Indium nitride films have been grown using modified activated reactive evaporation (MARE). The films were grown on glass and silicon substrates at room temperatures, i.e. without any intentional substrate heating. In this technique, the substrates were kept on the cathode instead of the grounded electrode and hence subjected to low energy nitrogen ion bombardment leading to highly c-axis oriented films. The photoluminescence (PL) and Raman spectrum shows significant improvement in the quality of the films compared with conventional activated reactive evaporation. The band gap measured from the room temperature PL was found to be 1.9 eV. Very high growth rates can be achieved in the MARE growth technique. The modification in the activated reactive evaporation technique may have a large impact on the growth of various compounds such as metal oxides.

Study of Biological Effects of Low Energy Ion Implantation on Tomato and Radish Breeding

Biological effects of 30 keV low energy nitrogen ion implantation on the seeds of five types of tomato and one type of radish were investigated. Results showed that low energy ions have different effects on different vegetables. The whole dose-response curve of the germination ratio did not take on "the shape of saddle", but was a rising and falling waveform with the increase or decrease in ion implantation. In the vegetable of Solanaceae, two outstanding aberrant plants were selected from M1 of Henan No.4 tomato at a dose of 7 × 1017 nitrogen ions/cm2, which had thin-leaves, long-petal and nipple tip fruit stably inherited to M7. Furthermore the analysis of the isozyme showed that the activity of the mutant tomato seedling was distinct in quantity and color. In Raphanus sativus L., the aberrances were obvious in the mutant of radish 791 at a dose of 5 × 1017 nitrogen ions/cm2, and the weight of succulent root and the volume of growth were over twice the control's. At present, many species for breeding have been identified in the field and only stable species have been selected for the experiment of production. It is evident that the low energy ion implantation technology has clear effects on vegetables' genetic improvement.

Monte Carlo simulation of nitriding in iron by a mixing technology with laser and plasma beams

Abstract A program is modeled to describe nitriding depth by a new mixing laser and plasma beams nitriding (LPN) technique. The model extends the transport of ions in matter (TRIM) program by adding temperature and energy factors into the energy function. The nitriding depths and nitrogen distribution in substrate were calculated by Monte Carlo program. There is a good agreement between calculation and experiment results at different laser energy intensities, scanning velocities and nitrogen ion energies respectively. Moreover, the nitriding process diagrams by LPN technique are shown from calculation results.

Tool steel ion beam assisted nitrocarburization

The nitrocarburization of the AISI-H13 tool steel by ion beam assisted deposition is reported. In this technique, a carbon film is continuously deposited over the sample by the ion beam sputtering of a carbon target while a second ion source is used to bombard the sample with low energy nitrogen ions. The results show that the presence of carbon has an important impact on the crystalline and microstructural properties of the material without modification of the case depth.

Nitrogen ion energy dependencies of dielectric constants and compositions of barium carbide–barium nitrate mixed films deposited on silicon wafers by an ion beam assisted deposition technique

Thin BaC6–BaN2O4 mixed films with a thickness of 25–60nm were deposited on Si wafers by evaporating BaCO3 with electron beams and simultaneously applying a mixed beam of N2 molecules and nitrogen ions (an ion beam assisted deposition technique). BaC6 films deposited on Si wafers by evaporating only BaCO3 had low-k values, such as 1.3. In contrast, mixed films containing a small amount of BaC6 and a large amount of BaN2O4 had mild k values, such as 5.6.

Growth and erosion of amorphous carbon (a-C:H) films by low-temperature laboratory plasmas containing H and N mixtures

Growth and erosion of amorphous hydrogenated carbon (a-C:H) films from nitrogen-containing gas mixtures was studied in an electron-cyclotron-resonance low-temperature plasma. Deposition and erosion rates were measured as a function of nitrogen admixture and ion energy. At low energy, N2 addition to methane plasmas causes a reduction of the deposition rates that does not exceed significantly the expected reduction due to dilution. At higher ion energies the deposition rate reduces further and finally switches to net erosion. Erosion of a-C:H films in N2/H2 mixtures is much more efficient than in pure H2 and N2. The erosion rate drops with increasing N2 admixture almost proportional to the total ion flux if the substrate is at floating potential. For higher ion energies the erosion rate dramatically increases and shows a clear maximum at around 25% N2 flow ratio.

Energy and charge distributions of fast nitrogen ions reflected from metal surface at grazing incidence

Energy and charge distributions of ions scattered under grazing incidence conditions from metallic surfaces are studied theoretically. The energy distribution of scattered ions with fixed charge is calculated by the energy distribution of reflected ions with equilibrium charge and charge fraction of these ions. The charge fractions of scattered ions are estimated by charge exchange cross sections. We calculated the energy and charge distributions of 1MeV nitrogen ion scattered from platinum surface. The calculation results are in qualitative agreement with experimental data.

Nano-mechanical properties of BCN/CN/BN multilayer films

Hard coatings based on BCN/CN/BN multilayer films were deposited on Si substrates using a double ion beam sputtering system. The multilayers were obtained by sequential sputtering of BN, C and B 4C targets and simultaneous bombardment of the growing films with low energy nitrogen ions. The multilayers were characterized by Auger electron spectroscopy (AES) depth profiles in order to get a quantitative analysis of the components in the different layers. In the interface BCN/CN, Factor Analysis was used to deconvolute the different chemical states of the components and to evaluate the physical and chemical characteristics of the multilayer with respect to their practical applications. In this work, we have studied the composition, morphology, hardness and wear resistance of the films. The mean grain size of the structures of the different coatings, as well as the root mean square (RMS) surface roughness, was measured by AFM.

Flow Energy Control of Nitrogen Ions Generated by Electron Cyclotron Resonance

The flow energy of nitrogen ions produced by an electron cyclotron resonance (ECR) discharge is controlled by electrostatic acceleration in a plasma synthesis method. The source consists of an ion production region using ECR and a plasma synthesis region. Two grids for potential control and electron reflection of the ion production region, and an electron emitter with mesh shape are installed. In the synthesis region, electrons emitted from the emitter and ions accelerated by electrostatic potential difference between these regions are synthesized, which yields the generation of ion flow in the synthesis region. The electron temperature in the plasma synthesis region can be reduced to about 0.5 eV because of a reflection of high-energy electrons in the ion production region and a supply of thermionic electrons. In addition, it is observed that the density ratio of nitrogen atomic to molecular ions in the synthesis region markedly increases compared with that in the ion production region.

Raman and infrared spectroscopy studies of carbon nitride films prepared on Si (100) substrates by ion beam assisted deposition

Carbon nitride films prepared by ion beam assisted deposition were studied by Raman and infrared spectroscopy, as a function of nitrogen ion energy (200, 400, and 600 eV) and the ion to atom arrival rate ratio R(I/A) ranging from 0.9 to 2.5. The composition ratio N/C in the film determined by elastic recoil detection analysis was found to be proportional to R(I/A); however, the film growth is possible only if R(I/A) is smaller than a critical value of chemical sputtering yield. This value was found to be 0.21. The maximum value of N/C obtained was 0.9 (47 at.% of nitrogen) for the film deposited with ion energy of 400 eV. In order to understand the effect of nitrogen incorporation on the structure of the films, the parameters were determined from the Raman spectra analysis of the films and found to show strong dependences of the nitrogen content in the films; the behaviors of the G peak position and width, and I D/I G ratio are correlated with the structure changes in the films.

A Mutant of Bacillus Subtilis with High-Producing Surfactin by Ion Beam Implantation

In order to generate a mutant of Bacillus subtilis with enhanced surface activity through low energy nitrogen ion beam implantation, the effects of energy and dose of ions implanted were studied. The morphological changes in the bacteria were observed by scanning electron microscope (SEM). The optimum condition of ions implantation, 20 keV of energy and 2.6×1015N+/cm2 in dose, was determined. A mutant, B.s-E-8 was obtained, whose surface activity of 50-fold and 100-fold diluted cell-free Landy medium was as 5.6-fold and 17.4-fold as the wild strain. The microbial growth and biosurfactant production of both the mutant and the wild strain were compared. After purified by ultrafiltration and SOURCE 15PHE, the biosurfactant was determined to be a complex of surfactin family through analysis of electrospray ionization mass spectrum (ESI/MS) and there was an interesting finding that after the ion beam implantation the intensities of the components were different from the wild type strain.

Response of a delta-doped charge-coupled device to low energy protons and nitrogen ions

We present the results of a study of the response of a delta-doped charge-coupled device (CCD) exposed to ions with energies less than 10keV. The study of ions in the solar wind, the majority having energies in the 1–5keV range, has proven to be vital in understanding the solar atmosphere and the near Earth space environment. Delta-doped CCD technology has essentially removed the dead layer of the silicon detector. Using the delta-doped detector, we are able to detect H+ and N+ ions with energies ranging from 1to10keV in the laboratory. This is a remarkable improvement in the low energy detection threshold over conventional solid-state detectors, such as those used in space sensors, one example being the solar wind ion composition spectrometer (SWICS) on the Advanced Composition Explorer spacecraft, which can only detect ions with energies greater than 30keV because of the solid-state detector’s minimum energy threshold. Because this threshold is much higher than the average energy of the solar wind ions, the SWICS instrument employs a bulky high voltage postacceleration stage that accelerates ions above the 30keV detection threshold. This stage is massive, exposes the instrument to hazardous high voltages, and is therefore problematic both in terms of price and its impact on spacecraft resources. Adaptation of delta-doping technology in future space missions may be successful in reducing the need for heavy postacceleration stages allowing for miniaturization of space-borne ion detectors.

Hydrogen permeability and erosion behavior of W–Pd bimetallic systems

The erosion behavior of W–Pd bimetallic systems has been investigated for both hydrogen-saturated (H/Pd ∼ 0.65) and unsaturated states during impact of a steady-state nitrogen plasma from a mirror Penning discharge. An essential decrease by factors of about 2–5 in the erosion rate of W was observed for hydrogen-saturated W–Pd samples in the nitrogen ion energy range from 0.8 to 1.6 keV. Possible reasons for this erosion behavior are discussed. Isotherms and isobars of hydrogen permeability through W–Pd systems were measured in the temperature range of 573–973 K and hydrogen pressure range of 1.33 × 10 2 to 10 5 Pa. It is shown that the limiting stage of permeation process is, most likely, the diffusion in the W film. The activation energy of hydrogen permeability was determined to be ∼12 kJ/mol, this being much lower than the literature data for bulk tungsten at molecular hydrogen-driven permeation. Possible mechanisms are suggested and analyzed to explain the observed decrease in the activation energy of hydrogen penetration through W–Pd systems.