Increasing Ion Beam Energy Research Articles

Copper K-shell x-ray emission induced by the impact of ion beam from an electron cyclotron resonance ion source

The K-α and K-β x-ray emission (at 8.05keV and 8.9keV respectively) produced from a copper target by the impact of 25keV hydrogen (H+) and nitrogen (N+) ion beams, and 200keV for argon (Ar+8) beams from an electron cyclotron resonance ion source (ECRIS), has been studied experimentally. The K-α x-ray line intensity exhibited an increase with increasing ion beam energy with a scaling law IK-α∝Eγ, where the scaling exponent γ was 4.0, 4.2, and 4.1 for hydrogen, nitrogen, and argon ion beam respectively. The results can be explained by considering the K-shell ionization cross-section for ion impact. The peak to background ratio of x-ray line intensity was observed to increase rapidly with the ion beam energy and highest ratio of 6×105 was observed for hydrogen ions. The study is important for optimizing ECRIS for generating a low cost, long life x-ray source for applications in material science.

Homogeneous liquid crystal orientation on ion beam exposure TiO2 surfaces depending on an anisotropic dipole field

We studied homogeneous liquid crystal (LC) alignment properties on ion-beam (IB) irradiated TiO2 films deposited by the electron beam evaporation method. Stable homogeneous LC alignment on a TiO2 surface resulted from IB irradiation energy over 1800 eV. X-ray photoelectron spectroscopy analyses showed that Ti4+ 2p3/2 and Ti4+ 2p1/2 peaks were increased with increasing IB energy. Assuming that the increased peaks produced anisotropy dipole fields in the direction of the IB exposure process, we confirmed that the increasing IB energy induced strengthened the surface energy for entirely clear and stable LC molecule orientation. The voltage-transmittance characteristics of the twisted-nematic cell on the TiO2 surface indicate that the TiO2 film has potential for use as the LC alignment layer.

Surface-restructuring behavior of aged PTFE irradiated by a high-flux nitrogen ion beam

Polytetrafluoroethylene (PTFE) was irradiated by a high-flux nitrogen ion beam. The influence of experimental parameters was investigated by varying ion beam energy from 2 to 20 keV with the same flux of 1.4×10 17 ions/cm 2. XPS, SEM, AFM, and wettability were employed to study structures and properties of the treated PTFE samples. All of the as-irradiated samples were aged in air for 1 year. After aging, five chemical bonds, CF 3, CF 2, CF, CO, and carbon bonds were observed on the surfaces of the aged samples. The intensities of various chemical bonds changed with increasing ion beam energy. The surface-restructuring behavior was observed on the surfaces of the aged samples irradiated by ion beam with energies of 2 and 5 keV. The surface roughness and water droplet contact angle of the aged PTFE samples irradiated with 2 and 5 keV ion beams improved obviously, and those of the aged PTFE samples irradiated with 10 and 20 keV ion beams kept basically no change. The experimental results suggest that the ion beam energy strongly affected the surface chemical bond, microstructure, and wettability of the aged PTFE samples.

AFM study of the effect of direct negative Ni ion beam energy on the evolution of Ni nanoislands

The influence of secondary negative Ni ion beam energy on the evolution of crystalline grains as a function of ion beam energy was investigated. Prior to deposition, we also characterized the property of direct Ni − ion beam source such as secondary Ni − ion yield, ion energy spread, and deposition rate and then by atomic force microscopy analyses we have characterized the morphology and roughness of the ion beam bombarded surface. Increasing the ion beam energy resulted in an increase in the surface roughness which can be explained by the growth of separated cone shaped grains. However, beyond 75 eV roughness decreased by the reduction of grain size due to many nucleation sites. Thin film deposition rate also decreased as increasing ion beam energy.

Characteristics of a direct negative carbon ion beam source and AFM observations of DLC film

The properties of a direct negative carbon ion beam source were characterized to optimize the conditions for deposition of diamond-like carbon films on Si substrates at room temperature. The effect of secondary negative carbon ion beam energy on deposition rate, surface roughness and tribological properties of the DLC films were studied. During deposition, approximately 30% of the all sputtered carbon atom is negatively ionized at the target surface, with a surface ionization and carbon ion yield strongly dependent on the primary Cs + ion dose and bombarding energy. Also, Cs sputter generated carbon ion has a narrow ion beam energy spread. The measured results of atomic force microscopy (AFM) showed that surface roughness decreased with increasing ion beam energy due to increased adatom mobility and resputtering of weekly bonded carbon atom. However, beyond 200 eV, surface roughness increased steeply. It is considered that the kinetic energy of carbon ions contributes to form the very flat surface but that the excessive energy results in damage to the DLC films. The friction coefficient of the DLC films was evaluated using a ball on disk tribotester. It was found that the surface roughness has an effect on the friction coefficient.

Mechanical properties and residual stress in AlN films prepared by ion beam assisted deposition

Aluminum nitride (AlN) thin films were prepared by the ion beam assisted deposition method. The effect of the nitrogen ion beam energy on mechanical properties and residual stresses was studied by changing the ion beam energy from 0.2 to 1.5 keV, resulting in a different film microstructure. Mechanical properties were examined by a nano-indentation method and residual stresses were evaluated from the film curvature measured by an optical cantilever system. All of the films were found to be in a compressive stress state, the value of the stress decreasing with the ion beam energy. It was also observed that the films became soft and plastic with increasing ion beam energy. To study the effect of thermal treatment on the relaxation of residual stresses, films prepared with the ion beam energies of 0.2 and 1.5 keV, which show a columnar and a granular structure, respectively, were annealed in nitrogen at 500 °C. It was found that the granular structure film is relaxed more easily than the columnar structure film.

Primary beam energy dependence of properties in ion beam sputtered spin–valve films

Spin–valve films with the structure Ta/NiFe/FeCo/Cu(18–30 Å)/FeCo/FeMn–70 Å/Ta were deposited using a Veeco ion beam deposition (IBD) system, model IBD-350. The physical properties of these spin–valve films as a function of primary ion beam energy have been studied in a primary ion beam energy range of 600–1500 eV. Xe was used as the working gas. The optimal ion beam energy range for the best spin-valve performance has been found to be around 600 eV. Giant magnetoresistance (GMR) values of ΔR/R∼8% have been measured for the spin–valve films deposited in this energy range. A strong dependence on beam energy of magnetic properties for these spin–valve films has been observed in the energy range from 600 to 1500 eV. ΔR/R for spin–valve films with a Cu layer thickness of 22 Å decreases from 7.5% at 600 eV monotonically to 6.1% at 1500 eV with increasing ion beam energy. Interlayer coupling field increases from 20 Oe at 600 eV to 37 Oe at 1500 eV. Further reduction in the interlayer coupling field to 13 Oe and an increase in ΔR/R to 8% have been achieved by depositing the free layer at 1000 eV and the rest of the layers at 600 eV. These are consistent with the improvement in crystallographic orientation and crystallinity of these spin–valve films.

Effect of ion beam energy on the synthesis of oriented aluminium nitride thin films

Polycrystalline aluminium nitride (A1N) thin films were synthesized by evaporation of aluminium and simultaneous irradiation with nitrogen ions, ion-beam assisted deposition, and the effect of the ion beam energy on the film microstructure was studied. The substrate was single-crystal Si(100), and the substrate temperature was varied from room temperature to 573 K. The kinetic energy of the nitrogen ion beam was varied from 0.05 keV to 0.5 keV. The structure of the A1N thin films was examined by X-ray diffraction (XRD). From the XRD patterns, it is found that (1) the (00•2) plane of hexagonal A1N grows preferentially with an ion beam energy of 0.05 keV (the c -axis oriented structure) independently of the substrate temperature, (2) the intensity of the lines (10•0) and (10•1) becomes stronger with increasing ion beam energy, and (3) the full width at half maximum of the (00•2) diffraction line tends to narrow with decreasing ion beam energy and increasing substrate temperature. The present results show that the ion beam energy plays an important role in the degree of preferred orientation of A1N films and c -axis oriented films can be synthesized at room temperature by controlling the ion beam energy.

Effect of ion beam energy on the synthesis of oriented aluminium nitride thin films

Polycrystalline aluminium nitride (A1N) thin films were synthesized by evaporation of aluminium and simultaneous irradiation with nitrogen ions, ion-beam assisted deposition, and the effect of the ion beam energy on the film microstructure was studied. The substrate was single-crystal Si(100), and the substrate temperature was varied from room temperature to 573 K. The kinetic energy of the nitrogen ion beam was varied from 0.05 keV to 0.5 keV. The structure of the A1N thin films was examined by X-ray diffraction (XRD). From the XRD patterns, it is found that (1) the (00•2) plane of hexagonal A1N grows preferentially with an ion beam energy of 0.05 keV (the c-axis oriented structure) independently of the substrate temperature, (2) the intensity of the lines (10•0) and (10•1) becomes stronger with increasing ion beam energy, and (3) the full width at half maximum of the (00•2) diffraction line tends to narrow with decreasing ion beam energy and increasing substrate temperature. The present results show that the ion beam energy plays an important role in the degree of preferred orientation of A1N films and c-axis oriented films can be synthesized at room temperature by controlling the ion beam energy.

Internal stress in thin films prepared by ion beam and vapor deposition

Abstract The effect of ion beam irradiation on the internal stress in thin films prepared by ion beam and vapor deposition (IVD) was studied. The thin films were prepared by the evaporation of nickel or silicon metals and simultaneous irradiation on Si(100) substrates by argon ion beams. The energies of the argon ions were changed in the range 0.5–10.0 keV, while the transport ratio of vapor atoms to ions was changed from 5 to 15. The internal stresses in the thin films were measured by the displacements of the substrates after deposition, and the results show that the internal stress changed from compressive to tensile with increasing ion beam energy. In addition, the control of the internal stresses in multilayer films prepared by IVD was investigated. It was found that it is possible to control the internal stress in a multilayer film by a suitable combination of the layers.

Differential Reflectance Studies of Structural Changes in GaAs Caused by Ar+ Ion Bombardment

ABSTRACTDifferential reflection (DR) spectrometry has been used to investigate and characterize the effect of sputter damage of GaAs by Ar+ ions. The DR technique provides the photon-induced critical point interband transition energies which are sensitive to the electron and the crystal structure. The spectral dependence of the normalized difference in reflectivity is obtained by periodically scanning monochromatic light across a pair of GaAs samples. In the present case one part has been damaged by Ar+ ions with energies ranging from 500 to 5000 eV. The other half is the undamaged reference. The DR structure caused by interband transitions and designated as E1 and E1 + δ1 were found to shift in energy with increasing ion beam energy or with sputter damage. Two annealing stages were observed, one at 200°C and the other between 400°C and 450°C. They were attributed to different recovering mechanisms of As Frenkel pairs.

Adhesion and structure of c-BN films produced by ion-beam-assisted deposition

Ion beam dynamic mixing was performed to improve the adhesion of cubic boron nitride (c-BN) films prepared by ion-beam-assisted deposition. The interface between the c-BN film and the substrate and the adhesion of prepared films were also studied. Ion beam dynamic mixing was performed on silicon wafers and WC-Co coated with TiN by irradiation by ions with energies of 3 and 7 keV and by simultaneous evaporation of boron. c-BN films were then deposited by irradiation by ions with an energy of 0.5 keV. The structure and the adhesion of the coatings were studied by IR absorption spectroscopy, X-ray diffraction, Auger electron spectroscopy, scratch tests and cutting tests. The adhesion of c-BN films was greatly improved by ion beam dynamic mixing. The critical load determined from scratch tests becomes larger with increasing ion beam energy. No cohesive failures of films prepared by ion beam dynamic mixing with an ion beam energy of 7 keV were observed in cutting tests on carbon steels.

On the influence of ion energy and incidence angle on Auger depth profiles of binary alloys

Sputter behavior of a binary Ag-16%Pd alloy has been investigated by varying the ion energy between 0.5 and 5 keV and the angle of incidence of the ion beam between 0 and 71°. Results are compared to models describing the transient behavior and the steady state surface enrichment. The variation of the relative sputter yield of the pure metals with energy and angle of incidence and matrix effects of the alloy are taken into account. The effective altered layer thickness increases from 1.6 to 3.4 nm with increasing ion beam energy but is independent of angle of incidence. The experimental steady state peak amplitude ratio of Ag/Pd is slightly lower than that calculated based on the sputter yield of the pure metals.