Ion-beam irradiation effects on reactively sputtered CrN thin films

The present study deals with CrN/Si bilayers irradiated at room temperature (RT) with 120 keV Ar ions. The CrN layers were deposited by d.c. reactive sputtering on Si(1 0 0) wafers, at different nitrogen partial pressures (2 × 10⁻⁴, 3.5 × 10⁻⁴ and 5 × 10⁻⁴ mbar), to a total thickness of 240-280 nm. The substrates were held at room temperature (RT) or 150 °C during deposition. After deposition the CrN/Si bilayers were irradiated up to fluences of 1 × 10¹⁵ and 1 × 10¹⁶ ions/cm². Structural characterization was performed with Rutherford backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM) and grazing angle X-ray diffraction (XRD). For the highest nitrogen pressure (5 × 10⁻⁴ mbar) a pure stoichiometric CrN phase was achieved. The results showed that Ar ion irradiation resulted in the variation of the lattice constants, micro-strain and mean grain size of the CrN layers. The observed microstructural changes are due to the formation of the high density damage region in the CrN thin film structure.     

Polyimide-based scintillating thin films

The production procedure and the scintillation characteristics of thin polyimide films containing rhodamine B are reported. Fluorinated polyimide has been chosen as host matrix for its well known radiation hardness, in order to improve the lifetime of detector systems based on plastic thin film scintillators, 6FDA (4,4'-hertafluoroisopropylidene diphthalic anhydride) and DAB (diaminobenzophenone) have been used as polyimide precursor monomers. The samples have been cured in air at temperatures ranging from 80°C up to 250°C. The scintillation spectra have been collected by irradiating the samples with a 5.478 MeV alpha particle source and their shape and intensity have been investigated as a function of dopant concentration and curing temperature     

Ferroelectricity in Li-implanted ZnO thin films

ZnO:Li thin films were prepared by implantation of ZnO with a Li ion fluence 5 × 10¹⁶ ions/cm² at implantation energies of 50, 100, 200 keV. Ferroelectric characterization of the implanted samples revealed a clear hysteresis in the polarization-field curves. The origin of the ferroelectricity can be attributed to an off-center dipole caused by the large difference in ionic radii between the host Zn (0.74 Å) and the dopant Li (0.60 Å). ZnO:Li films which were implanted at 200 keV and annealed at a temperature of 700 ^°C exhibited a well-defined polarization hysteresis loop, with a remanent polarization of 0.8 μC/cm² and coercive field of 8.2 kV/cm, at room temperature. The dielectric phase transition was observed in the temperature range from 340 to 360 K. It is concluded that this novel ferroelectric phase transition in ZnO:Li results from the small structural distortion induced along the c-axis.     

Decay Station at Beijing Radioactive Ion-beam Facility

正The Beijing Radioactive Ion-beam Facility(BRIF)is a national large-scale scientific infrastructure of several hundreds of million budgets.The facility is commissioned as the national first RIB facility based on the isotope separator on line(ISOL)technique.BRIF is comprised of a highintensity proton cyclotron,ion source,ISOL,and the I-13 tandem as the post accelerator.     

Highly charged ion interactions with thin insulating films

The electrical conductance of magnetic tunnel junction (MTJ) devices whose ultra-thin aluminum oxide tunnel barriers were irradiated by highly charged ions (HCIs) increases linearly with the fluence of HCIs, while retaining a current-voltage relationship indicative of a tunnel junction. The slope of the MTJ conductance σ_c as a function of fluence varies with different tunnel barrier thicknesses d, levels of oxidation (stoichiometry) and charge state q. Since the MTJ conductance after HCI irradiation is due to tunneling, the increased conductance can result from thinning the barrier, reducing the effective tunnel barrier height φ, or both. Measurements of the current-voltage profile provide sufficient degrees of freedom to substantially constrain d and φ provided the reduction of the barrier remains within the assumptions of the commonly used WKB (Wentzel-Kramers-Brillouin) tunneling formalism. For the Xe³²⁺ ions discussed here the perturbation of the tunnel barrier is much weaker than in our previously reported measurements of Xe⁴⁴⁺ and application of WKB is still reasonable. This analysis reveals a trend of decreasing d while φ changes little.     

Sub-micron calibration for ion beam milling of thin films

Multiple beam interferometry and Rutherford backscattering spectrometry are used to extend the calibration of the amount of material removed by an ion miller to 2 nm.     

Ion beam analysis of rare earth nitride thin films

We report compositional measurements on highly disordered GdN, DyN, ErN and SmN thin films, grown using ion-assisted deposition and capped with GaN AlN and Al, grown using the same technique. Ion beam analysis technique of RBS, PIXE and nuclear reaction analysis (NRA) were used to determine the composition of the capped films ex situ, and show that GaN and AlN protects the GdN, DyN and SmN films from oxidation over a timescale of at least a few days. NRA depth profiles indicate that oxygen is incorporated into the films during deposition and is located at the GaN/GdN interface. The ion beam analysis measurements showed that stoichiometric ratios can be obtained and oxygen impurities are significantly reduced by varying the film deposition parameters. The successful protection of the rare earth (RE) nitride films from oxidation allows for a reliable analysis of the RE films in the as-deposited state.     

氧化钨薄膜变色机理研究

利用慢正电子柬流技术和X射线光电子能谱研究了热致变色和电致变色三氧化钨(WO3)薄膜中W离子在膜内和表面的分布。结合其变色性能,讨论了热致变色和电致变色之间的相关性。     

Angular dispersion of protons passing through thin metallic films

The angular distributions of protons after traversing thin polycrystalline Al targets (15 nm) with an incident energy of 10 keV have been measured and an analysis of the targets by means of transmission electron microscopy (TEM) techniques has been made. The separate influence of the different crystal characteristics and defects has been evaluated by numerical simulation considering the interaction of the ion with all the nearest neighboring atoms simultaneously. In the analysis we included the evaluation of the effects of lattice vibrations, oxide layers and foil roughness on the angular distributions. Previous experimental data in monocrystalline and polycrystalline Au targets has also been analyzed. For a consistency check a comparison with the results of the MARLOWE code for the simpler case of proton channeling in 1 0 0 Al has been performed. As in the case of Au, the present results indicate that the experiments can be explained in terms of a modified Moliere potential, and confirm the critical influence of crystal characteristics, in this case the amorphous oxide layer on the surface and the thermal vibration of the lattice atoms.     

Elemental analysis of light constituents in thin plastic films

Experiments with 1-3 MeV ⁴He beams and 2.2-3.2 MeV proton beams have been performed in order to develop a precise and highly sensitive method for the detection and analysis of light elements in threat or drug materials using simultaneously the RBS and ERDA techniques. Commercially available plastic films have been used as samples. The 1 MeV ⁴He beam has been found to be inadequate owing to the rapid destruction of the targets. Best results have been obtained using proton beams with energies higher than 3 MeV. For 3.2 MeV proton beams, ERDA has been used for the analysis of the hydrogen constituent.     

Sputtering of thin benzene films by large noble gas clusters

Molecular dynamics computer simulations have been employed to investigate the sputtering process of a benzene (C₆H₆) monolayer deposited on Ag{1 1 1} induced by an impact of slow clusters composed of large number of noble gas atoms. The sputtering yield, surface modifications, and the kinetic energy distributions of ejected species have been analyzed as a function of the cluster size and the binding energy of benzene to the Ag substrate. It is shown that high- and low-energy components can be identified in the kinetic energy distributions of ejected molecules. The mechanistic analysis of calculated trajectories reveals that high-energy molecules are emitted by direct interaction with projectile atoms that are backreflected from the metal substrate. Most of the molecules are ejected by this process. Low-energy molecules are predominantly emitted by a recovering action of the substrate deformed by the impact of a massive cluster. The increase of the binding energy leads to attenuation of both high- and low-energy ejection channels. However, low-energy ejection is particularly sensitive to the variation of this parameter. The area of the molecular overlayer sputtered by the projectile impact is large and increases with the cluster size and the kinetic energy of the projectile. Also the size and the shape of this area are sensitive to the changes of the binding energy. The radius of the sputtered region decreases, and its shape changes from almost circular to a ring-like zone when the binding energy is increased. Some predictions about the perspectives of the application of large clusters in the organic secondary ion mass spectrometry are discussed.     

CdTe detector use for PIXE characterization of TbCoFe thin films

Peltier cooled CdTe detectors have good efficiency beyond the range of energies normally covered by Si(Li) detectors, the most common detectors in PIXE applications. An important advantage of CdTe detectors is the possibility of studying K X-rays lines instead the L X-rays lines in various cases since CdTe detectors present an energy efficiency plateau reaching 70 keV or more. The ITN CdTe useful energy range starts at K-K_α (3.312 keV) and goes up to 120 keV, just above the energy of the lowest γ-ray of the ¹⁹F(p, p’γ)¹⁹F reaction. In the new ITN HRHE-PIXE line, a CdTe detector is associated to a POLARIS microcalorimeter X-ray detector built by Vericold Technologies GmbH (an Oxford Instruments Group Company). The ITN POLARIS has a resolution of 15 eV at 1.486 keV (Al-K_α) and 24 eV at 10.550 keV (Pb-L_α1). In the present work, a TbCoFe thin film deposited on a Si substrate was analysed at the HRHE-PIXE system. The good efficiency of the CdTe detector at 45 keV (Tb-K_α), and the excellent resolution of POLARIS microcalorimeter at 6.403 keV (Fe-K_α), are presented and the new possibilities open to the IBA analysis of systems with traditionally overlapping X-rays and near mass elements are discussed.     

Growth and surface morphology of ion-beam sputtered Ti-Ni thin films

Titanium-nickel thin films have been deposited on float glass substrates by ion beam sputtering in 100% pure argon atmosphere. Sputtering is predominant at energy region of incident ions, 1000 eV to 100 keV. The as-deposited films were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). In this paper we attempted to study the surface morphology and elemental composition through AFM and XPS, respectively. Core level as well as valence band spectra of ion-beam sputtered Ti-Ni thin films at various Ar gas rates (5, 7 and 12 sccm) show that the thin film deposited at 3 sccm possess two distinct peaks at binding energies 458.55 eV and 464.36 eV mainly due to TiO₂. Upon increasing Ar rate oxidation of Ti-Ni is reduced and the Ti-2p peaks begin approaching those of pure elemental Ti. Here Ti-2p peaks are observed at binding energy positions of 454.7 eV and 460.5 eV. AFM results show that the average grain size and roughness decrease, upon increasing Ar gas rate, from 2.90 μm to 0.096 μm and from 16.285 nm to 1.169 nm, respectively.     

Nanoindentation characterization of ErT2 thin films

The properties of ErT₂ films change as the tritium decays into ³He, which has important implications for long-term film stability in applications such as neutron generators. Ultra-low load nanoindentation, analyzed using finite-element modeling to separate the nanomechanical properties of 500 nm ErT₂ layers from those of the underlying substrates, has been used to examine the films as they age. The ³He bubbles which form as the film ages act as barriers to dislocation movement, hardening the material, but not dramatically affecting the elastic properties. By modeling the layer as an isotropic, elastic-plastic solid with the Mises yield criterion, the nanoindentation data is shown to correspond to an increase of nearly 2× in strength after aging for over a year.     

Ion-beam induced compositional changes in alloys at elevated temperatures

Near-surface compositional changes in alloys during ion bombardment have been studied theoretically. The scheme employed ensures pressure relaxation of the target, and the effects of preferential sputtering, collisional mixing, radiation-enhanced diffusion, and Gibbsian and radiation-induced segregation are allowed for. High-fluence composition profiles were determined directly from a nonlinear integro-differential equation by means of an efficient iteration procedure developed recently. The dependence of the composition profile on input parameters such as target temperature and defect mobility was examined for Ni---Cu and Ni---Pd alloys.     

Progress Report of Beijing Radioactive Ion-beam Facility(BRIF)

正2016 is the year of the tandem accelerator upgrade project construction acceptance.In this year,the Beijing Radioactive Ion-beam Facility(BRIF)successfully completed the tasks.1 BRIF project through acceptance In February 2016,BRIF project occupational health and completion of financial accounts audit reports were approved,and the completion report