High-temperature Implantation Research Articles

The Effect of High Temperature He+ Implantation on Polycrystalline Tungsten in IR-IECF

High temperature (1,100–1,200°C) implantation impact of helium ions in PC Tungsten as a candidate fusion first wall material was studied in the Iranian Inertial Electrostatic Confinement device (IR-IECF). High energetic (100–120 keV) helium ions were applied to produce fluences up to 5 × 1020 He+/cm2 on the surface of Tungsten. Scanning electron microscopy (SEM) was used to investigate surface morphology changes for various ion fluences. The results showed formation of ‘coral-like’ surface structure and exfoliation and intensive increment in pore formation at high fluence. Microhardness measurements were used to evaluate mechanical properties of implanted tungsten. These investigations revealed that hardness increased with greater He+ dose. The phase formation and structural evolution were studied by X-ray diffractometry method.

Investigation of silver and iodine transport through silicon carbide layers prepared for nuclear fuel element cladding

Transport of silver and iodine through polycrystalline SiC layers produced by PBMR (Pty) Ltd. for cladding of TRISO fuel kernels was investigated using Rutherford backscattering analysis and electron microscopy. Fluences of 2 × 10 16 Ag + cm −2 and 1 × 10 16 I + cm −2 were implanted at room temperature, 350 °C and 600 °C with an energy of 360 keV, producing an atomic density of approximately 1.5% at the projected ranges of about 100 nm. The broadening of the implantation profiles and the loss of diffusors through the front surface during vacuum annealing at temperatures up to 1400 °C was determined. The results for room temperature implantations point to completely different transport mechanisms for silver and iodine in highly disordered silicon carbide. However, similar results are obtained for high temperature implantations, although iodine transport is much stronger influenced by lattice defects than is the case for silver. For both diffusors transport in well annealed samples can be described by Fickian grain boundary diffusion with no abnormal loss through the surface as would be expected from the presence of nano-pores and/or micro-cracks. At 1100 °C diffusion coefficients for silver and iodine are below our detection limit of 10 −21 m 2 s −1, while they increase into the 10 −20 m 2 s −1 range at 1300 °C.

Dynamic annealing versus thermal annealing effects on the formation of hydrogen-induced defects in silicon

The influence of dynamic and thermal annealing on hydrogen platelet formation in silicon have been studied. For cryogenic and room temperature implantations, where dynamic annealing is suppressed, hydrogen platelets form upon subsequent thermal annealing on primarily (100) planes. However, under high temperature implantation (dynamic annealing), a high density hydrogen platelet network consisting of both (111) platelets and (100) platelets is observed. Our findings demonstrate that hydrogen implantation under dynamic annealing conditions leads to a modification of the implantation-induced stress, which eventually guide the nucleation and growth of hydrogen-induced platelets.

Structural and optical properties of 6H–SiC helium-implanted at 600 K

Abstract Single crystals of 6H–SiC were implanted at 600 K with 100 keV He ions to three successively fluences and subsequently annealed at different temperatures ranging from 873 to 1473 K in vacuum. The recovery of lattice damage was investigated by different techniques including Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy and Fourier transform infrared spectroscopy. All three techniques showed that the damage induced by helium ion implantation in the lattice is closely related to the fluence. Rutherford backscattering spectrometry/channeling data on high temperature implantations suggest that for a fluence of 3 × 1016 He+/cm2, extended defects are created by thermal annealing to 1473 K. Apart from a well-known intensity decrease of scattering peaks in Raman spectroscopy it was found that the absorbance peak in Fourier transform infrared spectroscopy due to the stretching vibration of Si–C bond shifted to smaller wave numbers with increasing fluence, shifting back to larger wave numbers with increasing annealing temperature. These phenomena are attributed to different lattice damage behavior induced by the hot implantation process, in which simultaneous recovery was prevailing.

A new high-temperature plasma immersion ion implantation system with electron heating

Abstract The temperature of the substrate has strong influence on the diffusion coefficient of nitrogen ions during plasma immersion ion implantation (PIII) performed in metallic surfaces, which affect the ion implantation profiles and can lead to the formation of thick implanted layers. In order to heat conveniently a large spectrum of metals and metallic alloys in vacuum and in the presence of plasma, as mandatory for efficient PIII, it is necessary to count on a stable heat source, able to provide steady temperatures in the range of 200 °C to more than 1000 °C. This has been accomplished in the current experiment by means of a thermionic cathode composed of a rolled tantalum foil covered with (Ba,Sr,Ca)O. Work-function of this electron source is around 2.1 eV, which is much lower than 4.5 eV of typically used tungsten filament. Metallic samples studied, in this case, are the anode of the discharge itself, being polarized during the heating cycle by positive DC voltages in the 100–800 V range. They are implanted with negative pulses up to 10 kV/300 Hz/40 µs.

Ion beam characterization of Fe-implanted GaN

Abstract Fe ion implantation in GaN has been investigated by means of ion beam analysis techniques. Implantations at an energy of 150 keV and fluences ranging from 2 × 10 15 to 1 × 10 16 cm −2 were done, both at room temperature and at 623 K. Secondary Ions Mass Spectrometry was used to determine the Fe implantation profiles, whereas Rutherford Backscattering in channeling conditions with a 2.2 MeV 4 He + beam allowed us to follow the damage evolution. Particle Induced X-ray Emission in channeling conditions with a 2 MeV H + beam was employed to study the lattice location of Fe atoms after implantation. The results show that a high fraction of Fe-implanted atoms are located in high symmetry sites in low fluence implanted samples, where the damage level is lower, whereas the fraction of randomly located Fe atoms increases by increasing the fluence and the resulting damage. Moreover, dynamical annealing present in high temperature implantation has been shown to favor the incorporation of Fe atoms in high symmetry sites.

Multicomponent nanostructured films for various tribological applications

Abstract Many engineering materials working under severe cutting, stamping, or bearing conditions including humid and corrosive environments, as well as temperature fluctuation require a combination of chemical, mechanical, and tribological properties. For load-bearing metallic implants, the combination of excellent mechanical and tribological properties with biocompatibility and bioactivity is also of great importance. Desired properties can be achieved in hard films based on carbides, borides and nitrides of transition metals by alloying with metallic (Al, Cr, Zr) or nonmetallic (O, P, Si, Ca) elements. The present work demonstrates the potential of self-propagating high-temperature synthesis (SHS), magnetron sputtering (MS), and ion implantation assisted MS of SHS-composite targets to produce multicomponent nanostructured films with enhanced combination of properties. Three groups of recently developed films for mechanical engineering and medicine are considered: hard tribological Ti–(Al, Cr)–(Si, B, C, N) films with enhanced thermal stability, corrosion and oxidation resistance; nanocomposite and multilayered TiCrBN/WSe x films with improved lubrication; and multifunctional bioactive nanostructured (Ti, Ta)–(Ca, Zr)–(C, N, O, Si, P) films (MuBiNaFs).

Surface Electrical Degradation of Helium Implanted Sapphire

Reliable plasma diagnostic systems are key elements for an efficient and safe operation of future fusion reactors. These systems use particular components, such as ceramic insulators, dielectric and optical windows, optical fibres and complete sensor assemblies. These materials, in addition to neutron and gamma radiation, will be subjected to bombardment by low energy ions and neutral particles. Alumina (Al2O3) is one of the insulating candidate materials to be used in diagnostic systems for ITER, where it will play important roles as electrical insulation and in optical components. Possible material damage has been examined by implanting He into sapphire at different temperatures to simulate ion bombardment. The electrical conductivity in the implanted region increases by more than nine orders of magnitude. Such severe surface electrical degradation is due to the loss of oxygen from the implanted surface. The loss of oxygen also reduces the material band gap in the surface region and as a consequence the optical transmission is severely reduced. Implantation temperature plays an important role, where one observes that although electrical degradation is higher for higher temperature implantation, optical degradation is lower. The electrical conductivity in the implanted region increases by more than nine orders of magnitude. Such severe surface electrical degradation is due to the loss of oxygen from the implanted surface. The loss of oxygen also reduces the material band gap in the surface region and as a consequence the optical transmission is severely reduced. Implantation temperature plays an important role, where one observes that although electrical degradation is higher for higher temperature implantation, optical degradation is lower.

High Temperature Implantation: A Solution for n-type Junctions in Strained Silicon

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Ion beam synthesis of SiC by C implantation into SIMOX(1 1 1)

We report the conversion of a 65nm Si(111) overlayer of a SIMOX(111) into 30–45nm SiC by 40keV carbon implantation into it. High temperature implantation (600°C) through a SiO2 cap, 1250°C post-implantation annealing under Ar ambient (with 1% of O2), and etching are the base for the present synthesis. Sequential C implantations (fluence steps of about 5×1016cm−2), followed by 1250°C annealing, has allowed to estimate the minimum C fluence to reach the stoichiometric composition as ∼2.3× 1017cm−2. Rutherford Backscattering Spectrometry was employed to measure layer composition evolution. A two-sublayers structure is observed in the synthesized SiC, being the superficial one richer in Si. Transmission electron microscopy has shown that a single-step implantation up to the same minimum fluence results in better structural quality. For a much higher C fluence (4×1017cm−2), a whole stoichiometric layer is obtained, with reduction of structural quality.

Optical properties revealing annealing behavior of high-temperature He-implantation induced defects in silicon carbide

6H-SiC single crystal specimens were implanted at 600 K with 100 KeV He ions to three successively increasing fluences and subsequently annealed at different temperatures ranging from 600℃ to 1200℃ in vacuum. After the annealing, the samples were investigated by using Raman scattering spectroscopy and photoluminescence spectrometry，respectively. Both of the two methods showed that the damage induced by helium-ion-implantation in the lattice is closely related to the dose. The thermal annealing brings about recovery of the damage，and different levels of damage require different annealing temperature to recover efficiently. It is indicated that different annealing stages involve different mechanisms，corresponding to recombination of point defects，formation of He-vacancy complexes，and nucleation and coarsening of bubbles，respectively. The experimental results indicate that high temperature implantation is an effective way to avoid amorphization of the implanted layer due to damage accumulation. Helium implantation can be used to introduce buried nanoscale cavities as the nucleation site for the buried oxide in a well defined region proposed for an alternative and more economical method of manufacturing SiC-on-Insulator （SiCOI）.

이온주입 제어에 의한 재료특성 개선에 관한 연구

In this study, techniques of ion implantation were used in order to improve the characteristics of metal materials such as the oxidation and wear resistant. In particular it is necessary to develope their oxidation and wear resistant that could be used in severe environmental conditions. There are mainly two elementary technologies including ion implantation and/or thin film coating. Ion implantation method was performed for surface modification. As a result, it was found that some ion implantations methods such as Nb, high-temperature Nb ion implantation and Nb+C combined implantation are somewhat effective for improving the oxidation resistance of TiAl alloy. Furthermore, the fluorine PBII treatment is more effective for improving the oxidation resistance of the TiAl alloy with three-dimensional shapes. The implantation of boron ion into thin film of TiN was also effective for improving the properties of materials like high temperature wear resistance. TiCrN film was applied to the actual seal ring for steam turbines, and it was observed that its sliding property showed a successfully good performance.

Characterization of the donor-acceptor-pair transition in Nitrogen-implanted zinc oxide

Zinc oxide bulk crystals were doped with nitrogen by ion beam implantation. After postimplantation annealing, a luminescent transition appears at 3.230eV. Power-dependent photoluminescence studies and time-resolved measurements at several spectral positions within this band can be described by a model for donor-acceptor-pair (DAP) transitions. By tracing the luminescence in a temperature-dependent study, a connection to phonon replicas could be excluded. Based on these results, this luminescence line could be clearly assigned to a DAP transition. In order to increase the doping efficiency, various approaches are considered and discussed. A slight increase could be obtained by high-temperature implantation without postimplantation annealing.

FTIR and RBS study of ion-beam synthesized buried silicon oxide layers

Single crystal silicon samples were implanted at 140keV by oxygen (16O+) ion beam to fluence levels of 1.0×1017, 2.5×1017 and 5.0×1017cm−2 to synthesize buried silicon oxide insulating layers by SIMOX (separation by implanted oxygen) process at room temperature and at high temperature (325°C). The structure and composition of the ion-beam synthesized buried silicon oxide layers were investigated by Fourier transform infrared (FTIR) and Rutherford backscattering spectroscopy (RBS) techniques. The FTIR spectra of implanted samples reveal absorption in the wavenumber range 1250–750cm−1 corresponding to the stretching vibration of Si–O bonds indicating the formation of silicon oxide. The integrated absorption band intensity is found to increase with increase in the ion fluence. The absorption peak was rather board for 325°C implanted sample. The FTIR studies show that the structures of ion-beam synthesized buried oxide layers are strongly dependent on total ion fluence. The RBS measurements show that the thickness of the buried oxide layer increases with increase in the oxygen fluence. However, the thickness of the top silicon layer was found to decrease with increase in the ion fluence. The total oxygen fluence estimated from the RBS data is found to be in good agreement with the implanted oxygen fluence. The high temperature implantation leads to increase in the concentration of the oxide formation compared to room temperature implantation.

High Temperature Implantation of Aluminum in 4H Silicon Carbide

The influence of the implantation temperature on the surface roughness and the resistivity of aluminum implanted 4H-silicon carbide was determined. A dose of 1.2 ⋅1015cm-2 aluminum ions was implanted at temperatures between room temperature and 1000°C. A decrease of the surface roughness down to an rms-value of 12nm and a decrease in the resistivity down to 0.35Wcm were found with increasing implantation temperature. The influence of the implantation temperature on the resistivity was identified by modeling temperature dependent resistivity data. The results showed an increase in mobility with temperature due to the reduction of compensation centers.

Implantation of He + in candidate fusion first wall materials

The effect of high temperature (700–1200 °C) implantation of helium in candidate fusion first wall materials was studied in the University of Wisconsin Inertial Electrostatic Confinement device. Powder metallurgy tungsten, single crystal tungsten, and a W–25% Re alloy were irradiated with 30–50 keV He + ions. Scanning electron microscopy was used to evaluate changes in surface morphology for various ion fluences at temperature ranges comparable to first wall temperatures. Helium fluences in excess of 1 × 10 18 He +/cm 2 produce extensive pore formation at 1150 °C. These changes will have an impact on the lifetime of thin tungsten coatings on the first walls and divertors of inertial and magnetic confinement fusion reactors.

Microstructural study of dynamically annealed c-Si using MeV N+ ions

Single crystalline Si(100) substrates were irradiated with 1.0MeV N+ ions at elevated temperature to synthesize silicon on insulator materials and to understand the nature of the amorphous region and the defect layer. The RBS-channeling spectra show a sharp amorphous–crystalline interface at a depth of ∼500nm, around half of the mean projected range (Rp). Beyond the Rp a heavily damaged layer has been observed. Micro-Raman spectra show the development of a large amount of stress in the damage free crystalline region. The variation of peak position and FWHM indicates that the surface crystalline quality improves as the implantation temperature increases up to 450°C. The microstructures underneath the surface and interface regions are studied by cross-sectional TEM. We proposed that the ratio of the concentration of vacancies (Nv) and number of nitrogen atoms (NN) coming to rest beyond Rp plays a major role in the formation of damage free near surface region during high temperature implantation.

Multifunctional biocompatible nanostructured coatings for load-bearing implants

To take advantage of the self-propagating high-temperature synthesis (SHS) technique, magnetron sputtering (MS), and ion implantation assisted magnetron sputtering (IIAMS), a new type of biocompatible nanostructured film was developed and studied. Films of Ti–Ca–C–O–(N), Ti–Ca–P–C–O–(N), Ti–Si–Zr–O–(N), and Ti–Zr–C–O–(N) were deposited by DC MS or IIAMS of SHS composite targets TiC 0.5 + CaO, TiC 0.5 + CaO + TiO 2, TiC 0.5 + Ca 10(PO 4) 6(OH) 2, Ti 5Si 3 + ZrO 2, and TiC 0.5 + ZrO 2 in an Ar atmosphere or reactively in a gaseous mixture of Ar + 14% N 2. The films were characterized in terms of their structure, chemical, mechanical, and tribological properties. The biocompatibility of the films was evaluated by both in vitro and in vivo experiments. In vitro studies involved the investigation of adhesion, spreading and proliferation of Rat-1 fibroblasts, MC3T3-E1 osteoblasts, and IAR-2 epithelial cells, morphometric analysis, actin cytoskeleton and focal contacts staining of the cells cultivated on the films. Alkaline phosphatase activity and von Kossa staining of osteoblastic culture were investigated. Three groups of the in vivo investigations were fulfilled. Teflon plates coated with the tested films were inserted subcutaneous in mice and analysis of the population of cells on the surfaces was performed. Implantation studies of Ti rings and Ti rods coated with tested films using rat calvarian and hip defect models were also fulfilled. The results obtained show that Ti-based multicomponent films possess a combination of high hardness and adhesion strength, reduced Young's modulus, low wear and friction, high corrosion resistance with bioactivity, biocompatibility and non-toxicity that makes the films promising candidates as tribological coatings to be used for various medical applications like orthopedic prostheses, materials for connective surgery and dental implants.

Influence of Target Temperature on Cemented Carbides for Ion Implantation

A Cemented Carbide material was implanted with dual nitrogen plus tantalum ions at temperatures of 100 oC and 400 oC and a dose of 8× 1017 ions cm−2. The thickness of the implanted layers increased by about an order of magnitude when the temperature was elevated from 100 oC to 400 oC. Higher surface hardness was also obtained in the high temperature implantation. X-ray diffraction showed the presence of nitrides of tantalum and tungsten in the implanted surface.

Ion beam synthesis of cubic-SiC layer on Si(111) substrate

We have investigated SiC layers produced by ion beam synthesis on Si(111) substrates using different procedures. Bare Si(111) and SiO2∕Si(111) structures were implanted with carbon at 40keV up to a fluence of 4×1017cm−2 at a temperature of 600°C. Postimplantation annealing was carried out at 1250°C for 2h in pure O2 or Ar (with 1% of O2). A SiC layer was synthesized for all the procedures involving annealing under Ar. However, for the samples annealed under pure O2 flux, only that employing implantation into the bare Si(111) resulted in SiC synthesis. Rutherford backscattering spectrometry shows that, after annealing, the stoichiometric composition is obtained. Transmission electron microscopy measurements demonstrate the synthesis of cubic-SiC layers that are completely epitaxial to the Si(111) substrate. However, there is a high density of nanometric twins, stacking faults, and also narrow amorphous inclusions of laminar shape between the crystalline regions. The procedure based on high temperature implantation through a SiO2 cap, etching the cap off, 1250°C postimplantation annealing under Ar ambient (with 1% of O2), and final etching has shown advantages from the point of view of surface flatness and increased layer thickness, keeping the same layer epitaxy and accurate composition.