Magnetic behavior of Ni+ implanted silica

Ni⁺ has been implanted in amorphous silica layers and silica glasses at two dose levels (10¹⁶ and 10¹⁷ Ni⁺ cm⁻²) and two different energies (30 and 160 keV). Superparamagnetic and ferromagnetic behaviors were observed with a SQUID magnetometer at RT and 5 K, respectively. Using Langevin’s theory, the size of the metallic nanoparticles were deduced to ranges between 2 and 6.5 nm in good agreement of HRTEM observations. The E′ type center and the neutral oxygen vacancy (NOV) defects were observed by UV–Vis absorption. Finally, in samples annealed at 600°C under Ar or Ar + H₂ atmospheres two different phenomena were observed: the reduction of Ni²⁺ to Ni⁰ and the elimination of defects introduced by implantation.     

Defects in carbon and oxygen implanted p-type silicon

Both oxygen and carbon ion implantation are frequently used to form either insulating buried SiO₂ or SiC layer for various purposes. This creates a renewal of the interest in defects produced during such implantation processes. In the present paper we report on deep level transient spectroscopy studies of defect states occurring in boron-doped p-type silicon after high dose C⁺ and CO⁺ ion implantation and subsequent thermal annealing. It is shown that the predominant defect created during the implantation is in both cases related to silicon selfinterstitial clusters, which upon annealing at higher temperatures evolve to extended structural defects.     

Surface bioactivity of plasma implanted silicon and amorphous carbon

Plasma immersion ion implantation and deposition (PⅢ&D) has been shown to be an effective technique to enhance the surface bioactivity of materials. In this paper, recent progress made in our laboratory on plasma surface modification single-crystal silicon and amorphous carbon is reviewed. Silicon is the most important material in the integrated circuit industry but its surface biocompatibility has not been investigated in details. We have recently performed hydrogen PⅢ into silicon and observed the biomimetic growth of apatite on its surface in simulated body fluid. Diamond-like carbon (DLC) is widely used in the industry due to its excellent mechanical properties and chemical inertness. The use of this material in biomedical engineering has also attracted much attention. It has been observed in our laboratory that doping DLC with nitrogen by means of PⅢ can improve the surface blood compatibility. The properties as well as in vitro biological test results will be discussed in this article.     

Surface bioactivity of plasma implanted silicon and amorphous carbon

1 Introduction tors.[10,11] In addition, it has been shown that the criti- cal concentration of ionic products dissolved from the Since the discovery of SiO2-based bioglass in bioactive glass composed of soluble silicon and cal-1969,[1] possible applications of silicon-containing cium ions can enhance osteogenesis th…     

碳团簇Cnn+(n=15)注入NaCl晶体的模型

６００ｋｅＶ的荷能碳和簇离子Ｃ＾＋ｎ（ｎ＝１－５）注入到ＮａＣｌ单晶,当入射粒子的速度ｖ大于玻尔速度ｖ０（＝３／１３７）时,能量转移主要是由入射粒子与靶原子的核外电子碰撞造成的。假定团簇中各原子的能量岐离大于它们的结合能时,团簇状态已经结束,各原子成为独立的粒子。     

Temperature behavior of damage in sapphire implanted with light ions

In this study, we compare and discuss the defect behavior of sapphire single crystals implanted with different fluences (1 × 10¹⁶–1 × 10¹⁷ cm^?2) of carbon and nitrogen with 150 keV. The implantation temperatures were RT, 500 °C and 1000 °C to study the influence of temperature on the defect structures. For all the ions the Rutherford backscattering-channeling (RBS-C) results indicate a surface region with low residual disorder in the Al-sublattice. Near the end of range the channeled spectrum almost reaches the random indicating a high damage level for fluences of 1 × 10¹⁷ cm^?2. The transmission electron microscopy (TEM) photographs show a layered contrast feature for the C implanted sample where a buried amorphous region is present. For the N implanted sample the Electron Energy Loss Spectroscopy (EELS) elemental mapping give evidence for the presence of a buried damage layer decorated with bubbles. Samples implanted at high temperatures (500 °C and 1000 °C) show a strong contrast fluctuation indicating a defective crystalline structure of sapphire.     

Surface decomposition and annealing behavior of GaN implanted with Eu

Investigations on surface decomposition of GaN implanted with low energy (80keV) Eu ion to a low dose (1×1014cm-2), and its annealing behavior under high temperature (1050℃) in N2 are performed. The as-grown, as-implanted and annealed GaN films are characterized by proton elastic scattering (PES), Rutherford backscattering spectrometry (RBS), photoluminescence (PL) and atomic force microscopy (AFM). The results show that Eu ion implantation induces radiation defects and decomposition of GaN. The GaN surface decomposition is more serious during high temperature annealing. The atomic ratio of N in as-grown, as-implanted and annealed GaN film is 47 at.%, 44 at.% and 40 at.%, respectively. As a result, a rough Ga-rich layer is formed at the surface, though the lattice defects are partly removed after high temperature annealing.     

The annealing behavior of Cu nanoparticles in Ar-ion implanted spinel

Magnesium aluminate spinel crystals (MgAl₂O₄ (1 1 0)) deposited with 30 nm Cu film on surface were implanted with 110 keV Ar-ions to a fluence of 1.0 × 10¹⁷ ions/cm² at 350 °C, and then annealed in vacuum condition at the temperature of 500, 600, 700, 800 and 900 °C for 1 h, respectively. Ultraviolet-visible spectrometry (UV-VIS), scanning electron microscopy (SEM), Rutherford backscattering (RBS) and transmission electron microscopy (TEM) were adopted to analyze the specimens. After implantation, the appearance of surface plasmon resonance (SPR) absorbance peak in the UV-VIS spectrum indicated the formation of Cu nanoparticles, and the TEM results for 500 °C also confirmed the formation of Cu nanoparticles at near-surface region. In annealing process, The SPR absorbance intensity increased at 500 and 700 °C, decreased with a blue shift of the peak position at 600 and 800 °C, and the peak disappeared at 900 °C. The SPR absorbance intensity evolution with temperature was discussed combined with other measurement results (RBS, SEM and TEM).     

Electrical and photoluminescence properties of carbon implanted ZnO bulk single crystals

Carbon-ions, which are expected as an amphoteric impurity, are implanted into ZnO bulk single crystals with a fluence of 1.5 × 10¹⁵ cm^?2. The carbon-ion implanted ZnO shows the n-type conductivity and the resistivity varies from 6 × 10⁴ Ω cm (for unimplanted samples) to 3 × 10^?2 Ω cm (for 800 °C-annealed ones). The Rutherford backscattering (RBS) studies show the existence of the displaced zinc atoms. In photoluminescence (PL) measurements, the broad emission at 2.34 eV observed in un-implanted and as-implanted samples is related to oxygen vacancy and zinc interstitial. After annealing, the weak PL-emission related to carbon donor is observed at 3.06 eV, indicating that the donor level lies at ～310 meV below the conduction band. The carbon-ion implanted ZnO layer with the low resistivity achieved in the present study suggests the possibility of transparent conductive oxide.     

A molecular dynamics study of the clustering of implanted potassium in multiwalled carbon nanotubes

We have studied the low energy irradiation of carbon nanotubes (CNT) with K ions using classical molecular dynamics simulations with analytical potentials. The studied CNTs had diameters of about 0.5–1.2 nm and single or multiple walls. The average penetration depth and probabilities to introduce an impurity atom into CNT were studied with simulations on irradiating the CNT with single K ion. The number of potassium clusters, their average sizes and the damage produced into the CNT due to the irradiation were studied using multiple K ion irradiations. We found that the K ions are mobile in CNTs right after the implantation event and that they cluster together. For CNTs with 1–3 coaxial tubes, the highest ratio of K atoms in clusters per total number of K ions was obtained by using an irradiation energy of about 100 eV. Also the least damage per K ion was found to be produced into the CNT with this energy when those energies high enough for the ion to penetrate the outermost wall of the CNT were considered.     

A broad chemical and structural characterization of the damaged region of carbon implanted alumina

As candidate materials for future thermonuclear fusion reactors, isolating ceramics will be submitted to high energy gamma and neutron radiation fluxes together with an intense particle flux. Amorphization cannot be tolerated in ceramics for fusion applications, due to the associated volume change and the deterioration of mechanical properties. Therefore, a comprehensive study was carried out to examine the effects of carbon beam irradiation on polycrystalline aluminium oxide (Al₂O₃), a ceramic component of some diagnostic and plasma heating systems. Complementary techniques have allowed a complete chemical and structural surface analysis of the implanted alumina. Implantation with 75 keV, mono-energetic carbon ions at doses of 1 × 10¹⁷ and 5 × 10¹⁷ ions/cm² was performed on polished and thermally treated ceramic discs. The alumina targets were kept below 120 °C. The structural modifications induced during ion irradiation were studied by the GXRD and TEM techniques. Under these conditions, alumina is readily amorphized by carbon ions, the thickness of the ion-beam induced disordered area increasing with the ion dose. Matrix elements and ion implanted profiles were followed as a function of depth by using ToF-SIMS, indicating the maximum concentration of implanted ions to be in the deeper half of the amorphous region. Ion distribution and chemical modifications caused in the Al₂O₃ substrate by carbon irradiation were corroborated with XPS. The amount of oxygen in the vicinity of the implanted alumina surface was reduced, suggesting that this element was selectively sputtered during carbon irradiation. The intensity of those peaks referring to Al–O bonds diminishes, while contributions of reduced aluminium and metal carbides are found at the maximum of the carbon distribution. TEM observations on low temperature thermally annealed specimens indicate partial recovery of the initial crystalline structure.     

Effects of environment on annealing behavior of In+ implanted c-axis sapphire

Single crystal samples of 〈0001〉α-Al₂O₃ were implanted with 360 keV indium ions of doses of 1 × 10¹⁶ and 3 × 10¹⁶ ions/cm², at room temperature (RT). The implanted samples were annealed isothermally in air or in flowing high purity argon ambient at 900°C for 2 or 12 h. The damage and thermal annealing were evaluated using Rutherford Backscattering Spectrometry and Channeling (RBS-C) and X-ray Diffraction (XRD). Amorphization of sapphire was not observed, despite damage energy densities up to 105 dpa (displacements per atom obtained from TRIM code calculation) for the Al sublattice, which indicated that self-annealing was severe during In ion implantation of sapphire at RT. RBS-C measurement revealed differences in the annealing characteristics of the implanted indium ions that depended on the annealing environment. The XRD spectrum indicated the presence of the In₂O₃ phase in the subsurface region of the sample after annealing in air.     

Graphitization of free carbon precipitating through the reaction of UC or UC2 with N2

It has been found by X-ray diffraction that free carbon produced from reaction of UC or UC₂ with nitrogen gas is not graphite but an amorphous carbon. The degree of graphitization increases with increasing temperature and with decreasing pressure of nitrogen gas. Thermodynamic treatment of these amorphous carbons is discussed in terms of the degree of graphitization. The free energies of the amorphous carbons are calculated to be higher by about 500 cal/mol than that of graphite. Furthermore, the influence of the crystal structure of UC or UC₂ on the degree of graphitization is considered qualitatively.     

The range distribution and annealing behavior of Er ions implanted in silicon-on-insulator

The range distribution for energetic 400 keV Er ions implanted in silicon-on-insulator (SOI) at room temperature were measured by means of Rutherford backscattering followed by spectrum analysis. The damage distribution and annealing behavior of implanted Er ions in SOI at the energy of 400 keV with dose of 5 × 10¹⁵ cm⁻² were obtained by Rutherford backscattering technique. It has been found that the damage around the SOI surface had been almost removed after annealed in nitrogen atmosphere at 900 °C, and a lot of Er atoms segregate to the surface of sample with the recrystallization of surface Si of SOI sample after annealing at 900 °C.     

Visible photoluminescence of SiO2 implanted with carbon and silicon

The structures formed after sequential implantation of silicon plus carbon in amorphous SiO₂ and annealing presented strong photoluminescence bands in the deep red (1.4–1.6 eV) and green (2.0–2.2 eV) regions of the visible spectrum. The energy and intensity of the bands depended strongly on the temperature and duration of annealing. Different behaviours with post-processing were encountered for the red and green bands, including deexcitation kinetics and structural origin. The FTIR, Raman and HRTEM measurements showed that silicon crystallites were reponsible for the red emitting band while carbon aggregates were probably the origin of the green one.     

Depth profiling a near surface carbon contaminant in implanted first wall materials

Current attempts to generate stable plasmas in CTR devices are encountering severe material problems. Plasma species, interacting with the surface of the containment vessel, can desorb surface species which can contaminate the plasma or, interacting with surface impurities, can change the properties of the near surface region. Although methods to minimize these synergistic effects have been suggested, there exists only minimal information related to the fundamental surface and near surface (< 100 Å) processes involved. One process of interest, the interaction of energetic plasma species with adsorbed hydrocarbon contaminants has been examined using Imaging, Field-Desorption Mass Spectrometry. Angstrom resolved depth profiles of a carbon contaminant produced by ion-beam decomposition of an adsorbed surface hydrocarbon layer have been measured for tungsten, molybdenum and stainless steel specimens. The observed, 30 Angstrom penetration of carbon into the near surface region suggests that conventional first-wall cleaning techniques may be ineffective in completely removing this impurity.     

Effect of residual carbon on the sintering behavior of MOX pellets

Sintering behavior of MOX compacts containing different amounts of carbon (290–1735 ppm) was investigated at temperatures from 1073 to 2023 K to study the effect of residual carbon. Specimen shrinkages were measured with a non-contact type optical dilatometer during heating. The compact shrinkage at temperatures from 1273 to 1523 K was about six times larger in the two specimens with high residual carbon content than in the two with low content. This behavior could be understood by considering that shrinkage of the former specimens was enhanced in this temperature range by the decrease of O/M ratio due to the evolution of CO gas and consequently the significant increase of the metal ion inter-diffusion coefficient. In the specimens with low residual carbon content, the amount of CO gas evolution was too small to affect the inter-diffusion coefficient. This difference in shrinkage between the two kinds of specimens was also discussed from a theoretical model applied to the initial sintering stage of ceramics.     

Thermal annealing behavior of hydrogen and surface topography of H2+ ion implanted tungsten

Tungsten (W) has been proposed as a plasma-facing material in fusion reactors due to its outstanding properties. Degradation of the material properties is expected to occur as a result of hydrogen (H) isotope permeation and trapping in W. In this study, two polycrystalline W plates were implanted with 80 keV H₂⁺ ions to a fluence of 2 × 10²¹ H⁺/m² at room temperature (RT). Time-of-flight secondary ion mass spectrometry (ToF-SIMS), focused ion beam (FIB), and scanning electron microscopy (SEM) were used for sample characterization. The SIMS data shows that H atoms are distributed well beyond the ion projected range. Isochronal annealing appears to suggest two H release stages that might be associated with the reported activation energies. H release at RT was observed between days 10 and 70 following ion implantation, and the level was maintained over the next 60 days. In addition, FIB/SEM results exhibit H₂ blister formation near the surface of the as-implanted W. The blister distribution remains unchanged after thermal annealing up to 600 ?C.     

Sulfurization behavior of thorium dioxide with carbon disulfide

A novel reprocessing process based on sulfide chemistry has been proposed for the recovery of nuclear materials from spent fuel. To apply the sulfide process in the thorium fuel cycle, the sulfurization behavior of thorium dioxide (ThO₂) with CS₂ was examined as a basic study. When thorium dioxide powder reacted with a mixture gas of Ar and CS₂ at different temperatures in a quartz reaction tube, the phases after the reaction were identified by the X-ray diffraction method. At temperatures lower than 673 K, ThO₂ was found to be stable because the lattice parameter of the ThO₂ phases does not change with increasing sulfurization temperatures. However, the weight gradually increased, suggesting that a small amount of sulfur was trapped in the lattice from the sulfurization. The formation of the intermediate phase ThOS was observed at 973 K. At 1073 K, both the ThOS and ThS₂ phases were observed. Finally, a single phase of ThS₂ was obtained at temperatures higher than 1173 K. The obtained results were compared with the thermodynamic consideration by using the potential diagram of the Th-S₂-O₂ system and the experimental results were in good agreement with the thermodynamic considerations.