High temperature silver ion implantation into glass

Soda-lime-silicate glass has been implanted with 55 keV Ag⁺ ions at five different temperatures: room temperature, 100, 225, 350 and 600°C. Rutherford backscattering spectroscopy was used to provide depth profiles for the implants. All samples show a low retention of silver and this varies with temperature. In the room temperature and 100°C implants the silver diffuses to, and is lost from the surface. This also occurs in the higher temperature implants, but in these cases there is a significant amount of inward diffusion by the silver. This diffusion extends to at least 500 nm: greatly in excess of the predicted range for a standard implant. Optical measurements on the samples show that those with the inward diffusion have formed an enhanced-index waveguide.     

High temperature high dose C ion implantation in epitaxial SiGe

Si_{1 − x}Ge_x epitaxial layers fully strained (x = 0.27) and relaxed (x = 0.55) have been implanted with C ions at 500°C. Implantation energy and doses were selected to obtain the C peak in the central region of the SiGe layer, with a concentration similar to the Ge content. The implanted layers have been analyzed by Raman scattering, X-ray diffraction, transmission electron microscopy and secondary ion mass spectroscopy. The data obtained show the direct synthesis of β-SiC precipitates aligned in relation to the SiGe lattice after the implantation, as well as a Ge enrichment and stress relaxation of the SiGe lattice. For the relaxed layer a significant Ge redistribution from the implanted region is observed.     

High temperature surface effects of He implantation in ICF fusion first wall materials

The first wall armor of the inertial confinement fusion reactor chambers must withstand high temperatures and significant radiation damage from target debris and neutrons. The resilience of multiple materials to one component of the target debris has been investigated using energetic (20-40 keV) helium ions generated in the inertial electrostatic confinement device at the University of Wisconsin. The materials studied include: single-crystalline, and polycrystalline tungsten, tungsten-coated tantalum-carbide ‘foams’, tungsten-rhenium alloy, silicon carbide, carbon-carbon velvet, and tungsten-coated carbon-carbon velvet. Steady-state irradiation temperatures ranged from 750 to 1250 °C with helium fluences between 5 × 10¹⁷ and 1 × 10²⁰ He⁺/cm². The crystalline, rhenium alloyed, carbide foam, and powder metallurgical tungsten specimens each experienced extensive pore formation after He⁺ irradiation. Flaking and pore formation occurred on silicon carbide samples. Individual fibers of carbon-carbon velvet specimens sustained erosion and corrugation, in addition to the roughening and rupturing of tungsten coatings after helium ion implantation.     

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

We report the conversion of a 65 nm Si(1 1 1) overlayer of a SIMOX(1 1 1) into 30–45 nm SiC by 40 keV 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 × 10¹⁶ cm^?2), followed by 1250 °C annealing, has allowed to estimate the minimum C fluence to reach the stoichiometric composition as ～2.3 ×  10¹⁷ cm^?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 × 10¹⁷ cm^?2), a whole stoichiometric layer is obtained, with reduction of structural quality.     

High fluence nitrogen implantation in Al/Ti multilayers

We have studied the effects of high fluence nitrogen ion implantation on the structural changes in Al/Ti multilayers, with the aim of achieving multilayered metal-nitrides. The starting structures consisted of 10 alternate sputter-deposited Al and Ti films, with a total thickness of 270 nm, on (1 0 0) Si substrates. They were implanted with 200 keV , to 1 × 10¹⁷ and 2 × 10¹⁷ at/cm², the projected range being around half-depth of the multilayers. Structural characterization was performed by Rutherford backscattering, Auger electron spectroscopy and transmission electron microscopy. It was found that ion implantation to the higher fluence induces a full intermixing of Al/Ti layers, resulting in a multilayered structure with different content of Al, Ti and N. The applied method can be interesting for preparation of graded (Al,Ti)N multilayers, with a controlled content of nitrogen and a controlled level of Al-Ti intermixing within the structures.     

High dose uranium ion implantation into silicon

Implantation of uranium ions into silicon to a dose of 6 × 10¹⁶ atoms/cm², with a maximum concentration of 6 × 10²¹ atoms/cm³, has been carried out at an ion mean energy of 157 keV. The implanted uranium content was measured by Rutherford backscattering and confirmed by a measurement of the alpha-particle activity of the buried uranium layer. The range and straggling of the uranium implant, and sputtering of the silicon target by uranium, were measured and are compared with theoretical estimates.     

高剂量N^＋注入碳膜形成氮化碳CNx的研究

研究了利用高剂量的Ｎ＾＋注入碳膜形成氮化碳ＣＮｘ的可能性，对这种新材料进行了城叶变换红外吸收光谱、Ｘ射线光电子能说、Ｘ射线衍射和薄膜的维氏显微硬度等测量。结果表明，在１００ｋｅＶ高剂量Ｎ＾＋注入碳膜过程中形成了含有碳氮共价键成分的ＣＮｘ化合物。     

High temperature reactor development in China

Since the late 1970'-s the research and development program on the high temperature gas-cooled reactor (HTR) has been carried out in China. The 10 MW High Temperature Gas-cooled Reactor-Test Module (HTR-10) reached first criticality in 2000 and was put into full power operation in 2003. Six safety demonstration tests were done on the HTR-10. The project of the HTR-10 with a gas turbine cycle is underway. The project of the HTR demonstration plant with a power of around 150 MWe (HTR-PM) is planned. In this paper the HTR development in China is briefly described.     

High temperature component design

High temperature component design requires the consideration of constructive aspects prior to design and dimensioning work. In the high temperature range of more than 800°C special importance is attached to the failure modes “creep fatigue”, “ratcheting” and “creep buckling”. Comprehensive examinations of existing design rules considering these failure modes with regard to possible applicability for HTR-conditions have been completed. Corresponding calculations have pointed out that there is a promising potential for safe component design even for extreme temperature load conditions. These results have additionally confirmed that available elastic methods often cannot be used and would lead to very conservative approximations. Thus the improvement of simplified verification methods as well as the improvement of relevant constitutive equations is required in view of further development work in the field of high temperature component design.     

Medium temperature carbon dioxide gas turbine reactor

A carbon dioxide (CO₂) gas turbine reactor with a partial pre-cooling cycle attains comparable cycle efficiencies of 45.8% at medium temperature of 650 °C and pressure of 7 MPa with a typical helium (He) gas turbine reactor of GT-MHR (47.7%) at high temperature of 850 °C. This higher efficiency is ascribed to: reduced compression work around the critical point of CO₂; and consideration of variation in CO₂ specific heat at constant pressure, C_p, with pressure and temperature into cycle configuration. Lowering temperature to 650 °C provides flexibility in choosing materials and eases maintenance through the lower diffusion leak rate of fission products from coated particle fuel by about two orders of magnitude. At medium temperature of 650 °C, less expensive corrosion resistant materials such as type 316 stainless steel are applicable and their performance in CO₂ have been proven during extensive operation in AGRs. In the previous study, the CO₂ cycle gas turbomachinery weight was estimated to be about one-fifth compared with He cycles. The proposed medium temperature CO₂ gas turbine reactor is expected to be an alternative solution to current high-temperature He gas turbine reactors.     

Size dependent hcp-to-fcc transition temperature in Co nanoclusters obtained by ion implantation in silica

In this work we present in situ investigations on the increase of the hcp-to-fcc transition temperature for Co with respect to the bulk value (420 °C) when nanoclusters are considered. Starting from Co:SiO₂ composites obtained by ion implantation with average Co cluster size of about 5 nm, a transition temperature between 800 °C and 900 °C is found upon thermal annealing in vacuum by in situ transmission electron microscopy. Preliminary results on electron irradiation to promote the transition at lower temperatures are presented.     

Gettering layer for oxygen accumulation in the initial stage of SIMOX processing

A cavity layer or nano-bubble layer introduced by He implantation before the oxygen implantation collects the implanted oxygen and increases the oxygen concentration. The average size and density of the oxygen precipitates formed in the initial stage of the separation-by-implanted-oxygen (SIMOX) process is conform with the size and density of the cavities pre-formed by He implantation and annealing. The gettering ability of the cavity layer for oxygen is directly related to the area of the internal surface of the cavities. A nano-bubble layer accumulates oxygen in a very narrow range occurring between the damage maximum, D_P, and the mean projected ion range, R_P. Such a nano-bubble layer is most efficient in oxygen gettering due to their larger area of the internal surface and the small size of the oxide precipitates initially formed at the bubbles.     

Structure and strain measurements on SiC formed by carbon ion implantation

Thin buried silicon carbide layers have been formed by high-dose carbon ion implantation into silicon and subsequent annealing. The formation of SiC during implantation and the structure of carbide layers after annealing are investigated by X-ray diffraction measurements using a four-circle goniometer. A detailed stress analysis of the epitaxially aligned 3C---SiC precipitates formed during implantation is presented. The three-dimensional strain and stress tensors are calculated for different doses. With increasing dose, stress relaxation accompanied by a transition from isotropic to anisotropic strain/stress states is observed. The dose dependence of the peak intensities of 3C---SiC present in the as-implanted state is studied. Stress tensors show a further relaxation in the annealed state.     

Transient radiation effects in CMOS inverters fabricated on SIMOX and BESOI wafers

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High precision Hf ion implantation using a high-current ion implanter

The development of accurate mass spectrometry, enabling the identification of all the ions extracted from the ion source and further precise ¹⁸⁰Hf isotope implantation, in a high current implanter is described. The spectrometry system uses two signals (x-y graphic), one proportional to the magnetic field (x-axes), taken from the high-voltage potential with an optic fiber system, and the other proportional to the beam current intensity (y-axes), taken from a beam-stop. The ion beam mass register in a mass spectrum of all the elements magnetically analyzed with the same radius and defined by a pair of analyzing slits as a function of their beam intensity is presented. Hence, it is possible to implant ¹⁸⁰Hf⁺, with less than 1% contamination from neighboring isotopes, in order to conduct material characterization studies by Perturbed Angular Correlations. The precision of the low fluence ion implantation has been done by neutron activation analysis.     

Distribution of carbon in polycrystalline copper surfaces treated by methane plasma immersion ion implantation

Copper substrates with rather large grains (dimensions of some mm) treated by pulsed methane plasma immersion ion implantation exhibit a laterally inhomogeneous carbon distribution. Areas with high carbon X-ray intensity in electron probe microanalysis coincide with thicker carbon containing layers as seen in sputter depth profiling via secondary ion mass spectrometry. The distribution of carbon within the surface depends not only on the treatment time and pulse repetition rate but also on the orientation of the individual copper grains.     

Irradiation effect of carbon negative-ion implantation on polytetrafluoroethylene for controlling cell-adhesion property

We have investigated the irradiation effect of negative-ion implantation on the changes of physical surface property of polytetrafluoroethylene (PTFE) for controlling the adhesion property of stem cells. Carbon negative ions were implanted into PTFE sheets at fluences of 1 × 10¹⁴-1 × 10¹⁶ ions/cm² and energies of 5-20 keV. Wettability and atomic bonding state including the ion-induced functional groups on the modified surfaces were investigated by water contact angle measurement and XPS analysis, respectively. An initial value of water contact angles on PTFE decreased from 104° to 88° with an increase in ion influence to 1 × 10¹⁶ ions/cm², corresponding to the peak shifting of XPS C1s spectra from 292.5 eV to 285 eV with long tail on the left peak-side. The change of peak position was due to decrease of C-F₂ bonds and increase of C-C bonds with the formation of hydrophilic oxygen functional groups of OH and CO bonds after the ion implantation. After culturing rat mesenchymal stem cells (MSC) for 4 days, the cell-adhesion properties on the C⁻-patterned PTFE were observed by fluorescent microscopy with staining the cell nuclei and their actin filament (F-actin). The clear adhesion patterning of MSCs on the PTFE was obtained at energies of 5-10 keV and a fluence of 1 × 10¹⁵ ions/cm². While the sparse patterns and the uncontrollable patterns were found at a low fluence of 3 × 10¹⁴ ions/cm² and a high fluence of 3 × 10¹⁵ ions/cm², respectively. As a result, we could improve the surface wettability of PTFE to control the cell-adhesion property by carbon negative-ion implantation.