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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

The effect of helium on cavity swelling in dual-ion irradiated Fe and Fe-10Cr ferritic alloys

We report Ferritic-martensitic (FM) steels for in-vessel components in proposed fusion reactors are expected to suffer from high levels of displacement damage and helium (He) generation by neutron transmutation. However, a thorough understanding of the He synergistic effects on the cavity swelling in FM steels is still not well established. To gain fundamental insights into the He effect on cavity swelling, high purity Fe and Fe-10 wt.% Cr ferritic model alloys were irradiated with 8 MeV Ni ions and co-implanted He ions at 400 to 550 °C up to 30 displacements per atom (dpa) with He implantation rates of 0.1, 10 and 50 appm He/dpa. The current study focuses on the 50 appm He/dpa, 500 °C behavior vs. 0.1 and 10 appm He/dpa. Irradiation-induced defects, including cavities, dislocation loops, and dislocation networks were characterized using transmission electron microscopy (TEM). In the grain interior, a bimodal cavity size distribution was observed in the 10 and 50 appm He/dpa samples, but not for 0.1 appm He/dpa. Cavity swelling was maximized at intermediate He implantation rates of ~10 appm He/dpa for both ion-irradiated Fe and Fe-10Cr alloys. The cavity swelling behavior as a function of He implantation rate appears to be controlled by the He/dpa-dependent variation of cavity sink strengths. Treating small bubbles as biased sinks for interstitial absorption can significantly increase the ratio of biased to unbiased sink strengths (Q) and results in maximized cavity swelling for a Q ratio close to one.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Composition and Structure of Ga{sub 1–} {sub x}Na{sub x}As Nanolayers Produced near the GaAs Surface by Na{sup +} Implantation

The composition and structure of nanodimensional Ga{sub 1–} {sub x}Na{sub x}As phases produced by implantation of Na{sup +} ions into the near-surface area of GaAs have been studied by Auger electron spectroscopy and fast electron diffraction. It has been found that the thickness of the ternary epitaxial layer is 10–12 nm for ion energy E{sub 0} = 20 keV. The composition of the three-layer nanosystems is GaAs–Ga{sub 0.5}Na{sub 0.5}As–GaAs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

Effect of implanted species on thermal evolution of ion-induced defects in ZnO

Implanted atoms can affect the evolution of ion-induced defects in radiation hard materials exhibiting a high dynamic annealing and these processes are poorly understood. Here, we study the thermal evolution of structural defects in wurtzite ZnO samples implanted at room temperature with a wide range of ion species (from {sup 11}B to {sup 209}Bi) to ion doses up to 2 × 10{sup 16} cm{sup −2}. The structural disorder was characterized by a combination of Rutherford backscattering spectrometry, nuclear reaction analysis, and transmission electron microscopy, while secondary ion mass spectrometry was used to monitor the behavior of both the implanted elements and residual impurities, such as Li. The results show that the damage formation and its thermal evolution strongly depend on the ion species. In particular, for F implanted samples, a strong out-diffusion of the implanted ions results in an efficient crystal recovery already at 600 °C, while co-implantation with B (via BF{sub 2}) ions suppresses both the F out-diffusion and the lattice recovery at such low temperatures. The damage produced by heavy ions (such as Cd, Au, and Bi) exhibits a two-stage annealing behavior where efficient removal of point defects and small defect clusters occurs at temperatures ∼500 °C, while the second stage is characterized by a gradual and partial annealing of extended defects. These defects can persist even after treatment at 900 °C. In contrast, the defects produced by light and medium mass ions (O, B, and Zn) exhibit a more gradual annealing with increasing temperature without distinct stages. In addition, effects of the implanted species may lead to a nontrivial defect evolution during the annealing, with N, Ag, and Er as prime examples. In general, the obtained results are interpreted in terms of formation of different dopant-defect complexes and their thermal stability.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

The effects of high energy deuteron ion beam irradiation on the tensile behavior of HT-9

Ion beam implantations are widely performed to understand the effects of irradiation-induced displacement damage on nuclear structural materials. However, the volume of material that can be investigated is often limited by the maximum energies of accelerator facilitates, leading to a limitation in the thickness of samples whose mechanical properties can be evaluated. The Lawrence Berkeley National Laboratory’s 88-Inch Cyclotron offers a wide range of ions and energies, allowing for material ion implantations at larger scales than typical. Four HT-9 SS-J-geometry tensile specimens were polished and then irradiated with deuterons at the 88-Inch Cyclotron to doses of approximately 0.2 dpa prior to small scale tensile testing. Here, the results from this study show irradiation hardening characterized by the tensile test results and black dot irradiation defects. Additionally, a comprehensive look at low temperature irradiations of high-Cr F/M steels is presented and our results show agreement with the available data.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structure and optical properties of ZnO with silver nanoparticles

Textured nanocrystalline ZnO thin films are synthesized by ion beam assisted deposition. According to X-ray diffraction data, the crystallite size is ∼25 nm. Thin (∼15 nm) ZnO layers containing Ag nanoparticles are formed in a thin surface region of the films by the implantation of Ag ions with an energy of 30 keV and a dose in the range (0.25–1) × 10{sup 17} ion/cm{sup 2}. The structure and optical properties of the layers are studied. Histograms of the size distribution of Ag nanoparticles are obtained. The average size of the Ag nanoparticles varies from 0.5 to 1.5–2 nm depending on the Ag-ion implantation dose. The optical transmittance of the samples in the visible and ultraviolet regions increases, as the implantation dose is increased. The spectra of the absorption coefficient of the implanted films are calculated in the context of the (absorbing film)/(transparent substrate) model. It is found that the main changes in the optical-density spectra occur in the region of ∼380 nm, in which the major contribution to absorption is made by Ag nanoparticles smaller than 0.75 nm in diameter. In this spectral region, absorption gradually decreases, as the Ag-ion irradiation dose is increased. This is attributed to an increase in the average size of the Ag nanoparticles. It is established that the broad surface-plasmon-resonance absorption bands typical of nanocomposite ZnO films with Ag nanoparticles synthesized by ion implantation are defined by the fact that the size of the nanoparticles formed does not exceed 1.5–2 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2011

In vitro prominent bone regeneration by release zinc ion from Zn-modified implant

Highlights: {yields} We isolated the Zn{sup 2+} ions (eluted Zn{sup 2+} ion; EZ) from zinc-incorporated titanium implant. {yields} The EZ promoted the cell viability in hBMCs. {yields} The EZ stimulated preosteoblast and osteoblast marker gene expression in hBMCs. {yields} The hBMCs supplemented with EZ showed typically cell morphology when osteoblast maturing. {yields} It is revealed that the EZ also stimulates the calcium deposition of hBMCs. -- Abstract: Zinc is one of the trace elements which induce the proliferation and the differentiation of the osteoblast. In the previous study, we found that zinc ions (Zn{sup 2+} ion)-releasing titanium implants had excellent bone fixation using a rabbit femurs model. In this study, we isolated the Zn{sup 2+} ions (eluted Zn{sup 2+} ion; EZ) released from the implant surface, and evaluated the effect of EZ on the osteogenesis of human bone marrow-derived mesenchymal cells (hBMCs). In the result, it was found that the EZ stimulated cell viability, osteoblast marker gene (type I collagen, osteocalcin (OC), alkaline phosphatase (ALP) and bone sialoprotein (BSP)) expressions and calcium deposition in hBMCs.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

X-Ray Photoelectron Spectroscopy of Stabilized Zirconia Films with Embedded Au Nanoparticles Formed under Irradiation with Gold Ions

Nanosized films of stabilized zirconia with Au nanoparticles formed by implanting Au ions are studied by X-ray photoelectron spectroscopy and transmission electron microscopy. The effect of irradiation of films with Au ions and postimplantation annealing on the distribution of chemical elements and zirconium- containing ZrO{sub x} compounds over the depth of the films is studied. Based on the data on the dimensional shift of the Au 4 f photoelectron line, the average value of the nanoparticle size is determined.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Electrical activation and electron spin resonance measurements of arsenic implanted in silicon

The electrical activation of arsenic (As) implanted in Si is investigated with electron spin resonance (ESR), spreading resistance (SR), and secondary ion mass spectroscopy (SIMS). The As ions were implanted with a dose of 1 × 10{sup 12 }cm{sup −2} and subsequently annealed at various temperatures in the range of 500–1100 °C. The ESR measurements at 10 K show that the density of the As donor electrons for all the annealing temperatures is less than 10% of the As atom concentration measured by SIMS. The SR data indicate that the density of conduction band electrons is several times larger than that of the As donor electrons. These results strongly suggest that most of the As donor electrons are ESR inactive at low temperatures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Site specific isolated nanostructure array formation on a large area by broad ion beam without any mask and resist

We report the formation of isolated nanostructure arrays on a large area via broad ion beam implantation without the aid of any mask or resist. Desired ions have been implanted at specific locations of the prefabricated silicon ripple or triangular structures by exploiting the variation of local ion impact angles. We have shown that the implantation of Fe ions on an O{sup +} ions induced pre fabricated triangular shaped patterned Si surface results in a self-organized periodic array of striped magnetic nanostructures having several micron length and about 50 nm width arranged with a spacial separation of ∼200 nm. The morphology, composition, crystalline structure, and magnetic property of these nanopatterns have been analyzed using high-resolution cross-sectional transmission electron microscopy and atomic force microscopy. A geometrical model has been proposed to explain the fundamental features of such ion-induced nanopattern structures.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Distribution of species and Ga–N bonds in silicon co-implanted with gallium and nitrogen ions

The concentration profiles of species in silicon subjected to gallium and nitrogen co-implantation and subsequent annealing have been investigated by the method of X-ray photoelectron spectroscopy combined with the layer-by-layer ion etching of the implanted layer. It is shown that practically entire implanted gallium undergoes out-diffusion, but the preliminary implantation of nitrogen for the synthesis of a barrier SiN{sub x} layer makes it possible to avoid the essential loss of gallium. In this case, about 14 % of implanted gallium bond to nitrogen. The obtained data are discussed from the viewpoint of the possibility of ion synthesis of GaN inclusions in silicon matrix.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Influence of ion source configuration and its operation parameters on the target sputtering and implantation process

In the work, investigation of the features and operation regimes of sputter enhanced ion-plasma source are presented. The source is based on the target sputtering with the dense plasma formed in the crossed electric and magnetic fields. It allows operation with noble or reactive gases at low pressure discharge regimes, and, the resulting ion beam is the mixture of ions from the working gas and sputtering target. Any conductive material, such as metals, alloys, or compounds, can be used as the sputtering target. Effectiveness of target sputtering process with the plasma was investigated dependently on the gun geometry, plasma parameters, and the target bias voltage. With the applied accelerating voltage from 0 to 20 kV, the source can be operated in regimes of thin film deposition, ion-beam mixing, and ion implantation. Multi-component ion beam implantation was applied to {alpha}-Fe, which leads to the surface hardness increasing from 2 GPa in the initial condition up to 3.5 GPa in case of combined N{sub 2}-C implantation. Projected range of the implanted elements is up to 20 nm with the implantation energy 20 keV that was obtained with XPS depth profiling.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Modification of the crystal structure of gadolinium gallium garnet by helium ion irradiation

The structure of gadolinium gallium garnet (GGG) single crystals before and after implantation by He{sup +} ions has been investigated using high-resolution X-ray diffraction methods and the generalized dynamic theory of X-ray scattering. The main types of growth defects in GGG single crystals and radiation-induced defects in the ion-implanted layer have been determined. It is established that the concentration of dislocation loops in the GGG surface layer modified by ion implantation increases and their radius decreases with an increase in the implantation dose.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1977

Effect of surface texture by ion beam sputtering on implant biocompatibility and soft tissue attachment

The objectives in this report were to use the ion beam sputtering technique to produce surface textures on polymers, metals, and ceramics. The morphology of the texture was altered by varying both the width and depth of the square pits which were formed by ion beam erosion. The width of the ribs separating the pits were defined by the mask used to produce the texture. The area of the surface containing pits varies as the width was changed. The biological parameters used to evaluate the biological response to the texture were: (1) fibrous capsule and inflammatory response in subcutaneous soft tissue; (2) strength of the mechanical attachment of the textured surface by the soft tissue; and (3) morphology of the epidermal layer interfacing the textured surface of percutaneous connectors. Because the sputter yield on teflon ribs was approximately an order of magnitude larger than any other material the majority of the measurements presented in the report were obtained with teflon.

Gibbons, D. F.↗
NASA NTRS1988

GaAs/GaAlAs distributed Bragg reflector laser with a focused ion beam, low dose dopant implanted grating

The performance of a GaAs/GaAlAs distributed Bragg reflector (DBR) laser using a focused ion beam implanted grating (FIB-DBR) is reported for the first time. Stripes of Si(2+) with a period of 2300 A and a dose about 10 to the 14th/sq cm are directly implanted into the passive large optical cavity layer to provide the distributed feedback. Surface-emitting light from the second-order grating is observed. Threshold current of 110 mA and single DBR mode operation from 20 to 40 C are obtained. The wavelength tuning rate with temperature is 0.8 A/C. The coupling coefficient is estimated to be 15/cm. The results show that FIB technology is practical for distributed feedback and DBR lasers and optoelectronic integrated circuits.

Wu, M. C.↗
DOE OSTI2019

Extremely large d 0 magnetism in krypton implanted polar ZnO films

Magnetization is produced in samples of ZnO by implanting krypton ions. Krypton is chemically inert; hence, the magnetization is the consequence of the radiation damage that occurred due to the implantation process. We have found magnetization as large as 185 emu cm –3 at room temperature which corresponds to a moment of ~40 Bohr magnetons per implanted krypton ion. The results are compared for implantation into different ZnO samples, O- and Zn-polar thin films and thin ZnO crystal wafers. The structure of the films has been investigated using RHEED, AFM, XRD and EXAFS. The O-polar film grew in a layer-by-layer mode and after implantation, its lattice spacing increased and the grain size decreased which indicated that the Kr atoms had been incorporated into the lattice. In contrast the Zn-polar film grew in a Stranski–Krastanov mode and its lattice spacing and grain size were almost unchanged by the implantation indicating that the Kr atoms were in the grain boundaries. Raman scattering is used to characterize the radiation damage and to identify scattering from amorphous regions in the grain boundaries and the scattering from point defects. The largest magnetization is found in the O-polar ZnO films where there is a marked grain fragmentation, leading to an increase in the volume of the sample occupied by grain boundaries. As a result, the increase in the number of point defects, which was identified by Raman scattering for films of both polarity, was less effective at producing a magnetic signal than the grain boundaries.

36 MATERIALS SCIENCE↗
DOE OSTI2015

An origin of orange (2 eV) photoluminescence in SiO{sub 2} films implanted with high Si{sup +}-ion doses

The photoluminescence and photoluminescence excitation spectra of SiO{sub 2} films implanted with high (3 at %) Si{sup +}-ion doses are studied in relation to the temperature of postimplantation annealing. It is shown that two photoluminescence bands with peaks at 2.7 and 2 eV are dominant in the spectra. As the annealing temperature is increased, the relation between the intensities of the 2.7 and 2 eV bands changes in favor of the former one. Both of the photoluminescence bands have their main excitation peak at the energy 5.1 eV. The excitation spectrum of the ∼2-eV band exhibits also peaks at 3.8 and 4.6 eV. It is concluded that, in the implanted SiO{sub 2} films, the orange photoluminescence band originates from radiative transitions between levels of centers associated with a deficiency of oxygen (≡Si–Si≡ or =Si:) and the levels of nonbridging oxygen (≡Si–O•)

36 MATERIALS SCIENCE↗
DOE OSTI2016

Ion beam synthesis of ZrC{sub x}O{sub y} nanoparticles in cubic zirconia

{110}-oriented yttria-stabilized zirconia single crystals have been implanted with low-energy C ions in an axial direction, at room temperature and at 550 °C. Room temperature ion implantation generated a damage layer that contains the expected dislocation loop clusters. Strikingly, the high temperature implantation produced zirconium oxycarbide nanoparticles (ZrC{sub x}O{sub y}) at a shallow depth in the yttria-stabilized cubic zirconia crystal, with a diameter in the range of 4–10 nm. Moreover, in the high concentration region of implanted C ions, between 100 and 150 nm below the surface, a number of large precipitates, up to 20 nm, were observed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1972

On the origins of trapped helium, neon and argon isotopic variations in meteorites. I - Gas-rich meteorites, lunar soil and breccia. II - Carbonaceous meteorites.

Data are presented from stepwise heating experiments and total extractions on five meteorites: Kapoeta, Fayetteville, Holman Island, Cee Vee, and Pultusk. These data reveal the presence of four isotopically distinct trapped neon components. A comparison of trapped neon with trapped helium and argon in bulk analyses indicates the existence of correlated helium, neon and argon isotopic structures. Component B is attributed primarily to direct implantation of rare gas ions by the present day solar wind. Component C is identified with directly implanted low energy (1-10 Mev/n) solar flare rare gases. Component D is associated with rare gas ions implanted in meteoritic material by the primitive, pre-main sequence, solar wind. A fourth component, observed only in Kapoeta and the lunar fines and breccia, is tentatively attributed to parent body 'atmospheric' ions implanted in surface material by a solar wind induced electric field.

Black, D. C.↗