The structural and optical properties of carbon nanoclusters formed in thermally grown silicon dioxide film via the ion beam synthesis process have been investigated. A low-energy (70 keV) carbon ion beam (C−) at a fluence of 3 × 1017 atoms/cm2 was used for implantation into a thermally grown silicon dioxide layer (500 nm thick) on a Si (100) wafer. Several parts of the implanted samples were subsequently annealed in a gas mixture (4 % H2 + 96 % Ar) at 900 °C for different time periods. The as-implanted and annealed samples were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). The carbon ion implantation depth profile was simulated using a widely used Monte Carlo-based simulation code SRIM-2012. Additionally, the elemental depth profile of the implanted carbon along with host elements of silicon and oxygen were simulated using a dynamic ion–solid interaction code T-DYN, which incorporates the effects of the surface sputtering and gradual change in the elemental composition in the implanted layers due to high-fluence ion implantation. The elemental depth profile obtained from the XPS measurements matches closely to the T-DYN predictions. Raman measurements indicate the formation of graphitic phases in the annealed samples. The graphitic peak (G-peak) was found to be increased with the annealing time duration. In the sample annealed for 10 min, the sizes of the carbon nanoclusters were found to be 1–4 nm in diameter using TEM. The PL measurements at room temperature using a 325-nm laser show broad-band emissions in the ultraviolet to visible range in the as-implanted sample. Intense narrow bands along with the broad bands were observed in the annealed samples. The defects present in the as-grown samples along with carbon ion-induced defect centers in the as-implanted samples are the main contributors to the observed broad-band luminescence centered around 2.4 and 2.9 eV. The intense narrow peaks observed in the PL spectra centered on ~2.67 and 2.8 eV with full width at half maxima ≤ 150 meV are believed to be mainly due to the quantum size effects of the carbon nanoclusters formed in the annealed samples. The relative intensities of the narrow peaks are seen to be changing with the annealing time interval. This may be due to the change in the size distribution of the carbon nanoclusters.

Amorphous carbon (a-C) nanoclusters were synthesized by the implantation of carbon ions (C-) into thermally grown silicon dioxide film (-500 nm thick) on a Si (100) wafer and processed by high temperature thermal annealing. The carbon ions were implanted with an energy of 70 keV at a fluence of 5 x 10(17) atoms/cm2. The implanted samples were annealed at 1100 degrees C for different time periods in a gas mixture of 96% Ar+4% H2. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM) were used to study the structural properties of both the as-implanted and annealed samples. HRTEM reveals the formation of nanostructures in the annealed samples. The Raman spectroscopy also confirms the formation of carbon nano-clusters in the samples annealed for 10 min, 30 min, 60 min and 90 min. No Raman features originating from the carbon-clusters are observed for the sample annealed further to 120 min, indicating a complete loss of implanted carbon from the SiO2 layer. The loss of the implanted carbon in the 120 min annealed sample from the SiO2 layer was also observed in the XPS depth profile measurements. Room temperature photoluminescence (PL) spectroscopy revealed visible emissions from the samples pointing to carbon ion induced defects as the origin of a broad 2.0-2.4 eV band, and the intrinsic defects in SiO2 as the possible origin of the -2.9 eV bands. In low temperature photoluminescence spectra, two sharp and intense photoluminescence lines at -3.31 eV and -3.34 eV appear for the samples annealed for 90 min and 120 min, whereas no such bands are observed in the samples annealed for 10 min, 30 min, and 60 min. The Si nano-clusters forming at the Si-SiO2 interface could be the origin of these intense peaks.

A detailed XPS analysis has been performed to observe the effect of carbon ion fluences in the formation of β-SiC by ion implantation. Carbon ion fluences of 1×1017, 2×1017, 5×1017, and 8×1017atoms/cm2 at an ion energy of 65keV have been used to implant Si at room temperature. The implanted samples were annealed at 1100°C for 1h in a mixture of Ar 96% and H2 4%. The compositional depth profile along with the change in the chemical state of the implanted carbon and silicon in the annealed samples has been measured. The effect of ion fluences in the formation of SiC has been discussed in reference to binding energy shifts and integrated peak intensities of C 1s and Si 2p signals. It has been observed that the implanted carbon is totally consumed to make Si–C bonds for samples implanted at fluences of 1×1017, 2×1017, and 5×1017atoms/cm2. However, for the sample at a fluence of 8×1017atoms/cm2, a portion of the implanted carbon is found to be in the form of C–C bonds in the compositional depth profile peak position.

A systematic study has been performed to synthesize buried homogeneous layers of β-SiC by multiple energies (15–65keV) of carbon ion implantations into Si(100), followed by high temperature thermal annealing. A continuous stoichiometric SiC layer of 170nm thickness has been formed in the implanted region when the sample was annealed at 1100°C for 1h. The formation of a β-SiC thin film has been confirmed by using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy techniques.

The M-shell x-ray production cross sections for thorium and uranium have been measured for carbon ions with energies from 4.5 to 11.3 MeV with the charge state q increasing from 2 to 4, and oxygen ions with energies from 4.5 to 13.5 MeV with the charge state q increasing from 2 to 5. These cross sections are compared to the predictions of the first Born (PWBA+OBKN) and ECUSAR ionization theories, which were evaluated in a novel manner for the C+q and O+q energies and charge states of the data and converted to x-ray production cross sections with atomic parameters for a singly ionized M-shell and multiple ionization in the outer shells. Individual groups of M-shell transitions are also compared to the two ionization theories. The ECUSAR theory is shown to describe the measurements better than the first Born approximation. It is found to be in generally good agreement for all the total M-shell x-ray production and M-shell lines except for the Mγ cross sections. Reasons for the overestimation of the Mγ data are discussed.

A systematic study of the formation of buried β-SiC structures by carbon ion implantation into Si followed by high-temperature thermal annealing has been carried out. A high fluence of carbon ions (8 × 1017 atoms/cm2) was implanted at 65 keV energy. Formation of the crystalline β-SiC phase was monitored by Fourier-transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) techniques. The implanted samples were annealed at 900°C and 1100°C to observe the effects of annealing temperature on the formation of crystalline β-SiC. Formation of crystalline β-SiC was clearly observed in the sample annealed at 1100°C in a flowing nitrogen environment for a period of 1 h. Graphitic carbon clusters were observed at the implanted carbon profile peak position by XPS depth profile measurements. Various structural defects such as grain boundaries were also visualized in the annealed sample by high-resolution TEM.

The β-SiC nanocrystals were synthesized by the implantation of carbon ions (C−) into silicon followed by high-temperature annealing. The carbon fluences of 1×1017, 2×1017, 5×1017, and 8×1017 atoms/cm2 were implanted at an ion energy of 65 keV. It was observed that the average size of β-SiC crystals decreased and the amount of β-SiC crystals increased with the increase in the implanted fluences when the samples were annealed at 1100 °C for 1 h. However, it was observed that the amount of β-SiC linearly increased with the implanted fluences up to 5×1017 atoms/cm2. Above this fluence the amount of β-SiC appears to saturate. The Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, and X-ray diffraction (XRD) techniques were used to characterize the samples.

Even though silicon is optically inactive, the nanoscale particle structures (e.g. SiC) in Si or silica matrices are potential candidates for light emitting solid state device applications with higher operation temperatures. The synthesis of these nanostructures involves ion implantation and subsequent thermal annealing. The film thicknesses and sizes of the nanostructures can be controlled by ion energy, fluence, and annealing conditions. Particle accelerator based characterization was used at different stages of formation and analysis of these nanosystems in Si. Results will be presented using infrared spectroscopy (IR), X-ray diffraction spectroscopy (XRD), and photoluminescence (PL) spectroscopy.

A thin film of Ge-rich Ge x Si1−x on a (100) Si substrate was synthesized by ion implantation followed by thermal oxidation. Proper oxidation conditions were maintained to produce a film with Ge atomic content of more than 95%, confirmed by both high-resolution Rutherford backscattering spectrometry (RBS) and Raman spectroscopy. The strain state of the Ge-rich thin film is a function of its thickness, as determined by the implantation fluence. The use of Raman spectroscopy to monitor the composition and strain state of the Ge thin film formed is discussed.

espanolUn Laboratorio de gases ionicos (IBL, por sus siglas en ingles, Ion Beam Laboratory) se esta construyendo actualmente en el Laboratorio Nacional Sandia en Albuquerque, Nuevo Mexico, USA. Tres aceleradores existentes se moveran al IBL y dos mas seran adquiridos para reemplazar los sistemas actuales. El IBL tendra una extensa proteccion contra la radiacion que permitira realizar muchos experimentos nuevos que se discuten en este articulo. Este articulo tambien provee detalles sobre los calculos exhaustivos relacionados con el transporte radiactivo que se emplearon para determinar el grueso y la altura de las vallas/paredes protectoras. EnglishA new Ion Beam Laboratory (IBL) is currently under construction at Sandia National Laboratory in Albuquerque, NM, USA. Three existing accelarators will be moved to the IBL, and two more will be purchased to replace existing systems. The IBL will have extensive radiation shielding that will enable a number of new experiments that will be discussed in this paper. This paper also provides the details of extensive radiation transport calculations that were used to determine the thickness and height of the shield walls.

This paper has been withdrawn keeping in view of publication elsewhere with some appropriate modifications.

M-shell x-ray production cross sections for thorium and uranium have been determined for protons of energies 0.4-4.0 MeV and helium ions of energies 0.4-6.0 MeV. The M-shell line and total M-shell x-ray production cross sections are compared to the predictions of the first Born approximation and ECUSAR ionization theory using recently recommended atomic parameters. Both theories are in good agreement with the data for protons and He ions above 1 MeV. The data of others for energies above 1 MeV protons on uranium, however, fall significantly under the present measurements. Below 1 MeV, with decreasing energy of these projectiles, the first Born approximation increasingly overestimates our measurements while the ECUSAR theory underestimates them to a similar degree. The same trends are seen versus the data of others.

Compact active interrogation sources are being developed that use low‐energy (kilovolt) nuclear reactions to produce high‐energy (megavolt) neutrons or gamma‐rays. We are evaluating target materials for these interrogation sources by performing rapid thermal load and high power density tests that reach conditions expected during source operation. Following the tests, the targets are analyzed with low and high resolution microscopes to assess whether any physical or structural damage has occurred. This paper presents results of the examinations of LiF, Li2O, LiNbO3, CaF2, B4C, and LaB6 target materials following rapid thermal and electron beam heating tests.

The Time Between Photons theory (hereafter TBP) is applied to the evaluation of the lifetime of phosphors employed in the Ion Photon Emission Microscope (IPEM). IPEM allows Radiation Effects Microscopy (REM) without focused ion beams and appears to be the best tool for the radiation hardness assessment of modern integrated circuit at cyclotron energies. IPEM determines the impact point of a single ion onto the sample by measuring the light spot produced on a thin phosphor layer placed on the sample surface. The spot is imaged by an optical microscope and projected at high magnification onto a Position Sensitive Detector (PSD). Phosphors, when excited by an ion, emit photons with a particular lifetime, which is important to evaluate. We measured the statistical distribution of the Time Between consecutive detected Photons (TBP) for several phosphors and have been able to link it to their lifetime employing a theory that is derived in this paper. The single-photon signals are provided by the IPEM-PSD, or faster photomultipliers when high-speed materials had to be assessed.

Carbon-based nanocrystals, formed in silica by low-energy carbon implantation and subsequent thermal annealing, have been previously reported, but ambiguities as to the equilibrium morphology and its relationship to the source of photoluminescence. In our study, silica samples were implanted with 2.0x 1017 atoms/cm(2) C- ions at energies of 8.5 keV, 40 keV and 70 keV. Samples were annealed for 15, 30, 60, 120, 240 minutes at 1100 degrees C in a forming gas (4%H-2+96%Ar). Rutherford backscattering (RBS), particle induced x-ray emission (PIXE), and photoluminescence (PL) were used to characterize the nanocrystals formed by these conditions. The resulting photoluminescence analysis indicated that the size distribution of the nanocrystals could be tailored to yield a broad spectral output between 2.0-2.8 eV by controlling the formation parameters. Also a few notable factors, such as liberation of oxygen in the silica during implantation, as well as uptake of ambient oxygen in the annealing furnace, will be shown to play a critical role in the formation process. Additional passivation with 96%Ar+4%H-2 at a lower temperature (600 degrees C) had little effect. The results of this work will be presented and compared to previous studies.

Direct bandgap emission was observed from quantum confined Silicon nanoparticles synthesized by a novel dual-ion beam implantation technique. Quantum dots (QDs) were formed due to recrystallization of silicon in the amorphous layer due to the irradiation of high energy ions (similar to MeV). Structural analysis such as High Resolution Transmission Electron Microscopy (HRTEM) and X-ray confirm the formation of silicon QDs. FTIR absorption spectroscopy was performed to analyze the formation of silicon quantum dots due to annealing of the ion-implanted samples Strong room-temperature emission (with FWHM similar to 87 meV) was observed from the Si quantum dots which splits into multiple lines at lower temperature The splitting of PL peak observed at lower temperature has been analyzed using the effective mass approximation

Low energy (55 KeV) Osmium ( Os− ) negative ion beam was used to implant (5×1016 atoms/cm2 ) into p-type-Si (100). The implantation was performed with the ion source of a National Electrostatic Corp. 3 MV Tandem accelerator. The implanted sample was subsequently annealed at 650 °C in a gas mixture that was 4% H2 + 96% Ar. Rutherford Backscattering spectrometry (RBS) analysis with 1.5 MeV Alpha particles was used to monitor the precipitate formation. Photoluminescence (PL) measurements were also performed to study possible applications of silicides in light emission. Cross-sectional Scanning Electron Microscopy (X-SEM) was performed for topographic image of the implanted region. RBS along with PL measurements indicate that the presence of osmium silicide (Os2Si3) phase for light emission in the implanted region of the sample.

Radiation effects microscopy (REM) for the next generation integrated circuits (ICs) will require GeV ions both to provide high ionization and to penetrate the thick overlayers in present day ICs. These ion beams can be provided by only a few cyclotrons in the world. Since it is extremely hard to focus these higher-energy ions, we have proposed the ion photon emission microscope (IPEM) that allows the determination of the ion hits by focusing the emitted photons to a position sensitive detector. The IPEM needs a thin luminescent foil that has high brightness, good spatial resolution and does not change the incident ion’s energy and direction significantly. Available organic-phosphor foils require a large thickness to produce enough photons, which results in poor spatial resolution. To solve this problem, we have developed thin, lightly doped n-type GaN films that are extremely bright. We have grown high quality GaN films on sapphire using metal organic chemical vapor deposition (MOCVD), detached the films from the substrate using laser ablation, and made them self-supporting. The smallest foils have 1mm2 area and 1μm thickness. The optical properties, such as light yield, spectrum and decay times were measured and compared to those of conventional phosphors, by using both alpha particles from a radioactive source and 250keV ions from an implanter. We found that the GaN performance strongly depends on composition and doping levels. The conclusion is that 1–2μm GaN film of a 1mm2 area may become an ideal ion position detector.