Showing papers on "Ion beam deposition published in 2017"

IOP : Ion beam production and study of radioactive isotopes with the laser ion source at ISOLDE

Abstract: At ISOLDE the majority of radioactive ion beams are produced using the resonance ionization laser ion source (RILIS). This ion source is based on resonant excitation of atomic transitions by wavelength tunable laser radiation. Since its installation at the ISOLDE facility in 1994, the RILIS laser setup has been developed into a versatile remotely operated laser system comprising state-of–the-art solid state and dye lasers capable of generating multiple high quality laser beams at any wavelength in the range of 210–950 nm. A continuous programme of atomic ionization scheme development at CERN and at other laboratories has gradually increased the number of RILIS-ionized elements. At present, isotopes of 40 different elements have been selectively laser-ionized by the ISOLDE RILIS. Studies related to the optimization of the laser–atom interaction environment have yielded new laser ion source types: the laser ion source and trap and the versatile arc discharge and laser ion source. Depending on the specific experimental requirements for beam purity or versatility to switch between different ionization mechanisms, these may offer a favourable alternative to the standard hot metal cavity configuration. In addition to its main purpose of ion beam production, the RILIS is used for laser spectroscopy of radioisotopes. In an ongoing experimental campaign the isotope shifts and hyperfine structure of long isotopic chains have been measured by the extremely sensitive in-source laser spectroscopy method. The studies performed in the lead region were focused on nuclear deformation and Journal of Physics G: Nuclear and Particle Physics J. Phys. G: Nucl. Part. Phys. 44 (2017) 084006 (28pp) https://doi.org/10.1088/1361-6471/aa78e0 * This article belongs to the Focus on Exotic Beams at ISOLDE: A Laboratory Portrait special issue. 0954-3899/17/084006+28$33.00 © 2017 IOP Publishing Ltd Printed in the UK 1 Made open access 7 August 2017 Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. shape coexistence effects around the closed proton shell Z = 82. The paper describes the functional principles of the RILIS, the current status of the laser system and demonstrated capabilities for the production of different ion beams including the high-resolution studies of short-lived isotopes and other applications of RILIS lasers for ISOLDE experiments.

Resolution of the carbon contamination problem in ion irradiation experiments

Abstract: The widely experienced problem of carbon uptake in samples during ion irradiation was systematically investigated to identify the source of carbon and to develop mitigation techniques. Possible sources of carbon included carbon ions or neutrals incorporated into the ion beam, hydrocarbons in the vacuum system, and carbon species on the sample and fixture surfaces. Secondary ion mass spectrometry, atom probe tomography, elastic backscattering spectrometry, and principally, nuclear reaction analysis, were used to profile carbon in a variety of substrates prior to and following irradiation with Fe 2+ ions at high temperature. Ion irradiation of high purity Si and Ni, and also of alloy 800H coated with a thin film of alumina eliminated the ion beam as the source of carbon. Hydrocarbons in the vacuum and/or on the sample and fixtures was the source of the carbon that became incorporated into the samples during irradiation. Plasma cleaning of the sample and sample stage, and incorporation of a liquid nitrogen cold trap both individually and especially in combination, completely eliminated the uptake of carbon during heavy ion irradiation. While less convenient, coating the sample with a thin film of alumina was also effective in eliminating carbon incorporation.

Mass, mobility and MSn measurements of single ions using charge detection mass spectrometry

Abstract: Charge detection mass spectrometry is used to measure the mass, charge, MSn and mobility of an individual ion produced by electrospray ionization of a 8 MDa polyethylene glycol sample. The charge detection mass spectrometer is an electrostatic ion trap that uses cone electrodes and a single tube detector and can detect ions for up to the full trapping time of 4.0 s. The time-domain signal induced on the detector tube by a single multiply charged ion can be complex owing to sequential fragmentation of the original precursor ion as well as increasing oscillation frequencies of the single ion owing to collisions with background gas that reduce the kinetic energy of the ion inside the trap. Simulations show that the ratio of the time for the ion to turn around inside the cone region of the trap to the time for the ion to travel through the detector tube is constant with m/z and increases with the ion energy per charge. By measuring this ratio, the kinetic energy of an ion can be obtained with good precision (∼1%) and this method to measure ion kinetic energies eliminates the necessity of ion energy selection prior to trapping for high precision mass measurement of large molecules in complex mixtures. This method also makes it possible to measure the masses of each sequential fragment ion formed from the original precursor ion. MS7 of a single multiply charged PEG molecule is demonstrated, and from these ion energy measurements and effects of collisions on the ion motion inside the trap, information about the ion mobility of the precursor ion and its fragments is obtained.

Multiple ion beam irradiation for the study of radiation damage in materials

Abstract: The effects of transmutation produced helium and hydrogen must be included in ion irradiation experiments to emulate the microstructure of reactor irradiated materials. Descriptions of the criteria and systems necessary for multiple ion beam irradiation are presented and validated experimentally. A calculation methodology was developed to quantify the spatial distribution, implantation depth and amount of energy-degraded and implanted light ions when using a thin foil rotating energy degrader during multi-ion beam irradiation. A dual ion implantation using 1.34 MeV Fe + ions and energy-degraded D + ions was conducted on single crystal silicon to benchmark the dosimetry used for multi-ion beam irradiations. Secondary Ion Mass Spectroscopy (SIMS) analysis showed good agreement with calculations of the peak implantation depth and the total amount of iron and deuterium implanted. The results establish the capability to quantify the ion fluence from both heavy ion beams and energy-degraded light ion beams for the purpose of using multi-ion beam irradiations to emulate reactor irradiated microstructures.

Intense highly charged ion beam production and operation with a superconducting electron cyclotron resonance ion source

Abstract: Author(s): Zhao, HW; Sun, LT; Guo, JW; Lu, W; Xie, DZ; Hitz, D; Zhang, XZ; Yang, Y | Abstract: The superconducting electron cyclotron resonance ion source with advanced design in Lanzhou (SECRAL) is a superconducting-magnet-based electron cyclotron resonance ion source (ECRIS) for the production of intense highly charged heavy ion beams. It is one of the best performing ECRISs worldwide and the first superconducting ECRIS built with an innovative magnet to generate a high strength minimum-B field for operation with heating microwaves up to 24-28 GHz. Since its commissioning in 2005, SECRAL has so far produced a good number of continuous wave intensity records of highly charged ion beams, in which recently the beam intensities of Ar4012+ and Xe12926+ have, for the first time, exceeded 1 emA produced by an ion source. Routine operations commenced in 2007 with the Heavy Ion accelerator Research Facility in Lanzhou (HIRFL), China. Up to June 2017, SECRAL has been providing more than 28,000 hours of highly charged heavy ion beams to the accelerator demonstrating its great capability and reliability. The great achievement of SECRAL is accumulation of numerous technical advancements, such as an innovative magnetic system and an efficient double-frequency (24+18 GHz) heating with improved plasma stability. This article reviews the development of SECRAL and production of intense highly charged ion beams by SECRAL focusing on its unique magnet design, source commissioning, performance studies and enhancements, beam quality and long-term operation. SECRAL development and its performance studies representatively reflect the achievements and status of the present ECR ion source, as well as the ECRIS impacts on HIRFL.

Modification of graphene by ion beam

Abstract: Ion induced defect generation in graphene was analyzed using Raman spectroscopy. A single layer graphene membrane produced by chemical vapor deposition (CVD) on copper foil and then transferred on glass substrate was subjected to helium, carbon, nitrogen, argon and krypton ions bombardment at energies from the range 25 keV to 100 keV. A density of ion induced defects and theirs mean size were estimated by using Raman measurements. Increasing number of defects generated by ion with increase of ion mass and decrease of ion energy was observed. Dependence of ion defect efficiency (defects/ion) on ion mass end energy was proportional to nuclear stopping power simulated by SRIM. No correlation between ion defect efficiency and electronic stopping power was observed.

Self-Assembled Gold Nano-Ripple Formation by Gas Cluster Ion Beam Bombardment

Abstract: In this study, we used a 30 keV argon cluster ion beam bombardment to investigate the dynamic processes during nano-ripple formation on gold surfaces. Atomic force microscope analysis shows that the gold surface has maximum roughness at an incident angle of 60° from the surface normal; moreover, at this angle, and for an applied fluence of 3 × 1016 clusters/cm², the aspect ratio of the nano-ripple pattern is in the range of ~50%. Rutherford backscattering spectrometry analysis reveals a formation of a surface gradient due to prolonged gas cluster ion bombardment, although the surface roughness remains consistent throughout the bombarded surface area. As a result, significant mass redistribution is triggered by gas cluster ion beam bombardment at room temperature. Where mass redistribution is responsible for nano-ripple formation, the surface erosion process refines the formed nano-ripple structures.

Current developments with TRIUMF’s titanium-sapphire laser based resonance ionization laser ion source

Abstract: Developments at TRIUMF’s isotope separator and accelerator (ISAC) resonance ionization laser ion source (RILIS) in the past years have concentrated on increased reliability for on-line beam delivery of radioactive isotopes to experiments, as well as increasing the number of elements available through resonance ionization and searching for ionization schemes with improved efficiency. The current status of these developments is given with a list of two step laser ionization schemes implemented recently.

A Small Spot, Inert Gas, Ion Milling Process as a Complementary Technique to Focused Ion Beam Specimen Preparation.

Abstract: This paper reports on the substantial improvement of specimen quality by use of a low voltage (0.05 to ~1 keV), small diameter (~1 μm), argon ion beam following initial preparation using conventional broad-beam ion milling or focused ion beam. The specimens show significant reductions in the amorphous layer thickness and implanted artifacts. The targeted ion milling controls the specimen thickness according to the needs of advanced aberration-corrected and/or analytical transmission electron microscopy applications.

High-brightness Cs focused ion beam from a cold-atomic-beam ion source.

Abstract: We present measurements of focal spot size and brightness in a focused ion beam system utilizing a laser-cooled atomic beam source of Cs ions. Spot sizes as small as (2.1 ± 0.2) nm (one standard deviation) and reduced brightness values as high as (2.4 ± 0.1) × 107 A m−2 Sr−1 eV−1 are observed with a 10 keV beam. This measured brightness is over 24 times higher than the highest brightness observed in a Ga liquid metal ion source. The behavior of brightness as a function of beam current and the dependence of effective source temperature on ionization energy are examined. The performance is seen to be consistent with earlier predictions. Demonstration of this source with very high brightness, producing a heavy ionic species such as Cs+, promises to allow significant improvements in resolution and throughput for such applications as next-generation circuit edit and nanoscale secondary ion mass spectrometry.

Infrared ion spectroscopy inside a mass-selective cryogenic 2D linear ion trap

Abstract: We demonstrate operation of the first cryogenic 2D linear ion trap (LIT) with mass-selective capabilities. This trap presents a number of advantages for infrared ion "action" spectroscopy studies, particularly those employing the "tagging/messenger" spectroscopy approach. The high trapping efficiencies, trapping capacities, and low detection limits make 2D LITs a highly suitable choice for low-concentration analytes from scarce biological samples. In our trap, ions can be cooled down to cryogenic temperatures to achieve higher-resolution infrared spectra, and individual ions can be mass selected prior to irradiation for a background-free photodissociation scheme. Conveniently, multiple tagged analyte ions can be mass isolated and efficiently irradiated in the same experiment, allowing their infrared spectra to be recorded in parallel. This multiplexed approach is critical in terms of increasing the duty cycle of infrared ion spectroscopy, which is currently a key weakness of the technique. The compact design of this instrument, coupled with powerful mass selection capabilities, set the stage for making cryogenic infrared ion spectroscopy viable as a bioanalytical tool in small molecule identification.

TNSA and ponderomotive plasma production in enriched carbon polyethylene foils

Abstract: Proton and carbon ion acceleration in a target-normal-sheath-acceleration regime produced by a laser intensity of 1016 W/cm2 was investigated using thin polyethylene foils. Measurements performed at the PALS facility in Prague demonstrate forward ion acceleration above 1 MeV per charge state. The ion acceleration is higher in thinner polymeric foils. In order to increase the emission yield of the proton and carbon ions, the target thickness should be enhanced, but this choice reduces drastically the ion acceleration. The use of highly absorbing stuff, such as carbon nanotubes embedded inside a polymer, enhances the ion acceleration but results in a broad ion energy distribution and a low amount of the highly accelerated ion species.

Study of the microstructure and surface morphology of silver nanolayers obtained by ion-beam deposition

Abstract: The aim of this research is to fabricate Ag nanoparticle assemblies forming nanolayers with different thicknesses in order to evaluate their physical properties and their 3-D (three-dimensional) surface micromorphology. Such Ag nanolayers were deposited by physical vapor deposition methods under ion-beam irradiation in argon atmosphere at room temperature. X-ray diffraction (XRD) characterizations confirmed the formation of silver nanocrystals. Using surface field parameters, which were derived from atomic force microscopy (AFM) analysis, the surface morphology of the nanolayers were described according ISO 25178-2:2012. The height and slope distribution functions, together with the autocorrelation (ACF), the height–height correlation (HHCF) and the power spectral density (PSDF) functions were determined for the different analyzed samples using linear interpolation in the horizontal direction. All samples had a fractal character with a fractal dimension of 2.54 ± 0.01 independent of the film thickness.

Lead-silicate glass surface sputtered by an argon cluster ion beam investigated by XPS

Abstract: The conventional ion beam sputter-cleaning technique is frequently used for removing surface adsorbates and carbon contamination from air-exposed glass surfaces. Due to the ion-surface interaction, however, an altered near-surface layer is formed with a modified composition and modified bonding. In the present work, we first examine changes in surface composition and bonding due to X-ray and electron irradiation for both air-exposed and sputter-cleaned surfaces. Then we apply argon cluster ion beam sputtering, known as a very gentle technique with respect to the changes in surface chemistry, to air-exposed lead-silicate glass surfaces analyzed by high-energy resolved core-level photoelectron spectroscopy. It was found that (i) the surface contamination present on air-exposed lead-silicate glass surfaces has a qualitative influence on the results of an XPS analysis, and (ii) Ar cluster ion beam sputter-cleaning with mean energy per Ar atom in clusters of a few eV was successfully used to remove surface contamination from air-exposed lead-silicate glass with no substantial violation of the glass surface structure. This made it easier to reveal their intrinsic surface properties.

Reactive ion beam sputtering of Ti: Influence of process parameters on angular and energy distribution of sputtered and backscattered particles

Abstract: This work focuses on the angular and energy distribution of secondary particles during the ion beam sputtering of a Ti target in a reactive oxygen atmosphere. The influence of ion species, ion energy, and scattering geometry (ion incidence angle and polar emission angle) was investigated systematically. Ion energies of 0.5, 1.0, and 1.5 keV and an ion current of roughly 10 mA were used to sputter deposit TiO2 films from a pure Ti target at an operating pressure of 5.0 × 10−5 and 6.5 × 10−5 mbar and an oxygen partial pressure of 1.0 × 10−5 and 2.5 × 10−5 mbar for sputtering with Ar and Xe ions, respectively. The angular distribution of the flux of sputtered Ti particles was determined by measuring the thickness of TiO2 films. The flux of sputtered Ti particles is described by the superposition of an isotropic and anisotropic part. The isotropic part increases when increasing ion energy, decreasing the incidence angle, or changing the sputtering gas from Xe to Ar. An energy-selective mass spectrometer was u...

Nuclear microprobe performance in high-current proton beam mode for micro-PIXE

Abstract: The performance of a nuclear microprobe is dominantly determined by the brightness of the injected ion beam. At Jožef Stefan Institute (JSI), negative hydrogen ion beams are created in a multicusp ion source and injected into a 2 MV tandetron accelerator. The output characteristics of the multicusp ion source were tuned in order to obtain matching proton beam intensities for the ion accelerator and for the object slits as well. For the optimal focusing of the proton beam in a high-current mode (I > 100 pA) to the sub-micrometer dimensions, dedicated thin nanostructures with sharp edges have been manufactured. Set of nanostructures was micromachined by focused ion beam (FIB) at film reference material, produced by Institute for Reference Materials and Measurements (IRMM) and constituted of 57 μg/cm 2 of titanium on vitreous carbon substrate. The proton beam profiles were measured by beam scans across the nanostructures over long measuring times, indicating eventual slow drifts of the sample from a reference beam direction. Overall, proton beam dimensions of 600 nm were obtained, demonstrating appropriate stability for micro-PIXE (micro-Particle Induced X-ray Emission) at sub-micrometer resolution for elemental analysis of biological tissue samples prepared in a freeze-dried state or in a frozen-hydrated state. The resulting performance required for micro-PIXE analysis in a high current mode with a 3 MeV proton beam is presented.

Study of the beam profile and position instability of a post-accelerated pseudospark-sourced electron beam

Abstract: A pseudospark-sourced electron beam is a promising candidate for driving a THz millimeter wave radiation source. However, the physics governing the electron beam density profile and the beam center deviation from the axis of the structure, which may be caused by the randomness in the pseudospark discharge process, remains still unclear especially for the high energy component of the pseudospark-sourced electron beam, which is usually non-mono-energetic. It is essential to study the electron beam density profile and the beam center position distribution for optimizing the pseudospark discharge configuration. In this paper, images of some single-shot electron beam pulses have been captured using a 50 μm thickness stopping copper foil and a phosphor screen coated with a P47 scintillator to study the electron beam density profile and the beam center position distribution of the high energy component of the electron beam. The experiments have been carried out on two pseudospark discharge configurations with tw...

Xenon gas field ion source from a single-atom tip.

Abstract: Focused ion beam (FIB) systems have become powerful diagnostic and modification tools for nanoscience and nanotechnology. Gas field ion sources (GFISs) built from atomic-size emitters offer the highest brightness among all ion sources and thus can improve the spatial resolution of FIB systems. Here we show that the Ir/W(111) single-atom tip (SAT) can emit high-brightness Xe+ ion beams with a high current stability. The ion emission current versus extraction voltage was analyzed from 150 K up to 309 K. The optimal emitter temperature for maximum Xe+ ion emission was ~150 K and the reduced brightness at the Xe gas pressure of 1 × 10−4 torr is two to three orders of magnitude higher than that of a Ga liquid metal ion source, and four to five orders of magnitude higher than that of a Xe inductively coupled plasma ion source. Most surprisingly, the SAT emitter remained stable even when operated at 309 K. Even though the ion current decreased with increasing temperature, the current at room temperature (RT) could still reach over 1 pA when the gas pressure was higher than 1 × 10−3 torr, indicating the feasibility of RT-Xe-GFIS for application to FIB systems. The operation temperature of Xe-SAT-GFIS is considerably higher than the cryogenic temperature required for the helium ion microscope (HIM), which offers great technical advantages because only simple or no cooling schemes can be adopted. Thus, Xe-GFIS-FIB would be easy to implement and may become a powerful tool for nanoscale milling and secondary ion mass spectroscopy.

An investigation of the beam damage effect on in situ liquid secondary ion mass spectrometry analysis

Abstract: RATIONALE During in situ liquid SIMS analysis, the primary ion beam was normally scanned on a very small area to collect signals with high ion doses (1014-1016 ions/cm2). As a result, beam damage may become a concern when compared with static limit of SIMS analysis, in which the dose is normally less than 1012 ions/cm2. Therefore, a comparison of ion yields in in situ liquid SIMS analysis versus traditional static SIMS analysis of corresponding dry samples is of great interest. METHODS In this study, a dipalmitoylphosphatidylcholine (DPPC) liposome solution was used as a model system. Both liquid sample and dry sample were examined. Secondary ion yields using three primary ion species (Bi+, Bi3+ and Bi3++) with various beam currents were investigated. RESULTS Usable ion yields for both positive and negative characteristic signals (including molecular ions and characteristic fragment ions) were achievable based on optimized experimental conditions for in situ liquid SIMS analysis. The ion yield of the key DPPC molecular ion was comparable to that of traditional static SIMS, and unexpected low fragmentation was observed. The flexible structure of liquid plays an important role for these observations. CONCLUSIONS Therefore, beam damage may not be a concern in in situ liquid SIMS analysis if proper experimental conditions are used.

Obtaining and doping of InAs-QD/GaAs(001) nanostructures by ion beam sputtering.

Abstract: The features of InAs quantum dots obtained on GaAs(001) single-crystal substrates by ion-beam sputtering were investigated. It has been shown that in the range of ion energies of 150 to 200 eV at a temperature of 500 °C and a beam current of 120 µA InAs quantum dots with average dimensions below 15 nm and a surface density of 1011 cm-2 are formed. The technique of controlled doping of InAs/GaAs nanostructures using a SnTe solid-state source was proposed. It has been established that a maximum donor concentration of 8.7·1018 cm-3 in the GaAs spacer layer is reached at an evaporation temperature of 415 °С. At the same time, impurity accumulation in the growth direction was observed. We have shown that increasing the impurity doping of the GaAs barrier layer increases the intensity of photoluminescence peaks of the ground state and the first excited state of the InAs quantum dots.

Fabrication of nanoscale topographies on Ge(100) surface by low energy Ar + ion sputtering

Abstract: The nanoscale pattern formation on Ge(100) surfaces is studied by exposure of uniform Ar + ion beam of energy 500 eV for ion incidence angle 0°–85° at room temperature. Anisotropic ripple nanopatterns with wave-vector along parallel and perpendicular to the ion beam projection are found to evolve at 75° and 85° respectively for fixed ion fluence 1 × 10 19 cm −2 . In order to explore the ion beam induced ripple formation mechanism, their dynamics with ion fluence at each ion incidence angle of 75° and 85° are also investigated. Perpendicular mode ripples exhibit sawtooth structures and abruptly high surface roughness at larger ion fluences. The overall topographic evolution is discussed in light of existing theoretical models of ion beam nanopatterning.