Showing papers on "Ion beam deposition published in 2012"
TL;DR: It is demonstrated that electrospray ion beam deposition facilitates grafting of intact Mn(12) molecules on metal as well as ultrathin insulating surfaces enabling submolecular resolution imaging by scanning tunneling microscopy.
Abstract: The high intrinsic spin and long spin relaxation time of manganese-12-acetate (Mn12) makes it an archetypical single molecular magnet. While these characteristics have been measured on bulk samples, questions remain whether the magnetic properties replicate themselves in surface supported isolated molecules, a prerequisite for any application. Here we demonstrate that electrospray ion beam deposition facilitates grafting of intact Mn12 molecules on metal as well as ultrathin insulating surfaces enabling submolecular resolution imaging by scanning tunneling microscopy. Using scanning tunneling spectroscopy we detect spin excitations from the magnetic ground state of the molecule at an ultrathin boron nitride decoupling layer. Our results are supported by density functional theory based calculations and establish that individual Mn12 molecules retain their intrinsic spin on a well chosen solid support.
143 citations
Patent•
16 Mar 2012TL;DR: In this paper, a writer main pole for a perpendicular magnetic recording system is provided, which has a tunable bottom gap to side gap ratio, and may be formed using deposition of a first seed layer through an ion beam deposition process, deposition of an intermediate non-magnetic gap layer through a chemical vapor deposition process.
Abstract: A writer main pole for a perpendicular magnetic recording system is provided. The writer pole has a tunable bottom gap to side gap ratio, and may be formed using deposition of a first seed layer through an ion beam deposition process, deposition of a second seed layer through a physical vapor deposition process, and deposition of a non-magnetic gap layer through a chemical vapor deposition process.
130 citations
TL;DR: Raman measurements were carried out to probe the spectroscopic signatures of the ion beam irradiation-induced damage and their in-depth profiles on a Uranium dioxide sample previously cut and polished prior to performing a 25 MeV He2+ cyclotron beam irradiated.
Abstract: Raman measurements were carried out to probe the spectroscopic signatures of the ion beam irradiation-induced damage and their in-depth profiles on a Uranium dioxide sample previously cut and polished prior to performing a 25 MeV He2+ cyclotron beam irradiation. Raman spectra clearly show the creation of three defects bands (U1 ≈ 530, U2 ≈ 575, and U3 ≈ 635 cm−1) resulting from the ion irradiation and also some changes in the T2g peak of UO2. Their in-depth distribution inside the sample exhibits a clear increase of the damage from the surface up to the position of the implanted He.
79 citations
TL;DR: The design, performance parameters, and some applications of a new modified version of this kind of source which is called Mevva-V.Ru are considered, developed at Tomsk and summarized its beam characteristics along with some of the applications to which it is put.
Abstract: Vacuum arc ion sources have been made and used by a large number of research groups around the world over the past twenty years. The first generation of vacuum arc ion sources (dubbed “Mevva,” for metal vapor vacuum arc) was developed at Lawrence Berkeley National Laboratory in the 1980s. This paper considers the design, performance parameters, and some applications of a new modified version of this kind of source which we have called Mevva-V.Ru. The source produces broad beams of metal ions at an extraction voltage of up to 60 kV and a time-averaged ion beam current in the milliampere range. Here, we describe the Mevva-V.Ru vacuum arc ion source that we have developed at Tomsk and summarize its beam characteristics along with some of the applications to which we have put it. We also describe the source performance using compound cathodes.
69 citations
TL;DR: It is demonstrated that for ultrashort (pulse duration ~30 fs) highly relativistic laser pulses, the intra-pulse phase of the proton acceleration process becomes relevant, yielding maximum energies of around 20 MeV.
Abstract: High-intensity laser plasma-based ion accelerators provide unsurpassed field gradients in the megavolt-per-micrometer range. They represent promising candidates for next-generation applications such as ion beam cancer therapy in compact facilities. The weak scaling of maximum ion energies with the square-root of the laser intensity, established for large sub-picosecond class laser systems, motivates the search for more efficient acceleration processes. Here we demonstrate that for ultrashort (pulse duration ~30 fs) highly relativistic (intensity ~10(21) W cm(-2)) laser pulses, the intra-pulse phase of the proton acceleration process becomes relevant, yielding maximum energies of around 20 MeV. Prominent non-target-normal emission of energetic protons, reflecting an engineered asymmetry in the field distribution of promptly accelerated electrons, is used to identify this pre-thermal phase of the acceleration. The relevant timescale reveals the underlying physics leading to the near-linear intensity scaling observed for 100 TW class table-top laser systems.
67 citations
TL;DR: The motivation for a neon gas field ion source, the expected performance through simulations, and the update of the experimental progress are outlined.
Abstract: Summary
The success of the helium ion microscope has encouraged extensions of this technology to produce beams of other ion species. A review of the various candidate ion beams and their technical prospects suggest that a neon beam might be the most readily achieved. Such a neon beam would provide a sputtering yield that exceeds helium by an order of magnitude while still offering a theoretical probe size less than 1-nm. This article outlines the motivation for a neon gas field ion source, the expected performance through simulations, and provides an update of our experimental progress. SCANNING 33: 129–134, 2012. © 2011 Wiley Periodicals, Inc.
67 citations
TL;DR: A pulsed ion-beam method is used to measure a characteristic time constant of dominant dynamic annealing processes of about 6 ms in Si bombarded at room temperature with 500 keV Ar ions.
Abstract: Under ion irradiation, all crystalline materials display some degree of dynamic annealing when defects experience evolution after the thermalization of collision cascades. The exact time scales of such defect relaxation processes are, however, unknown even for Si at room temperature. Here, we use a pulsed ion-beam method to measure a characteristic time constant of dominant dynamic annealing processes of about 6 ms in Si bombarded at room temperature with 500 keV Ar ions.
38 citations
37 citations
TL;DR: In this article, the EAST-NBI system was developed successfully on schedule and achieved a high power ion beam of 3 MW with 80 keV beam energy in 0.5 s beam duration.
Abstract: The neutral beam injection (NBI) system is one of the most important auxiliary plasma heating and current driving methods for fusion device. A high power ion beam of 3 MW with 80 keV beam energy in 0.5 s beam duration and a long pulse ion beam of 4 s with 50 keV beam energy ion beam extraction were achieved on the EAST neutral beam injector on the test-stand. The preliminary results show that the EAST-NBI system was developed successfully on schedule.
36 citations
TL;DR: In this article, full particle particle-in-cell simulations are performed to study the collisionless electron-ion coupling during ion beam emission and neutralization, and it is shown that ion beam neutralization and propagation are two closely coupled processes.
Abstract: Full particle particle-in-cell simulations are performed to study the collisionless electron-ion coupling during ion beam emission and neutralization. Simulations show that ion beam neutralization and propagation are two closely coupled processes. Electron-ion coupling is achieved through interactions between the trapped electrons and a potential well established by the propagation of the ion beam front along the beam direction and not through plasma instabilities as previous studies suggested. In the transverse direction, the beam emission generates an expansion fan similar to that of the expansion of a mesothermal plasma into vacuum. The expansion process determines the beam potential with respect to the ambient. This suggests that a plasma beam in a vacuum chamber and a plasma beam in space may have similar charge density profiles but different beam potentials with respect to the ambient due to the limit imposed by the boundary on plasma expansion.
36 citations
TL;DR: In this article, diamond-like carbon (DLC) and N-doped DLC thin films have been synthesized on polytetrafluroethylene (PTFE) and silicon wafers using ion beam deposition.
TL;DR: In this paper, negative ion energy and flux entering the substrate were quantitatively measured and compared with the preferential crystalline growth of unusual (112¯0) orientation in ZnO films.
Abstract: A polycrystalline film usually grows in its most densely packed plane parallel to the substrate plane. We demonstrated that the unusual crystalline growth can occur by using energetic negative ions generated in the magnetron capacitively coupled plasma deposition without using separated ion source. Negative ion energy and flux entering the substrate were quantitatively measured and compared with the preferential crystalline growth of unusual (112¯0) orientation in ZnO films. Strong (112¯0) orientation was found at the cathode erosion area where large amount of high energy negative ion of 170–250 eV was observed in low gas pressure of 0.1 Pa.
Patent•
21 Mar 2012TL;DR: In this paper, an ion implantation method includes reciprocally scanning an ion beam, mechanically scanning a wafer in a direction perpendicular to the ion beam scanning direction, implanting ions into the wafer, and generating an ion insertion amount distribution in an isotropic concentric circle shape.
Abstract: An ion implantation method includes reciprocally scanning an ion beam, mechanically scanning a wafer in a direction perpendicular to the ion beam scanning direction, implanting ions into the wafer, and generating an ion implantation amount distribution in a wafer surface of an isotropic concentric circle shape for correcting non-uniformity in the wafer surface in other semiconductor manufacturing processes, by controlling a beam scanning speed in the ion beam scanning direction and a wafer scanning speed in the mechanical scanning direction at the same time and independently using the respective control functions defining speed correction amounts
TL;DR: In this article, a low-energy ion beam modification was proposed to create graphene on the top of the insulated diamond-like carbon (DLC) films, which showed partial crystallization and were similar to the spectra of defected graphene.
TL;DR: In this paper, the authors demonstrated that nanohole pattern formation is independent of ion flux over several orders of magnitude and scanning of a focused ion beam under appropriate conditions is identical to broad ion beam irradiation.
Abstract: Hexagonally ordered nanohole patterns were produced on Ge(100) surfaces by focused Ga+ ion beam and broad Ga+ ion beam irradiations with 5 keV energy under normal incidence. Identical patterns were obtained by irradiations with a scanning focused ion beam under different irradiation conditions and with a broad Ga+ beam without scanning and five orders of magnitude smaller ion flux. Thus, we could demonstrate that nanohole pattern formation is independent of ion flux over several orders of magnitude and scanning of a focused ion beam under appropriate conditions is identical to broad ion beam irradiation.
TL;DR: Penning ion source performance for neutron generator applications is characterized by the atomic ion fraction and beam current density, providing two paths by which source performance can be improved for increased neutron yields.
Abstract: Penning ion source performance for neutron generator applications is characterized by the atomic ion fraction and beam current density, providing two paths by which source performance can be improved for increased neutron yields. We have fabricated a Penning ion source to investigate novel methods for improving source performance, including optimization of wall materials and electrode geometry, advanced magnetic confinement, and integration of field emitter arrays for electron injection. Effects of several electrode geometries on discharge characteristics and extracted ion current were studied. Additional magnetic confinement resulted in a factor of two increase in beam current density. First results indicate unchanged proton fraction and increased beam current density due to electron injection from carbon nanofiber arrays.
TL;DR: This work fabricated and measured single domain wall magnetoresistance devices with sub-20 nm gap widths using a novel combination of electron beam lithography and helium ion beam milling, and indicates that sub-5 nm constriction widths could be possible.
Abstract: We have fabricated and measured single domain wall magnetoresistance devices with sub-20 nm gap widths using a novel combination of electron beam lithography and helium ion beam milling. The measurement wires and external profile of the spin valve are fabricated by electron beam lithography and lift-off. The critical bridge structure is created using helium ion beam milling, enabling the formation of a thinner gap (and so a narrower domain wall) than that which is possible with electron beam techniques alone. Four-point probe resistance measurements and scanning electron microscopy are used to characterize the milled structures and optimize the He ion dose. Successful operation of the device as a spin valve is demonstrated, with a 0.2% resistance change as the external magnetic field is cycled. The helium ion beam milling efficiency as extracted from electrical resistance measurements is 0.044 atoms/ion, about half the theoretical value. The gap in the device is limited to a maximum of 20 nm with this technique due to sub-surface swelling caused by injected ions which can induce catastrophic failure in the device. The fine patterning capabilities of the helium ion microscope milling technique indicate that sub-5 nm constriction widths could be possible.
TL;DR: In this paper, it was shown by the 2D particle in cell simulation that the H− ions extracted from the periphery of the meniscus cause a beam halo since the surface produced H− ion penetrate into the bulk plasma, and thus the resultant menisus has a relatively large curvature.
Abstract: A meniscus of plasma-beam boundary in H− ion sources largely affects the extracted H− ion beam optics. Although it is hypothesized that the shape of the meniscus is one of the main reasons for the beam halo observed in experiments, a physical mechanism of the beam halo formation is not yet fully understood. In this letter, it is first shown by the 2D particle in cell simulation that the H− ions extracted from the periphery of the meniscus cause a beam halo since the surface produced H− ions penetrate into the bulk plasma, and, thus, the resultant meniscus has a relatively large curvature.
TL;DR: Crystalline inverted membranes of the nonvolatile surfactant sodium dodecylsulfate are found on solid surfaces after electrospray ion beam deposition (ES-IBD) of large SDS clusters in vacuum, demonstrating the equivalence of ES- IBD to conventional molecular beam epitaxy.
Abstract: Crystalline inverted membranes of the nonvolatile surfactant sodium dodecylsulfate are found on solid surfaces after electrospray ion beam deposition (ES-IBD) of large SDS clusters in vacuum. This demonstrates the equivalence of ES-IBD to conventional molecular beam epitaxy.
04 Apr 2012
TL;DR: In this article, the acceleration of positive ions to a few tens of eV by the plasma potential difference between the driver and the extraction regions can have an important effect on negative ion production by enhancing the negative ion yield from caesiated surfaces, and by charge exchange reactions with caesium atoms.
Abstract: A brief description is given of the basic processes in negative ion sources dedicated to fusion. It is considered that in these sources negative ions are produced by ions and atoms interacting with a caesiated surface, but this mechanism is not unique: the volume production, based on dissociative electron attachment to rovibrationally excited molecules, is also active. We suggest that in RF sources the acceleration of positive ions to a few tens of eV by the plasma potential difference between the driver and the extraction regions can have an important effect on negative ion production by enhancing the negative ion yield from caesiated surfaces, and by charge exchange reactions with caesium atoms. The presence of energetic positive ions can have other implications (modifying the virtual cathode in front of the plasma grid, participating in caesium ionization).
TL;DR: The reaction kinetics of ion-ion-recombination is investigated to establish selective ion suppression as an easy to apply separation technique for otherwise non-selective ion detectors.
Abstract: For future development of simple miniaturized sensors based on pulsed atmospheric pressure ionization as known from ion mobility spectrometry, we investigated the reaction kinetics of ion–ion-recombination to establish selective ion suppression as an easy to apply separation technique for otherwise non-selective ion detectors. Therefore, the recombination rates of different positive ion species, such as protonated water clusters H+(H2O)n (positive reactant ions), acetone, ammonia and dimethyl-methylphosphonate ions, all recombining with negative oxygen clusters O2−(H2O)n (negative reactant ions) in a field-free reaction region, are measured and compared. For all experiments, we use a drift tube ion mobility spectrometer equipped with a non-radioactive electron gun for pulsed atmospheric pressure ionization of the analytes. Both, ionization and recombination times are controlled by the duty cycle and repetition rate of the electron emission from the electron gun. Thus, it is possible to investigate the ion loss caused by ion–ion-recombination depending on the recombination time defined as the time delay between the end of the electron emission and the ion injection into the drift tube. Furthermore, the effect of the initial total ion density in the reaction region on the ion–ion-recombination rate is investigated by varying the density of the emitted electrons.
TL;DR: In this paper, the authors studied the impact of light inert helium ions on deposition rate and structure purity, with some implications on the usefulness of HIM nano-machining for circuit modification.
Abstract: In this paper we studied helium ion beam induced deposition (HIBID) of Pt on a silicon wafer using the recently commercialized helium ion microscope (HIM) at 25 kV and low beam currents. The motivation of this work was to understand the impact of light, inert helium ions on deposition rate and structure purity, with some implications on the usefulness of HIM nano-machining for circuit modification. Two Pt-rich deposits with sub-micron dimensions were grown with HIBID at different ion beam currents. The pillar and substrate structure were studied using bright and dark field TEM images. The authors analyzed metal purity profile of the HIBID deposit on height using energy dispersive x-ray spectroscopy. The maximum Pt content measured reached 41%, which is the highest measured metal content of a HIBID-grown structure. TEM studies of the sub-surface damage to the Si shows more damage below the deposit grown at a higher beam current. The differences in amorphization layer thickness between the two different beam currents are discussed. A comparison to Pt deposition by Ga FIB and electron beam induced deposition is provided, along with conclusions regarding the usage of HIBID technology for circuit modification. © 2012 American Vacuum Society.
TL;DR: In this paper, the effect of substrate temperature on micro-structural properties of ZnO thin films prepared by ion beam deposition technique was investigated, and the structural properties and surface morphologies were examined by high resolution X-ray diffraction and field emission scanning electron microscopy, respectively.
Abstract: We have investigated the effect of substrate temperature on micro-structural properties of ZnO thin films prepared by ion beam deposition technique. ZnO thin films were deposited on AlN-buffered Si (111) and sapphire (001) substrates at various substrate temperatures. The structural properties and surface morphologies were examined by high resolution X-ray diffraction (XRD) and field emission scanning electron microscopy, respectively. The RMS roughness was measured by atomic force microscopy. XRD measurements confirmed that the ZnO thin films were grown well on the AlN-buffered Si (111) and sapphire (001) substrates along the c-axis. Minimization of residual stress was carried out by tuning the substrate temperature. The structural properties were notably improved with increasing substrate temperature.
TL;DR: The chemical degradation caused by local beam heating is found to be significantly reduced by cooling the specimen to −25°C during milling, consistent with observations that reversible and repeatable thermal actuation of a fabricated polystyrene–platinum microcantilevers is only observed when the cantilever is prepared at low temperature milling.
Abstract: Summary
Focused ion beam micromachining provides a maskless and resistless technique for prototyping of structures from thermoplastic polymers, an example being the production of polystyrene microcantilevers with potential applications as micro/nanoelectromechanical systems sensors and actuators. The applicability of FIB technology is, however, often restricted by the damage created by high energy gallium ion bombardment and local beam heating, which can affect the desired properties and limit the minimum achievable size of the fabricated structure. To investigate the ion-induced damage and determine the limitations of the technique for polymer nanofabrication, we have exposed thin polystyrene film to the ion beam at varying ion doses, ion energies and specimen temperatures. Ion doses ranging from 1016 to 1018 ions cm−2 show significant gallium implantation, redeposition of sputtered material and chemical degradation in the polymer. Raman results show that the local heating in polymer during milling is severe at room temperature, damaging the aromatic carbon bonding (C = C) in particular. These observations are supported by the results of a beam heating model and Monte Carlo simulations. The chemical degradation caused by local beam heating is found to be significantly reduced by cooling the specimen to −25°C during milling. This is consistent with observations that reversible and repeatable thermal actuation of a fabricated polystyrene–platinum microcantilever is only observed when the cantilever is prepared at low temperature milling. Using this cooling approach, polymer structures can be fabricated with dimensions as low as 200 nm and still retain a sufficient volume of material unaffected by the ion beam.
TL;DR: In this paper, the preliminary data of ion beam extraction was obtained on the EAST neutral beam injector test-stand, by measuring the beam current with a Faraday cup and by analyzing the results obtained by means of water calorimetric measurement on the temperature rises of water cooling the accelerator electrodes.
Abstract: Neutral beam injection is recognized as one of the most effective means for plasma heating. The preliminary data of ion beam extraction is obtained on the EAST neutral beam injector test-stand. Beam extraction from the ion source of EAST-NBI is verified by measuring the beam current with a Faraday cup and by analyzing the results obtained by means of water calorimetric measurement on the temperature rises of water cooling the accelerator electrodes.
TL;DR: In this article, the results obtained from Langmuir probe and retarding field energy analyzer diagnostics operated in the plasma plume of the APS are presented, where the source was operated with argon.
Abstract: The Advanced Plasma Source (APS) is employed for plasma ion-assisted deposition (PIAD) of optical coatings. The APS is a hot cathode dc glow discharge which emits a plasma ion beam to the deposition chamber at high vacuum (p 2 × 10−4 mbar). It is established as an industrial tool but to date no detailed information is available on plasma parameters in the process chamber. As a consequence, the details of the generation of the plasma ion beam and the reasons for variations of the properties of the deposited films are barely understood. In this paper the results obtained from Langmuir probe and retarding field energy analyzer diagnostics operated in the plasma plume of the APS are presented, where the source was operated with argon. With increasing distance to the source exit the electron density (ne) is found to drop by two orders of magnitude and the effective electron temperature (Te,eff) drops by a factor of five. The parameters close to the source region read ne 1011 cm−3 and Te,eff 10 eV. The electron distribution function exhibits a concave shape and can be described in the framework of the non-local approximation. It is revealed that an energetic ion population leaves the source region and a cold ion population in the plume is build up by charge exchange collisions with the background neutral gas. Based on the experimental data a scaling law for ion beam power is deduced, which links the control parameters of the source to the plasma parameters in the process chamber.
Patent•
19 Jun 2012TL;DR: In this paper, a tandem mass spectrometer and method for the generation of precursors is described, where a single pass ion page (40) in the path of the precursor ions between the ion injector (21, 23) and the ion guide (50, 60) is controlled so that (only a subset of precursor ion packets, containing precursor ions of interest, is allowed onward transmission to the ion guidance (50 and 60).
Abstract: A tandem mass spectrometer and method are described. Precursor ions are generated in an ion source (10) and an ion injector (21, 23) injects ions towards a downstream ion guide (50, 60) via a single or multi reflection TOF device (30) that separates ions into packets in accordance with their m/z. A single pass ion page (40) in the path of the precursor ions between the ion injector (21, 23) and the ion guide (50, 60) is controlled so that (only a subset of precursor ion packets, containing precursor ions of interest, is allowed onward transmission to the ion guide (50, 60). A high resolution mass spectrometer (70) is provided for analysis of those ions, or their fragments, which have been allowed passage through the ion gate (40). The technique permits multiple m/z ranges to be selected from a wise mass range of precursors, with optional fragmentation of one or more of the chosen ion species.
TL;DR: The results show that the thickness of the amorphous surface layer can be successfully reduced below 1 nm by low energy ion milling, leading to a homogeneous image contrast in TEM and STEM, so that good conditions for quantitative analysis can be achieved.
TL;DR: In this article, the ability to effectively control ion trajectories and spatially manipulate ions without the use of vacuum systems is of great interest in a number of different fields, such as robotics and artificial intelligence.
TL;DR: In this paper, the influence of tungsten incorporation on the microstructure, surface topography, mechanical and tribological properties of the DLC were studied using X-ray photoelectron spectroscopy (XPS), Raman spectroscope.