Ar Ion Beam Research Articles

Ion beam figuring with focused anode layer thruster.

This work presents the peculiarities of cone ion beam formation with a focused thruster with anode layer (TAL) and its application to silicon carbide (SiC) ion beam figuring. Modeling results of Lorentz E × B force distribution in the discharge gap are presented. 3D particle tracing for keV Ar ions is carried out for the first time in the beam drift region of TAL with magnetic lens. Extracted ion beam full width at half maxima is about 2mm in the focal plane, where the SiC etching rate reaches 0.5 µm/min. The SiC sputter yields are measured as a function of the Ar ion impact energy and beam incidence angle. The maximum sputter yield of 2.8 atom/ion is observed at 45° of the beam-sample angle for the Si targets. Furthermore, the maximum sputter yield value of 1.7 atom/ion is measured at 30° of the beam-sample angle for the SiC targets. The novelty of present research is in the application of focused TAL keV Ar ion beam to the SiC ion beam figuring.

Effect of specimen processing for transmission electron microscopy on lattice spacing variation in Si specimens

Variation in the (220) lattice spacing of Si due to specimen processing for transmission electron microscopy (TEM) was experimentally evaluated by comparing the measured lattice spacings of crystalline specimens processed by crushing, mechanical polishing only, and combined mechanical and Ar ion polishing. Although distinct variation in the (220) lattice spacing between the Si specimens processed by crushing and by mechanical polishing only is not observed, the (220) lattice spacing of specimens prepared by combined mechanical and Ar ion polishing imply increasing tendency with increasing Ar ion beam irradiation time. Moreover, the (220) lattice spacing measured from the outermost region of the specimen edge tends to be approximately 3% to 5% larger than that measured from the inner region, irrespective of the processing method. These results demonstrate that differences in the processing conditions of Si specimens and in the measurement location of the Si lattice spacing can be major component of the measurement uncertainty in sub-nanometer metrology using TEM with magnification calibration by the Si lattice spacing. When attempting to apply the lattice spacing of Si as a reference with traceability to the International System of Units for TEM magnification calibration in sub-nanometer metrology, the results suggest that the effect of specimen processing on variation in the lattice spacing is not negligible.

Surface microstructure and wetting of SiC ceramic modified by ion bombardment

Ion bombardment is one of the powerful methods to modify the surface characteristics of materials. In this study, SiC ceramic is bombarded under different fluences by 60 keV Ar-ion beam. The effects of Ar ion bombardment on the surface microstructure and subsequent wetting of SiC ceramic using AgCu-Ti filler metal are investigated. Ar ion bombardment can break the SiC bond of SiC cell, thus, SiCx(x < 1), SiCx(x < 1) twins and the amorphous layer are generated in the SiC surface with the increase of fluence from 1×1014/cm2 to 1×1017/cm2. With the increase of fluences, the contact angle decreases by the acceleration of interfacial reaction rate as a result of the break of SiC bond in SiC surface in the rapid spreading stage. The amorphous layer is gradually formed in the SiC surface, requiring more time to reach the equilibrium stage for droplets, while the bonding quality of the SiC/AgCu-Ti wetting interface is obviously improved. Significant modification in the microstructural and excellent wetting behavior are obtained by leveraging the ion bombardment technique.

Microfabrication of Si by KOH Etchant Using Etching Mask Amorphized by Ar Ion Beam

Microfabrication of Si by KOH Etchant Using Etching Mask Amorphized by Ar Ion Beam

Advanced scanning electron microscopy techniques for structural characterization of zeolites

Chemical etching after Ar ion beam cross sectioning enables the formation of zeolite internal nano structures to be observed directly using a newly developed highly sensitive scanning electron microscope.

Impact of ion beam irradiation on two-dimensional MoS2: a molecular dynamics simulation study

Two-dimensional (2D) materials such as MoS2 have extraordinary properties and significant application potential in electronics, optoelectronics, energy storage, bioengineering, etc. To realize the numerous application potential, it is needed to modulate the structure and properties of these 2D materials, for which ion beam irradiation has obvious advantages. This research adopted classical molecular dynamics simulations to study the sputtering of atoms in 2D MoS2, defect formation and the control rule under Ar ion beam irradiation, considering the influence of ion irradiation parameters (i.e., ion beam energy, ion dose), layer number of 2D MoS2, substrate. Furthermore, the uniaxial mechanical performance of the ion-irradiated nanostructures was investigated for actual applications loading with mechanical stress/strain. This research could provide important theoretical support for fabricating high-performance 2D MoS2-based nanodevices by ion beam irradiation method.

Understanding the role of structural distortions on the transport properties of Ar ion irradiated SrTiO3 thin films: X-ray absorption investigation

We report the evolution of structural distortions on the pulsed laser deposited SrTiO3 (STO) thin films irradiated by 1 MeV Ar ion beam and their response in the electrical and thermoelectric properties correlated with their electronic structures. The structural studies reveal a modification in the crystalline nature resulting in the synergistic enhancement of resistivity and the Seebeck coefficient due to ion irradiation-induced oxygen vacancies and augment the power factor to ∼17 μW m−1K−2, which is 2.5 times higher than the pristine STO. An in-depth analysis of the conduction mechanism using various theoretical models implies the role of band conduction and Mott-variable range hopping. Further, the changes in the local electronic structures are reflected in the variation in the Ti–O bond length and the density of unoccupied states that alter the spectral intensities and chemical shifts and are responsible for the observed enhancement in the thermoelectric properties. The above results indicate the significance of the ion beams to tune the electrical and thermoelectric properties.

Impact of ion species on ion beam sputtered Ta2O5 layer quality parameters and on corresponding process productivity: A preinvestigation for large-area coatings

The demand for ion beam sputtering-coated substrates is growing. In order to introduce ion beam sputter deposition (IBSD) technology into new fields of application, the deposition area must be further increased. In this context, the ion species applied for the sputtering process is an important parameter. In the present investigation, an industrial scale IBSD process was characterized with respect to productivity and layer quality by varying the ion species. Ar, Kr, or Xe broad ion beams at an ion energy of 1.8 keV were used, and the evaluation was carried out on the basis of Ta2O5 layers. The dielectric films were produced in a reactive process through the sputtering of a metallic Ta target, and their two-dimensional distributions of the coating rate R, the refractive index n(320nm), and the extinction coefficient k(320nm) were determined over a planar area of 0.9 × 1.0 m2 above the target by the collection method. R served as a measure of productivity, while n(320nm) and k(320nm) were quality parameters. Additionally, the layer composition was determined for selected samples on the collector by an electron probe microanalyzer (EPMA). As expected, the different ion-solid interaction mechanisms resulted in significant differences with regard to productivity. Linear scaling of productivity as a function of ion mass was observed. Calculations of the sputtering yield with semiempirical models or SRIM-2013, a binary collision Monte Carlo simulation program, did not confirm the observed linearity. Furthermore, the configuration with the highest productivity, Xe, led to a locally occurring and significant reduction in layer quality, more precisely, an increase of k(320nm). Additionally, the layer compositions determined with EPMA confirmed that ions originating from the ion source were implanted in the thin films during their formation. A detailed evaluation of the angle-resolved energy distributions of the involved particles, simulated with SRIM-2013, was performed. However, the determination of the energies carried away from the target by backscattered ions and sputtered target atoms does not explain the observed degradation mechanism. This concludes that for the realization of future large-area coatings with IBSD, not all relevant mechanisms are yet understood in sufficient detail.

Identification and characterization of inheritable structural variations induced by ion beam radiations in rice.

High energy ion beams are effective physical mutagens for mutation induction in plants. Due to their high linear energy transfer (LET) property, they are known to generate single nucleotide variations (SNVs) and insertion/deletions (InDels, <50 bp) as well as structural variations (SVs). However, due to the technical difficulties to identify SVs, studies on ion beam induced SVs by genome sequencing have so far been limited in numbers and inadequate in nature, and knowledge of SVs is scarce with regards to their characteristics. In the present study, we identified and validated SVs in six M4 plants (designated as Ar_50, Ar_100, C_150, C_200, Ne_50 and Ne_100 according to ion beam types and irradiation doses), two each induced by argon (40Ar18+), carbon (12C6+) and neon (20Ne10+) ion beams and performed in depth analyses of their characteristics. In total, 22 SVs were identified and validated, consisting of 11 deletions, 1 duplication, and 4 intra-chromosomal and 6 inter-chromosomal translocations. There were several SVs larger than 1 kbp. The SVs were distributed across the whole genome with an aggregation with SNVs and InDels only in the Ne_50 mutants. An enrichment of a 11-bp wide G-rich DNA motif 'GAAGGWGGRGG' was identified around the SV breakpoints. Three mechanisms might be involved in the SV formation, i.e., the expansion of tandem repeats, transposable element insertion, and non-allelic homologous recombination. Put together, the present study provides a preliminary view of SVs induced by Ar, C and Ne ion beam radiations, and as a pilot study, it contributes to our understanding of how SVs might form after ion beam irradiation in rice.

New approach for fabrication of annealing-free ferroelectric HfO2-based films at room temperature

In this work, ferroelectric properties with a coercive field of 1.6 MV/cm and a remanent polarization of 17.9 μC/cm2 were achieved in Y-doped HfO2 thin films prepared by ion beam assisted RF magnetron sputtering without any heating and annealing. Systematic grazing incidence X-ray diffraction and polarization hysteresis measurements revealed that the structural and electrical properties of the films were strongly dependent on the applied ion beam energy. A model of phase transition kinetics during deposition was introduced to explain the variations in the crystal structure and electric properties with various ion beam energies. It was found that the bombardment of the Ar ion beam provided extra energy to the sputtering particles, therefore conducive to the increased atomic diffusion and overcoming the potential barriers of the phase transition. The current processing method provides great potential for ferroelectric device applications that cannot be addressed with heating and annealing.

Preliminary Validation of a Continuum Model for Dimple Patterns on Polyethylene Naphthalate via Ar Ion Beam Sputtering.

This work reports the self-organization of dimple nanostructures on a polyethylene naphthalate (PEN) surface where an Ar ion beam was irradiated at an ion energy of 600 eV. The peak-to-peak roughness and diameter of dimple nanostructures were 29.1~53.4 nm and 63.4~77.6 nm, respectively. The electron energy loss spectrum at the peaks and troughs of dimples showed similar C=C, C=O, and O=CH bonding statuses. In addition, wide-angle X-ray scattering showed that Ar ion beam irradiation did not induce crystallization of the PEN surface. That meant that the self-organization on the PEN surface could be due to the ion-induced surface instability of the amorphous layer and not due to the partial crystallinity differences of the peaks and valleys. A nonlinear continuum model described surface instability due to Ar ion-induced sputtering. The Kuramoto–Sivashinsky model reproduced the dimple morphologies numerically, which was similar to the experimentally observed dimple patterns. This preliminary validation showed the possibility that the continuum equation used for metal and semiconductor surfaces could be applied to polymer surfaces where ion beam sputtering occurred.

Microwave-accessibility conditions estimated by plasma parameters obtained experimentally on electron cyclotron resonance ion source.

We insert two probes in the upstream and the downstream regions with respect to the electron cyclotron resonance (ECR) zone which is formed at the center of mirror fields. We measure simultaneously plasma parameters in those regions by each of them under the same operating condition. We measure ion saturation currents Iis and electron energy distribution functions at two positions. We obtain measurement results that suggest the more efficient ECR on the side closer to the microwave-launchings than those on the other side. It is consistent with the accessibility condition of the right-hand polarization wave. We also compare the charge state distributions of Ar ion beams extracted in the case of launching microwaves from the coaxial semi-dipole antenna and those from the rod antenna. We observe the higher multicharged ion beam currents at the low microwave powers in the case of the rod antenna than those in the case of the coaxial semi-dipole antenna. We also confirm stable increasements of ion beam currents at considerably high microwave powers in the case of the coaxial semi-dipole antenna. Based on the experimental results, we propose a new microwave-launching method, "dual-ECR heating" and report its preferable preliminary experimental results in this paper.

Properties of indium tin oxide thin films grown by Ar ion beam sputter deposition

Indium tin oxide (ITO) thin films were grown by Ar ion beam sputter deposition under systematic variation of ion energy, geometrical parameters, and O2 background pressure and characterized with regard to the film thickness, growth rate, crystalline structure, surface roughness, mass density, composition, electrical, and optical properties. The growth rate shows an over-cosine, forward-tilted angular distribution with a maximum, which increases with increasing ion energy, increasing ion incidence angle, and decreasing O2 background pressure. ITO films were found to be amorphous with a surface roughness of less than 1 nm. Mass density and composition show only small changes with increasing scattering angle. The electrical resistivity behavior in dependence on the process parameters is complex. It is not only driven by the O2 background pressure but also very much by the scattering angle. The observed behavior can be understood only if competing processes are considered: (i) reduction of the number of oxygen vacancies due to the presence of O2 background gas and (ii) defect generation and preferential sputtering of oxygen at the surface of the growing films due to the impact of high-energy scattered particles. Even though absolute numbers differ, optical characterization suggests a similar systematics.

Tuning the optical and electrical properties of magnetron-sputtered Cu–ZnO thin films using low energy Ar ion irradiation

Cu doped ZnO (Cu–ZnO) nanocomposite thin films were successfully synthesized at room temperature by RF magnetron sputtering. The signature of Cu in pristine ZnO thin films was confirmed by Rutherford Backscattering Spectroscopy (RBS) with atomic concentration of ~10%. The Cu–ZnO thin films were irradiated with 800 keV Ar ion beam at three different ion fluences viz. 5 × 1015, 7 × 1015 and 9 × 1015 ions/cm2. As characterized by X-ray diffraction, the pristine and irradiated films show a hexagonal wurtzite structure with remarkable intensities of (100), (002) and (101) orientations. The surface morphology of the pristine and irradiated films was recorded using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The images clearly show the grain growth near the surface of films with increasing the ion fluences. The surface plasmon absorption (380 nm onwards) indicating the formation of metal nanoparticles in oxide matrices was confirmed by UV–visible spectroscopy of ion irradiated films. The electrical properties of the pristine and irradiated films were deduced by current voltage (I–V) and Hall measurements. The conductivity of the film increases as irradiation proceeds, achieves a maxima and then decreases with further processing of the ion beam. This study explores ion beam irradiation as a versatile tool to tailor the physical properties of nanocomposite thin films. Further, the properties can be precisely controlled by optimizing ion fluences and incident ion energy as well.

Extraction and transport of low-energy Ar ion beams with a broad cross-section

Low-energy argon (Ar) ion beams were accelerated from a quiescent discharge in a custom-designed ion reservoir. Around 100 eV Ar ion beams were extracted from an ion source with different multi-cusp magnetic field configurations through a 4-cm diameter two-electrode extraction system. Langmuir probe measurements correlated the source plasma characteristics to the extracted ion beam properties that were determined using a retarding potential analyzer and a moving Faraday cup. The ion extractor configuration allowed primary electrons from the ion reservoir to seep downstream to neutralize the space-charge of the Ar ions. The broad cross-section ion beam system is designed for material synthesis and surface modification.

Room Temperature Wafer Bonding of Glass Using Aluminum Oxide Intermediate Layer

AbstractThis paper presents a room temperature bonding technique of glass substrates with a transparent bonding interface. As a room temperature bonding method, surface activated bonding (SAB) is applied for the bonding of glass using Si intermediate layer. However, the bonding interface is colored by the deposited Si layers, which leads to lower applicability to optical devices. In this study, a new concept of SAB is developed using aluminum oxide intermediate layer. Glass substrates are successfully bonded at room temperature via the aluminum oxide intermediate layers activated by Ar ion beam irradiation, showing a bond strength of 1.32 J m−2. It is also shown that the optical characteristics at the interface such as transparency and reflectance are not degraded, while the bonding interface of the SAB using Si intermediate layer deteriorates. The XPS and STEM‐EDX analyses indicate that the bonding is achieved through the amorphous and O‐deficient aluminum oxide interface. This technique will provide a transparent interface for glass bonding by a room temperature process, which is highly desired in optical device fabrication.

Sharpening of the diamond tool edge by the Ar ion beam machine tool

Sharpening of the edge on the single crystal diamond cutting tool by Ar ion beam machine tool is discussed. The cutting edge of the diamond tool can be sharpened by the ion plasma because an etching rate is changed by changing the beam irradiation angle on the machining surface. Machining experiments were carried out to observe the effect of the beam irradiation direction on etching characteristics. In these experiments, a single point flat tool is fabricated to the micro scale structure by Focused Ion Beam (FIB) machine tool on its cutting edge to make the edge roundness artificially. Then, the argon ion beam produced by the penning ion sources irradiated on the rounded edge in various direction. In machining tests, it was observed that the shape of edge was not only sharpened, but also made to be the flat as the new rake face on its rounded face by specific inclination of the beam irradiation. Based on this result, the machining was performed by changing the beam irradiation direction additionally. As the result, it is observed that the new flat face is fabricated according to the intended direction.

Complementary sample preparation strategies (PVD/BEXP) combining with multifunctional SPM for the characterizations of battery interfacial properties

The cathode/anode-electrolyte interfaces in lithium/sodium ion batteries act as the “gate” for the ion exchange between the solid electrode and liquid electrolyte. Understanding the interfacial properties of these solid-liquid interfaces is essential for better design high-performance lithium/sodium ion batteries. Here, we provide a novel method for studying solid-liquid interfacial properties of battery materials through combining physical vapor deposition (PVD) and beam-exit cross-sectional polishing (BEXP) followed by controlled environment multifunctional Scanning Probe Microscope (SPM). In this method, commercial battery materials can be either directly grown on the current collector substrates, or polished by obliqued Ar-ion beams to get a nanoscale flat surface which allows the multifunctional SPM to study sample directly in the liquid electrolyte or in protective oxygen/H2O free environment. This approach allows to investigate wide range of interfacial properties, including surface morphology, internal cracks, mechanical properties, electronic/ionic conductivity and surface potential, with nanoscale resolution in-operando during the battery cycles as well as post-mortem.•PVD and novel BEXP methods were introduced to prepare battery powder materials as perfect specimens for nanoscale SPM characterization.•Various physical/chemical properties of battery materials can be probed on the as-prepared specimens under liquid electrolyte using in situ/operando SPM techniques.•Ex situ/post-mortem analyses based on the controlled environment multifunction SPM characterizations can be achieved in the BEXP polished degradation battery electrodes.

Laser Printing of Plasmonic Nanosponges.

Three-dimensional porous nanostructures made of noble metals represent novel class of nanomaterials promising for nonlinear nanooptics and sensors. Such nanostructures are typically fabricated using either reproducible yet time-consuming and costly multi-step lithography protocols or less reproducible chemical synthesis that involve liquid processing with toxic compounds. Here, we combined scalable nanosecond-laser ablation with advanced engineering of the chemical composition of thin substrate-supported Au films to produce nanobumps containing multiple nanopores inside. Most of the nanopores hidden beneath the nanobump surface can be further uncapped using gentle etching of the nanobumps by an Ar-ion beam to form functional 3D plasmonic nanosponges. The nanopores 10–150 nm in diameter were found to appear via laser-induced explosive evaporation/boiling and coalescence of the randomly arranged nucleation sites formed by nitrogen-rich areas of the Au films. Density of the nanopores can be controlled by the amount of the nitrogen in the Au films regulated in the process of their magnetron sputtering assisted with nitrogen-containing discharge gas.

Surface Activated Bonding of Glass Using Aluminum Oxide Intermediate Layer for Microchannel Fabrication

With a huge demand from the society on a more precise and rapid biological molecule detection in a reduced amount of biosamples, biomedical engineering technology has been in rapid development, resulting in a wide range of biosensors using microfluidic systems. For microfluidic structure, glass is still the main material owing to its chemical stability, cost efficiency, and optical characteristics. In order to seal the fluidic channel based on glass materials, glass substrates should be bonded to cover the channel grooves. Conventionally, glass materials are bonded by anodic bonding or hydrophilic bonding at high temperature process, in which the bonding surfaces are bonded via covalent bonds. However, these bondings of glass at high temperature lead to residual stress at the bonding interface and damage to the device on the substrate, especially the biomolecule sensors using enzymes. In addition to the process temperature, the bonding interface should be transparent as a wide range of biosensors utilizes optical measurements to detect biomarkers.For this reason, a room temperature bonding of glass is desirable for the microchannel sealing. As a room temperature direct bonding method of glass, modified surface activated bonding (mSAB) using Si intermediate layer has been reported to achieve a strong bond of glass via Si layers and Fe nano adhesion layers [1]. Although this approach enables the glass bonding at room temperature, the bonding interface is covered with the deposited Si layers, resulting in deteriorated optical characteristics at the bonding interface. Therefore, mSAB using Si intermediate layer is not suitable for the optical measurement of biomolecules in the microchannels.Recently, we reported a new SAB using aluminum oxide (AlO) intermediate layer instead of Si [2]. AlO has excellent optical characteristics such as low absorbance and refraction index uniformity. From the aspect of bonding, thin AlO membrane by ALD has been reported as intermediate layer for hydrophilic bonding [3]. Furthermore, it has been also reported that bulk sapphire is bonded by standard SAB process, where the sapphire surfaces are activated by Ar ion beam irradiation and bonded through amorphous-like AlO structure [4].In this study, we apply mSAB using AlO intermediate layer for glass substrate and Si substrate with microchannel patterning. The bonding is evaluated from the perspective of the channel sealing.In order to evaluate the sealing by the proposed bonding method, microfluidic channels were realized on a 4 inch and 525 µm thick Si wafer. The patterning consists of 64x64 inlet ports 100 µm diameter, 46-142 µm wide microchannels, 4x4 mm2 cavity, and capillary pump. For the fabrication of the microfluidic components, inductively coupled plasma reactive ion etching (ICP-RIE) was employed. For the sealing of the microchannels on the Si wafer, mSAB using AlO intermediate layer was conducted. The substrates are activated by Ar ion beam and the AlO layers are deposited by ion beam sputtering, followed by contact and press. After sealing by the wafer bonding, through-glass holes were fabricated by sand blast etching to enable flow in the channels.In order to evaluate the sealing of the microfluidic system by the proposed bonding method, first, scanning acoustic tomography (SAT) was conducted. As shown in Figure, the whole structure is sealed without significant voids.Additionally, we also evaluated the sealing of the microfluidic structure by a flow test. A droplet of phosphate buffered-saline (PBS) as a model liquid of biosample was put on the inlet ports. As a result, PBS flow was observed through the microchannels and capillary pump without leakage. Therefore, it can be said that the proposed bonding method successfully sealed the microfluidic system and the bonding interface kept its transparency.From these result, it is indicated that the developed bonding method is suitable for the microchannel device fabrication by realizing a transparent bonding interface at room temperature. MMR Howlader, S. Suehara, and T. Suga. Sensors and Actuators A: Physical, 127(1):31–36, 2006.Takeuchi, F. Mu, Y. Matsumoto and T. Suga, 6th International Workshop on Low Temperature Bonding for 3D Integration (LTB-3D), Kanazawa, Japan, 2019, pp. 85-85.Ikku, M. Yokoyama, R. Iida, M. Sugiyama, Y. Nakano, M. Takenaka, and S. Takagi, 23rd International Conference on Indium Phosphide and Related Materials, May 2011, pp. 1–4.Takagi, Y. Kurashima, A. Takamizawa, T. Ikegami, and S. Yanagimachi, Jpn. J. Appl. Phys., Vol. 57, 02BA04, 2017. Figure 1