Ion Beam Irradiation Research Articles

Study of inter-diffusion of gold in copper in the presence of single layer graphene

• Graphene acts as a diffusion barrier for interdiffusion of Au in Cu upto 220°C. • From 240°C to 280°C, grain boundary diffusion is dominant in Au/Gr/Cu. • Slower ion beam mixing is observed in Au/Gr/Cu compared to Au/Cu sample. • Disorder is more in graphene upon annealing and amorphization upon irradiation. Rutherford backscattering spectrometry (RBS) has been used to examine the inter-diffusion behaviour in Au thin films (∼30 nm) deposited on CVD grown monolayer Graphene on copper (Au/Gr/Cu) with reference to gold film deposited on copper (Au/Cu), under thermal annealing and ion beam irradiation processes. Graphene is acting as a diffusion barrier in Au/Gr/Cu upto 220 °C for the inter-diffusion of Au in Cu in thermal annealing process, while interdiffusion occurs below 200 °C in Au/Cu. In high temperature regime, bulk diffusion mechanism is dominant in Au/Cu system whereas grain boundary diffusion is dominant in Au/Gr/Cu system. The dominant grain boundary diffusion in Au/Gr/Cu indicates that grain boundary defects in graphene play a major role in inter-diffusion process. Upon 9 MeV Si 6+ ion irradiation, there is no ion beam mixing upto 5 × 10 15 ions/cm 2 and at the ion fluence of 3 × 10 16 ions/cm 2 , ion beam mixing is observed in both Au/Cu and Au/Gr/Cu samples, with lower ion beam mixing rate and mixing efficiency for Au/Gr/Cu sample. This implies that graphene interlayer can prevent ion beam mixing to a certain extent due to its impermeable nature. The blue shift of Raman spectroscopy peaks G and 2D and the splitting of G-peak from graphene barrier layer signifies the compressive strain in Au deposited and thermally annealed Gr/Cu samples. Even though interlayer graphene can reduce the interdiffusion in Au/Cu system modestly, it becomes disordered with the formation of sp 3 carbon bonds with increase in annealing temperatures and ion fluences, thereby loosing its impermeable nature.

Formation of core-shell nanostructure through wrapping of cuprous oxide nanowires by hydrogen titanate nanotubes

Recent developments of heterojunction-based devices through bottom-up approach such as sensors, light-emitters, energy generation and storage have emerged with great interest due to their wide range of operation and application related flexibilities. This work demonstrates how as-grown hydrogen titanate nanotubes (HTNT) bend and wrap on pristine curpous oxide nanowires (CONW) when mixed together. The unique architecture of wrapping followed by junction formation enhances the active surface area and reduces the contact resistance between the adjacent CONW and HTNT. Such a film upon further ion beam irradiation produces a large-scale network of hetero- and homo-junctions. This newly formed thin film surface upon irradiation shows strong water repelling properties and higher electrical conductivity. The wrapping mechanism, bond formation and the change of conductivity are explained using first principles calculations. The ion beam modifications and large-scale joining are predicted by state-of-the-art TRI3DYN simulation, which is based on binary collision approximation and simulated in a Monte Carlo approach. The observed wrapping and heterojunction are expected to provide excellent mechanical strength and flexibility, which are suitable for fabrication of flexible electronic devices.

Influence of proton irradiation on phase variation and optical properties of VO2(B) thin film

ABSTRACT The present work is focused on the fabrication of VO2(B) thin films by magnetron sputtering followed by proton irradiation using 5 MeV tandem accelerator. For the study of phase transitions, the proton ion beam applied was to the VO2(B) thin films at the rate of 1 × 1015 ions/cm2, 2 × 1015 ions/cm2, 7.5 × 1015 ions/cm2, 5 × 1016 ions/cm2 respectively. The VO2(B) thin-film shows prominent phase variation from VO2(B) to VO2(A) along with the amorphization phenomenon with the increasing doses of proton ions. The diffused reflectance spectroscopy shows increasing trends in reflectance from 20 to 39%. Energy bandgap was determined using a Tauc plot showing efficient decreasing trends w.r.t ion beam doses. Raman spectroscopy shows vibrations in the range from 144 to 883 cm−1 with different bands, confirming the phase transition towards VO2(A) by proton ion beam irradiation. The results are useful and promising for the smart use of various phases of VO2(B) thin film.

Surface preparation of metal films by gas cluster ion beams using organic acid vapor for Cu–Cu bonding

Surface-activated bonding (SAB) of Cu by gas cluster ion beam (GCIB) irradiation with acetic acid vapor was studied. GCIB irradiation realizes surface smoothing and surface reaction enhancement without severe damage. Therefore, it is promising for SAB. In this study, acetic acid vapor was introduced during Ar-GCIB irradiation to assist the removal of surface oxides on the Cu surface. XPS results showed that Cu(OH)2 was effectively removed by reaction with adsorbed acetic acid, and there was no residue by acetic acid adsorption. In addition, surface roughness decreased by Ar-GCIB irradiation with acetic acid because of the preferential removal of protrusion. Preliminary bonding experiments showed an increase of Cu–Cu bond strength by Ar-GCIB irradiation with acetic acid vapor.

One-step method to enhance biotribological properties and biocompatibility of DLC coating by ion beam irradiation

A one-step method was developed to create a highly biocompatible micropatterned surface on a diamond-like carbon (DLC) through irradiation with a nitrogen ion beam and thus enhance the biocompatibility of osseointegrated surfaces and biotribological performance of articular surfaces. The biocompatibility and biotribological mechanisms were analyzed in terms of the structure and morphology of DLC. It was demonstrated that a layer enriched in sp3 C−N bonds was formed on the surface of the DLC after nitrogen ion beam irradiation. Moreover, with an increase in the radiation dose, the content of sp3 C−N on the DLC surface increased significantly, and the biocompatibility was positively correlated with it. The adhesion of the MC3T3 osteoblasts increased significantly from 32% to 86% under an irradiation dose of 8 × 1015 ions/cm2. In contrast, the micropattern had a significant negative effect on the adhesion of the osteoblasts as it physically hindered cell expansion and extension. The micropattern with a depth of 37 nm exhibited good friction properties, and the coefficient of friction was reduced by 21% at relatively high speeds.

Investigation of radiation damage using thermal spike model for SHI irradiation on Al2O3

The material exposed to energetic radiation may change its properties and performance. Ion beam irradiation is an established method to investigate radiation damage in materials. In the present study, SRIM code is employed as a tool to determine the electronic and nuclear energy losses and displacement per atom (DPA) associated with the damage induced in Al2O3 using 100 MeV Au ion. We have further studied the creation of 100 MeV Au ion induced molten zone along the ion track in Al2O3 in the framework of the thermal spike (TS) model. Using the in-elastic thermal spike model, elastic thermal spike model, and unified thermal spike model, the evolution of lattice temperature and latent track radius as a function of depth of Al2O3 for 100 MeV Au ion irradiation are investigated. The current results demonstrate that the latent track radius shows a U-shaped variation based on the combined effect of electronic stopping power and nuclear stopping power. In order to corroborate these results, an additional irradiation experiment was performed using swift heavy ion (SHI), 100 MeV Au ions with fluence 1×1014 ions/cm2 for Al2O3. To investigate the structural properties, surface morphology and to identify the defects in the samples, pristine and irradiated Al2O3 samples were characterized by Grazing Incident X-Ray Diffraction (GIXRD), Atomic Force Microscopy (AFM) and Photoluminescence Spectroscopy (PL). AFM study shows the increase in roughness after SHI irradiation. A decrease in intensity of PL spectra upon SHI irradiation indicates the formation of new defects and disordered structures in the material, which is quite in agreement with the theoretical results.

Human Neocortex Layer Features Evaluated by PIXE, STIM, and STXM Techniques.

The human neocortex has a cytoarchitecture composed of six layers with an intrinsic organization that relates to afferent and efferent pathways for a high functional specialization. Various histological, neurochemical, and connectional techniques have been used to study these cortical layers. Here, we explore the additional possibilities of swift ion beam and synchrotron radiation techniques to distinguish cellular layers based on the elemental distributions and areal density pattern in the human neocortex. Temporal cortex samples were obtained from two neurologically normal adult men (postmortem interval: 6-12h). A cortical area of 500 × 500 μm2 was scanned by a 3MeV proton beam for elemental composition and areal density measurements using particle induced x-ray emission (PIXE) and scanning transmission ion microscopy (STIM), respectively. Zinc showed higher values in cortical layers II and V, which needs a critical discussion. Furthermore, the areal density decreased in regions with a higher density of pyramidal neurons in layers III and V. Scanning transmission X-ray microscopy (STXM) revealed the cellular density with higher lateral resolution than STIM, but not enough to distinguish each cortical lamination border. Our data describe the practical results of these approaches employing both X-ray and ion-beam based techniques for the human cerebral cortex and its heterogeneous layers. These results add to the potential approaches and knowledge of the human neocortical gray matter in normal tissue to develop improvements and address further studies on pathological conditions.

Superior Performance in Liquid Crystal Alignment of Polystyrene-Block-Poly(ethylene-ran-butylene)-Block-Polystyrene-Graft-Maleic Anhydride Film Irradiated with Ion Beam

We studied the change of the surface and liquid crystal (LC) alignment characteristics of Polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleic anhydride (SEBS-g-MA) film according to ion beam (IB) irradiation. Atomic force microscopy (AFM) analysis revealed that IB irradiation reduces peaks and creates a wrinkled structure. X-ray photoelectron spectroscopy (XPS) analysis revealed that IB irradiation disintegrates the C–C bonds and makes C–O bonds, creating a dipole-dipole interaction, which improves the LC alignment characteristics. Through polarized optical microscopy (POM) analysis, it was found that the best LC alignment characteristics can be obtained after 120 s of IB irradiation. It was found that the anisotropy caused by the ion beam contributed more to the liquid crystal alignment in homogeneous direction than the one caused by the wrinkle structure.

Changing the structural and electronic properties of graphene and related two-dimensional materials using ion beam irradiation with NaCl sacrificial layers

Changing the structural and electronic properties of graphene and related two-dimensional materials using ion beam irradiation with NaCl sacrificial layers

In Situ Fabrication, Manipulation, and Mechanical Characterization of Free‐Standing Silica Thin Films Using Focused Ion Beam Scanning Electron Microscopy

AbstractDetermination of mechanical properties of (silica) thin films is important for the development of new applications. However, a versatile approach for small‐scale sample fabrication and in situ mechanical testing of these materials is currently lacking which can overcome the existing difficulties in conventional testing approaches. Here, it is shown that by combining focused ion beam scanning electron microscopy (FIB‐SEM) with micromanipulators free‐standing silica beams of the desired dimensions can be fabricated. Using in situ bending tests on such beams inside the SEM and finite element method simulations, the Young's modulus of thin‐film silica and the effects of gallium ion beam radiation on Young's modulus are determined. Furthermore, the effects of controlled relative humidity on the mechanical behavior of silica beams are investigated. The demonstrated FIB‐SEM approach can be extended to other materials and preparation conditions to measure, model, and optimize mechanical properties of thin films for a wide range of (coating) applications.

Modification of magnetic properties in Tb–Fe/Gd–Fe/Tb–Fe trilayer using ion-beam irradiation

Modification of magnetic properties in Tb–Fe/Gd–Fe/Tb–Fe trilayer using ion-beam irradiation

Liquid crystals alignment and switching between surface reinforced poly(ethylene-co-vinyl acetate) thin layers

The alignment characteristics of liquid crystals (LCs) on poly(ethylene-co-vinyl acetate) (PEVA) films via ion-beam (IB) irradiation at incidence angles of 15°, 45°, or 75° were investigated. Uniform and homogeneous LC alignment were achieved with a PEVA film IB-irradiated at an incidence angle of 45°. Physicochemical modification progressed by IB irradiation were examined by using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The AFM results show that the plasma argon ions penetrated and thereby increased the surface roughness and decreased kurtosis of the PEVA. The XPS results suggest that chemical reconstruction of the PEVA film induced the van der Waals forces and dipole-dipole interactions with the LCs. These transformations resulted in uniform LC alignment at 45° IB incident angle, as confirmed by polarized optical microscopy and pre-tilt angle measurements. The 45° incidence-angle IB-irradiated PEVA film also showed high transmittance in the visible light region. A twisted nematic LC cell based-on the PEVA film showed successful electro-optical performance as stable switching behavior and fine operation characteristics. These results indicate that IB irradiation is an effective method for uniform LC alignment and the 45° incidence-angle IB-irradiated PEVA film can be adopted for LC alignment in future LC display applications.

Local control of magnetic interface effects in chiral Ir|Co|Pt multilayers using Ga+ ion irradiation

Skyrmions are topologically protected chiral spin textures that have shown promise as data carriers in future spintronic applications. They can be stabilized by the interfacial Dzyaloshinskii-Moriya interaction (iDMI) in material systems with inversion asymmetry and spin-orbit coupling, such as Ir$|$Co$|$Pt multilayers. The ability to locally tune such interface interactions, and hence the skyrmion energy, could greatly enhance the nucleation and control of skyrmions in racetrack type devices. In this work, we investigate local tuning of the iDMI and perpendicular magnetic anisotropy (PMA) using focussed Ga$^{+}$ ion beam irradiation, in an Ir$|$Co$|$Pt multilayer system. We show that the magnitude of the interface contribution to both effects can be significantly reduced by the irradiation with Ga$^{+}$ ions. This leads to a reduction by a factor two of the domain wall energy density, while still preserving the N\'{e}el character of the domain walls. Hence, we postulate that Ga$^{+}$ ion irradiation is an effective way to locally reduce the energy barrier for skyrmion nucleation, providing a novel pathway for targeted skyrmion nucleation in racetrack type devices.

Nanopatterning of rotating highly oriented pyrolytic graphite (0001) surfaces by ion beam irradiation: Experiments and modeling

We produce ordered surface nanostructures on azimuthally rotating HOPG(0001) by irradiation with low-energy ion beams. Thus, small dots at low fluences evolve into cellular structures at large fluences. This transition is a consequence of the fast growth of dots and their subsequent concatenation to form walls along the grain boundaries, leading to cells. The walls compete and ripen with continued ion beam irradiation, resulting in both coarsening and roughening of the cell pattern. We reproduce the same morphological and scaling behavior using different ions, Kr or Ar, so the mechanisms involved in pattern formation and coarsening are robust. We compare the experimental findings with simulations of a nonlinear continuum model based on ion-driven viscous flow, which reproduces many qualitative properties seen in the experiments. Such a comparison underscores the need for a suitable consideration of both external noise and the grain structure of the target to fully account for the large-scale properties of the process.

Effect of Annealing and Ion Beam Irradiation on AC Electrical Properties for Gold Sputtered PM-355

Deposition of different gold thickness on PM-355 cleaned by ethanol forming thin films using magnetron sputtering. Gold layer with thickness 300, 400, 500, 700, 1000, 1300, and 1500 nm were deposited to prepare Au / PM-355 thin films. Then, ac electrical properties response of thin films for a wide frequency range 20Hz - 5MHz were measured at roomtemperature. Meanwhile, the measurements of ac conductivity, dielectric constant, and dielectric loss factor were plotted at different frequencies to determine the optimum thickness. Hence, the comparison was done between optimum Au thickness thin films cleaned by two organic solvents and ethanol before annealing at different frequencies. Also, study the effect of annealing and ion beam that extracted radially from conical anode and disc cathode ion source on optimum Au thickness thin film electrical properties. It is found that the annealing increases both dielectric constant, dielectric loss, and ac conductivity of optimum Au thin film at different frequencies. Despite, the nitrogen ion beam effected on these thin films by decreasing the dielectric constant and ac conductivity for all thin films except the chloroform one. Finally, study the comparison between the annealing and followed by ion irradiation thin films. It is noticed the decrease in ac electrical conductivity and dielectric constant at different frequencies.

Carbon Ion Beam Boost Irradiation in Malignant Tumors of the Nasal Vestibule and the Anterior Nasal Cavity as an Organ-Preserving Therapy.

BackgroundSurgery and radiotherapy are current therapeutic options for malignant tumors involving the nasal vestibule. Depending on the location, organ-preserving resection is not always possible, even for small tumors. Definitive radiotherapy is an alternative as an organ-preserving procedure. Carbon ion beam radiotherapy offers highly conformal dose distributions and more complex biological radiation effects eventually resulting in optimized normal tissue sparing and improved outcome. The aim of the current study was to analyze toxicity, local control (LC), and organ preserving survival (OPS) after irradiation of carcinoma of the nasal vestibule with raster-scanned carbon ion radiotherapy boost (CIRT-B) combined with volumetric intensity modulated arc therapy (VMAT) with photons.MethodsBetween 12/2015 and 05/2021, 21 patients with malignant tumors involving the nasal vestibule were irradiated with CIRT-B combined with VMAT and retrospectively analyzed. Diagnosis was based on histologic findings. A total of 17 patients had squamous cell carcinoma (SCC) and 4 had other histologies. In this series, 10%, 67%, and 24% of patients had Wang stages 1, 2, and 3 tumors, respectively. Three patients had pathologic cervical nodes on MRI. The median CIRT-B dose was 24 Gy(RBE), while the median VMAT dose was 50 Gy. All patients with pathologic cervical nodes received simultaneously integrated boost with photons (SIB) up to a median dose of 62.5 Gy to the pathological lymph nodes. Eight patients received cisplatin chemotherapy. All patients received regular follow-up imaging after irradiation. Kaplan–Meier estimation was used for statistical assessment.ResultsThe median follow-up after irradiation was 18.9 months. There were no common toxicity criteria grade 5 or 4 adverse events. A total of 20 patients showed grade 3 adverse events mainly on skin and mucosa. All patients were alive at the end of follow-up. The median OPS after treatment was 56.5 months. The 6- and 24-month OPS were 100% and 83.3%, respectively. All local recurrences occurred within 12 months after radiotherapy. The median progression free survival (PFS) after treatment was 52.4 months. The 6-, 12-, and 24-month PFS rates were 95%, 83.6%, and 74.3%, respectively.ConclusionCIRT-B combined with VMAT in malignant tumors of the nasal vestibule is safe and feasible, results in high local control rates, and thus is a good option as organ-preserving therapy. No radiation-associated grade 4 or 5 acute or late AE was documented.

Surface preparation of metal films by gas cluster ion beams using organic acid vapor for Cu-Cu bonding

Abstract Surface activated bonding of Cu by gas cluster ion beam (GCIB) irradiation with acetic acid vapor was studied. GCIB irradiation realizes surface smoothing and surface reaction enhancement without severe damage. Therefore, it is promising for surface-activated bonding (SAB). In this study, acetic acid vapor was introduced during Ar-GCIB irradiation to assist removal of surface oxides on Cu surface. XPS results showed that Cu(OH)2 was effectively removed by reaction with adsorbed acetic acid, and there was no residue by acetic acid adsorption. In addition, surface roughness decreased by Ar-GCIB irradiation with acetic acid because of the preferential removal of protrusion. Preliminary bonding experiments showed increase of Cu-Cu bond strength by Ar-GCIB irradiation with acetic acid vapor.

Raman and photoluminescence evaluation of ion-induced damage uniformity in ThO2

Nuclear reactor conditions can be emulated in part by exposing potential fuel materials, such as ThO2, to ion beam radiation. Changes in properties can then provide invaluable insight into how the material will perform as a fuel. Here, a hydrothermally grown single crystal of ThO2 is irradiated with 2 MeV H+ and the crystallographic and electronic structure homogeneity and damage extent is investigated. μ-Raman spectroscopy shows that the damage to the crystal face directly exposed to the irradiation is heterogeneous, with the intensity of irradiation-induced peaks altering substantially in relation to the T2g structural peak. Damage on orthogonal faces is more uniform and the damage depth profile is investigated with Raman spectroscopy. The damage as a function of depth is compared to stopping range of ions in matter simulations. Photoluminescence spectroscopy is also employed to investigate the depth profiles and exhibits clear signs of damage, which are discussed.

Electronic structure engineering of 2-D MoS2 sputtered thin films under ion beam irradiation: Induced by controlled defect generation

TMDs (Transition-metal dichalcogenides) come out in contemporary years as a remarkable class of two-dimensional (2D) materials and have allured enormous consideration. In the class of TMD materials, Molybdenum disulfide (MoS 2 ) has unveiled encouraging applications in the domain of photonics, electronics, electrochemistry and energy. Specifically, the defects originated in MoS 2 play a significant role in modifying the magnetic, electronic, catalytic and optical peculiarities of MoS 2 , depicting an applicable way in modifying the efficiency of MoS 2 based devices. The course through which lattice defects influence the MoS 2 peculiarities are unresolved. In the present work, we present comprehensively how lattice defects impact the electronic structure of MoS 2. We have probed the prospect to employ swift heavy ion irradiation for nano-structuring of sputtered 2D MoS 2 thin films. Our extensive study of ion instigated structural, optical and morphological alterations in MoS 2 thin films manifests that resting on the parameters of irradiation profusion of defects can be established. Theoretically, the optical bandgap also has been determined using Density functional theory (DFT). We grow the thin films of MoS 2 by the sputtering method and induced the defect in MoS 2 thin films by ion irradiation. We evaluated how these defects impact the electronic structure of MoS 2 thin films by measurements taken from Raman, X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), UV–visible spectroscopy, Atomic force microscopy (AFM), X-ray diffraction (XRD) and Rutherford backscattering spectroscopy (RBS).

Biosensor for deconvolution of individual cell fate in response to ion beam irradiation

SummaryClonogenic survival assay constitutes the gold standard method for quantifying radiobiological effects. However, it neglects cellular radiation response variability and heterogeneous energy deposition by ion beams on the microscopic scale. We introduce “Cell-Fit-HD4D” a biosensor that enables a deconvolution of individual cell fate in response to the microscopic energy deposition as visualized by optical microscopy. Cell-Fit-HD4D enables single-cell dosimetry in clinically relevant complex radiation fields by correlating microscopic beam parameters with biological endpoints. Decrypting the ion beam’s energy deposition and molecular effects at the single-cell level has the potential to improve our understanding of radiobiological dose concepts as well as radiobiological study approaches in general.