Ar Ion Irradiation Research Articles

Investigations of Ar ion irradiation effects on nanocrystalline SiC thin films

The effects of 800keV Ar ion irradiation on thin nanocrystalline SiC films grown on (100) Si substrates using the pulsed laser deposition (PLD) technique were investigated. On such PLD grown films, which were very dense, flat and smooth, X-ray reflectivity, glancing incidence X-ray diffraction and nanoindentation investigations were easily performed to evaluate changes induced by irradiation on the density, surface roughness, crystalline structure, and mechanical properties. Results indicated that the SiC films retained their crystalline nature, the cubic phase partially transforming into the hexagonal phase, which had a slightly higher lattice parameter then the as-deposited films. Simulations of X-ray reflectivity curves indicated a 3% decrease of the films density after irradiation. Nanoindentation results showed a significant decrease of the hardness and Young's modulus values with respect to those measured on as-deposited films. Raman and X-ray photoelectron spectroscopy investigations found an increase of the CC bonds and a corresponding decrease of the SiC bonds in the irradiated area, which could explain the degradation of mechanical properties.

Carbon : nickel nanocomposite templates - predefined stable catalysts for diameter-controlled growth of single-walled carbon nanotubes.

Carbon : nickel (C : Ni) nanocomposite templates (NCTs) were used as catalyst precursors for diameter-controlled growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD). Two NCT types of 2 nm thickness were prepared by ion beam co-sputtering without (type I) or with assisting Ar(+) ion irradiation (type II). NCT type I comprised Ni-rich nanoparticles (NPs) with defined diameter in an amorphous carbon matrix, while NCT type II was a homogenous C : Ni film. Based on the Raman spectra of more than 600 individual SWCNTs, the diameter distribution obtained from both types of NCT was determined. SWCNTs with a selective, monomodal diameter distribution are obtained from NCT type I. About 50% of the SWCNTs have a diameter of (1.36 ± 0.10) nm. In contrast to NCT type I, SWCNTs with a non-selective, relatively homogeneous diameter distribution from 0.80 to 1.40 nm covering 88% of all SWCNTs are obtained from NCT type II. From both catalyst templates predominantly separated as-grown SWCNTs are obtained. They are free of solvents or surfactants, exhibit a low degree of bundling and contain negligible amounts of MWCNTs. The study demonstrates the advantage of predefined catalysts for diameter-controlled SWCNT synthesis in comparison to in situ formed catalysts.

Structural and mechanical properties changes induced in nanocrystalline ZrC thin films by Ar ion irradiation

Thin ZrC films (<500 nm), grown on (100) Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser, were irradiated by 800 keV Ar ion at room temperature under a fixed flux of 1011 cm2 s−1 with fluences ranging from 1 × 1014 at/cm2 to 2 × 1015 at/cm2. Glancing incidence X-ray diffraction, X-ray reflectivity, transmission electron microscopy and nanoindentation investigations were used to study the structural modifications in the films' density, composition and mechanical properties induced by irradiation. After irradiation, the lattice parameter and crystallite size slightly increased, while the films' density decreased. Significant decreases in nanohardness and Young modulus values were also measured after irradiation at 1 × 1014 at/cm2 and 1 × 1015 at/cm2 fluences. No further major decreases were observed for a fluence of 2 × 1015 at/cm2. Scanning transmission electron microscopy and energy dispersive X-ray analysis showed a decrease in the Zr/C values in the irradiated film from surface towards the Si substrate.

Improved cellular response of ion modified poly(lactic acid-co-glycolic acid) substrates for mouse fibroblast cells

In this report, the effects of argon (Ar) ion irradiation on poly(lactic acid-co-glycolic acid) (PLGA) substrates on biocompatibility were studied. PLGA scaffold substrates were prepared by spin coating glass surfaces with PLGA dissolved in anhydrous chloroform. Previously, we showed that surface modifications of PLGA films using ion irradiation modulate the inherent hydrophobicity of PLGA surface. Here we show that with increasing ion dose (1×1012 to 1×1014ions/cm2), hydrophobicity and surface roughness decreased. Biocompatibility for NIH3T3 mouse fibroblast cells was increased by argon irradiation of PLGA substrates. On unirradiated PLGA films, fibroblasts had a longer doubling time and cell densities were 52% lower than controls after 48h in vitro. Argon irradiated PLGA substrates supported growth rates similar to control. Despite differences in cell cycle kinetics, there was no detectible cytotoxicity observed on any substrate. This demonstrates that argon ion irradiation can be used to tune the surface microstructure and generate substrates that are more compatible for the cell growth and proliferation.

UV-Vis studies of 800 keV Ar ion irradiated NiO thin films

Abstract We report the evolution of optical absorption properties of 800 keV Ar ion irradiated NiO thin films through UV-Vis characterization. Our results indicate the existence of both Mott-Hubbard (d → d transition) and charge-transfer (p → d transition) characteristic of NiO. The optical band gap of NiO increases from 3.58 to 3.75 eV when irradiated at the fluence of 5 × 1014 ions cm-2 but it does not show any remarkable variation upon 800 keV Ar ion irradiation at higher fluences. The refractive index and electron polarizability at different ion fluences have been determined from the optical band gap. Both refractive index and electron polarizability follow an opposite trend to that of the energy gap as a function of ion fluence.

Native Defects And Optical Properties Of Ar Ion Irradiated ZnO

MeV Argon (Ar) ion irradiation turns white coloured ZnO to yellowish (fluence 1 × 10 14 ions/cm 2 ) and then reddish brown (1 × 10 16 ions/cm 2 ). At the same time the material becomes much more conducting and purely blue luminescent for the highest fluence of irradiation. To get insight on the defects in the irradiated samples Ultraviolet-visible (UV-vis) absorption, Raman, and photoluminescence (PL) spectroscopy and Glancing Angle X-Ray Diffraction (GAXRD) measurements have been carried out. Enhancement of overall disorder in the irradiated samples is reflected from the GAXRD peak broadening. UV-vis absorption spectra of the samples shows new absorption bands due to irradiation. Complete absorption in the blue region of the spectrum and partial absorption in the green and red region changes the sample colour from white to reddish brown. The Raman peak representing wurtzite structure of the ZnO material (~ 437 cm -1 ) has decreased monotonically with the increase of irradiation fluence. At the same time, evolution of the 575 cm -1 Raman mode in the irradiated samples shows the increase of oxygen deficient disorder like zinc interstitials (IZn) and/or oxygen vacancies (VO) in ZnO. PL spectrum of the yellow coloured sample shows large reduction of overall luminescence compared to the unirradiated one. Further increase of fluence causes an increase of luminescence in the blue region of the spectrum. The blue-violet emission can be associated with the interstitial Zn (IZn) related optical transition. The results altogether indicates IZn type defects in the highest fluence irradiated sample. Large changes in the electrical resistance and luminescent features of ZnO using Ar ion beam provides a purposeful way to tune the optoelectronic properties of ZnO based devices. Copyright © 2015 VBRI press.

Structural manipulation in Ge by swift heavy ions governed by electron–phonon coupling strength

The effect of electron–phonon coupling strength in structural manipulation of different degrees of pre-damaged Ge by swift heavy ions (SHI) has been investigated. Starting with c-Ge (100), three sets of samples were prepared with various degrees of damage, i.e. isolated amorphous pockets, connected amorphous zones and continuous amorphous layer by 100 keV Ar ion irradiation. Structural changes in these samples induced by 100 MeV Ag ions were investigated by RBS/C, micro-Raman spectroscopy and XTEM studies. Results show that the sample having isolated amorphous pockets undergoes re-crystallization whereas the sample having uniform amorphous layer shows volume expansion with formation of nanorod-like structures, after SHI irradiation. In this work, it is emphasized that the different degrees of pre-damage have a prominent role against SHI-induced structural manipulation under different laws or equations.

Comprehensive identification of mutations induced by heavy-ion beam irradiation in Arabidopsis thaliana.

Heavy-ion beams are widely used for mutation breeding and molecular biology. Although the mutagenic effects of heavy-ion beam irradiation have been characterized by sequence analysis of some restricted chromosomal regions or loci, there have been no evaluations at the whole-genome level or of the detailed genomic rearrangements in the mutant genomes. In this study, using array comparative genomic hybridization (array-CGH) and resequencing, we comprehensively characterized the mutations in Arabidopsis thaliana genomes irradiated with Ar or Fe ions. We subsequently used this information to investigate the mutagenic effects of the heavy-ion beams. Array-CGH demonstrated that the average number of deleted areas per genome were 1.9 and 3.7 following Ar-ion and Fe-ion irradiation, respectively, with deletion sizes ranging from 149 to 602,180 bp; 81% of the deletions were accompanied by genomic rearrangements. To provide a further detailed analysis, the genomes of the mutants induced by Ar-ion beam irradiation were resequenced, and total mutations, including base substitutions, duplications, in/dels, inversions, and translocations, were detected using three algorithms. All three resequenced mutants had genomic rearrangements. Of the 22 DNA fragments that contributed to the rearrangements, 19 fragments were responsible for the intrachromosomal rearrangements, and multiple rearrangements were formed in the localized regions of the chromosomes. The interchromosomal rearrangements were detected in the multiply rearranged regions. These results indicate that the heavy-ion beams led to clustered DNA damage in the chromosome, and that they have great potential to induce complicated intrachromosomal rearrangements. Heavy-ion beams will prove useful as unique mutagens for plant breeding and the establishment of mutant lines.

Effect of Ar-ion Irradiation on the Field-emission Properties of Screen-printed Carbon-nanotube Field Emitters

Effect of Ar-ion Irradiation on the Field-emission Properties of Screen-printed Carbon-nanotube Field Emitters

Oxidation behavior of an 11Cr ferritic–martensitic steel after Ar-ions irradiation in supercritical water

Corrosion behavior of an 11Cr ferritic–martensitic steel before and after surface modification by Ar-ions irradiation in supercritical water (SCW) at 823K (550°C)/25MPa with different exposure times was investigated to understand the influence of irradiation on corrosion resistance of the steel in SCW. The spallation of oxide layer occurred in the region with Ar-ions irradiation after exposed for 100h. Corrosion morphology revealed a porous structure in the region without irradiation. Filamentous MnCr2O4 oxides were observed in the oxide layer spalling region with a low radiation intensity corresponding to a dose of about 5.65dpa. Many nano-sized oxides were observed in the oxide layer spalling region with a high radiation intensity corresponding to a dose of 10dpa. Oxide size was gradually increased over exposure times but grow rate increased slowly. The diameter of nano-sized oxides was only 200–300nm after exposed for 1000h.

Anisotropic surroundings effects on photo absorption of partially embedded Au nanospheroids in silica glass substrate

The influence of a directly adjacent or an anisotropic surrounding medium alters the plasmonic properties of a nanoparticle because it provides a mechanism for symmetry breaking of the scattering. Given the success of ion irradiation induced embedment of rigid metallic nanospheroids into amorphous substrate, it is possible to examine the effect of the silica glass substrate on the plasmonic properties of these embedded nanospheroids. In this work presented here, discrete dipole approximation (DDA) calculations for the Au nanospheroids’ optical properties were performed based on 3–dimensional (3D) configuration extracted from planar SEM micrographs and cross–sectional TEM micrographs of the Au nanospheroids partially embedded in the silica glass, and the well–matched simulations with respect to the experimental measurements could demonstrate the dielectric constant at the near surface of silica glass decreased after Ar–ion irradiation.

Influence of Ar-ions irradiation on the oxidation behavior of ferritic–martensitic steel P92 in supercritical water

The corrosion behavior of ferritic–marensitic steel P92 with and without Ar-ions irradiation in supercritical water at 823K(550°C)/25MPa for different exposure times was investigated by a variety of characterization techniques. A distinct difference in oxidation morphology between irradiated and unirradiated samples was observed. The oxide morphology of samples with a relatively moderate radiation intensity was similar with that of samples without irradiation. Many small oxide particles were observed in the region with a relatively high radiation intensity but their size was increased gradually with increasing exposure times. Exfoliation of oxide layer occurred for irradiated samples exposed for 100h. Chromium-rich oxide layer with a chromium content of more than 20wt pct along with a small-scale three-layer oxide structures were observed in Ar-ions irradiated samples, arising from the microstructural change in steel samples after the irradiation. Mechanism for the exfoliation of oxide layer is also discussed.

Argon Ion Irradiation Effect on the Magnetic Properties of Fe-Al2O3 Nano Granular Film

We studied the effect of Argon (Ar) ion irradiation on Fe-Al2O3 nanogranular thin film. X-ray diffraction (XRD) patterns show that the ion dose might promote the growth of the Fe2O3 phase from an amorphous phase to a crystalline phase. The magnetic and magnetoresistance properties were investigated using a vibrating sample magnetometer (VSM) and a four point probe (FPP). The results suggest that percolation concentration occurred at the 0.55 Fe volume fraction and with a maximum magnetoresistance (MR) ratio of 3%. The present MR ratio was lower than that of previous results, which might be related to the existence of the α-Fe2O3 phase promoted by Ar ion irradiation. CEMS spectra show ion irradiation induces changes from superparamagnetic characteristics to ferromagnetic ones, which indicates the spherical growth of Fe particles in the Al2O3 matrix.

Ar ions irradiation effects in ZrN thin films grown by pulsed laser deposition

Thin ZrN films (<500nm) were grown on (100)Si substrates at a substrate temperature of 500°C by the pulsed laser deposition (PLD) technique using a KrF excimer laser under CH4 or N2 atmosphere. Glancing incidence X-ray diffraction showed that films were nanocrystalline, while X-ray reflectivity studies indicated that the films were very dense and with a smooth surface. The films were used to study the effect of 800keV Ar ion irradiation on their structure and properties. After irradiation with a dose of 1014at/cm2 the lattice parameter and crystallites size did marginally change. However, after irradiation with a 1015at/cm2 dose, a clear increase in the lattice parameter accompanied by a significant decrease in nanohardness and Young modulus were observed.

The effects of swift heavy-ion irradiation on helium-ion-implanted silicon

Cross-sectional transmission electron microscopy (XTEM) was used to study the effects of irradiation with swift heavy ions on helium-implanted silicon. 〈100〉-oriented silicon wafers were implanted with 30keV helium to a dose of 3×1016He+/cm2 at 600K. Subsequently, the helium-implanted Si wafers were irradiated with 792MeV argon ions. The He bubbles and extended defects in the wafers were examined via XTEM analysis. The results reveal that the mean diameter of the He bubbles increases upon Ar-ion irradiation, while the number density of the He bubbles decreases. The microstructure of the He bubbles observed after Ar-ion irradiation is comparable to that observed after annealing at 1073K for 30min. Similarly, the mean size of the extended defects, i.e., Frank loops, increases after Ar-ion irradiation. Possible mechanisms are discussed.

Ion irradiation for improved graphene network formation in carbon nanotube growth

Ion irradiation of carbon nanotubes very often leads to defect formation. However, we have recently shown that Ar ion irradiation in a limited energy window of 10–25eV may enhance the initial cap nucleation process, when the carbon network is in contact with the metal nanocatalyst. Here, we employ reactive molecular dynamics simulations to demonstrate that ion irradiation in a higher energy window of 10–35eV may also heal network defects after the nucleation stage through a non-metal-mediated mechanism, when the carbon network is no longer in contact with the metal nanocatalyst. The results demonstrate the possibility of beneficially utilizing ions in e.g. plasma-enhanced chemical vapour deposition of carbon nanotubes.

Influence of the irradiation temperature on the surface structure and physical/chemical properties of Ar ion-irradiated bulk metallic glasses

Surface treatments using multiple Ar ion irradiation processes with a maximum energy and fluence of 200keV and 1×1016ions/cm2, respectively, have been performed on two different metallic glasses: Zr55Cu28Al10Ni7 and Ti40Zr10Cu38Pd12. Analogous irradiation procedures have been carried out at room temperature (RT) and at T=620K (≈0.9Tg, where Tg denotes the glass transition). The structure, mechanical behavior, wettability and corrosion resistance of the irradiated alloys have been compared with the properties of the as-cast and annealed (T=620K) non-irradiated specimens. While ion irradiation at RT does not significantly alter the amorphous structure of the alloys, ion irradiation close to Tg promotes decomposition/nanocrystallization. Consequently, the hardness (H) and reduced Young’s modulus (Er) decrease after irradiation at RT but they both increase after irradiation at 620K. While annealing close to Tg increases the hydrophobicity of the samples, irradiation induces virtually no changes in the contact angle when comparing with the as-cast state. Concerning the corrosion resistance, although not much effect is found after irradiation at RT, an improvement is observed after irradiation at 620K, particularly for the Ti-based alloy. These results are of practical interest in order to engineer appropriate surface treatments based on ion irradiation, aimed at specific functional applications of bulk metallic glasses.

Temporal evolution and nature of nanostructures on Au(111)

We have studied the nature of nanostructures and their time evolution on Au(111) created by argon ion irradiation followed by either subsequent or simultaneous annealing at different temperatures. For subsequently annealed surface, an initial linear decrease in the areas of the islands and pits is obtained with time. We show that the mass flow of the surface atoms is governed by the rate of detachment, rather than the rate of diffusion. The small islands and pits are found to disappear. In contrast, the areas of the large islands and pits initially decrease and become nearly constant as they attain a regular hexagonal shape. On the other hand, the simultaneously irradiated and annealed Au surface is much smoother with wide terraces and mostly pits of irregular hexagonal shape are observed. We also show that local stepped areas that resemble vicinal surfaces can form on Au(111) due to Ar ion irradiation.

Designing self-organized nanopatterns on Si by ion irradiation and metal co-deposition

Dot and ripple nanopatterns on Si surfaces with defined symmetry and characteristic dot spacings of 50–70 nm were created by 1 keV Ar ion irradiation at normal incidence and simultaneous co-deposition of Fe atoms at grazing incidence. Fe was continuously supplied from different sputter targets surrounding the Si substrate, leading to a steady-state Fe content in the near-surface region of the substrates. The pattern formation is self-organized, most probably caused by ion-induced phase separation. Patterns were analyzed with atomic force microscopy and the Fe content in the irradiated layer was measured with Rutherford backscattering. The symmetries of the produced patterns are isotropic, four-fold symmetric, three-fold symmetric and various types of two-fold symmetric patterns, depending on the geometrical arrangement of the sputter targets. Pattern formation was studied for a steady-state coverage of Fe between 0.5 and 3.3 × 1015 Fe cm−2. The threshold coverage for the onset of pattern formation is about 0.5–1 × 1015 Fe cm−2. The coherence length of the patterns is comparable to the average dot spacing. Nevertheless, the autocorrelation analysis reveals a residual long-range periodicity of some patterns. The dot spacing can be adjusted between about 20 nm and several hundred nm depending on the ion species and ion energy.

Transformation of multiwalled carbon nanotubes to amorphous carbon nanorods under ion irradiation

Amorphous carbon nanorods were synthesized from hollow multiwalled carbon nanotubes (MWCNTs) by low-energy Ar ion irradiation at room temperature. The obtained nanorods were investigated by Raman spectroscopy, transmission electron microscopy (TEM), soft X-ray photoelectron spectroscopy (XPS), and soft X-ray absorption spectroscopy (XAS). It was found that the diameter of the MWCNTs significantly increased with increasing the fluence. Finally, the original hollow structure and the graphite (002) TEM diffraction spots of MWCNTs completely disappeared and a broadening of Raman spectra occurred, indicating the amorphization of MWCNTs. The increase in the diameter by the irradiation can be explained by the bending and the randomization of the broken carbon hexagonal networks, and the accumulation of knocked-on atoms. The XPS and XAS measurements also support the formation of amorphous carbon nanorods.