Ar Ion Beam Research Articles

Bandgap tailoring of rutile TiO2(110) via surface patterning with electron cyclotron resonance sputtering

Crystalline TiO2 nanodots have been formed on single crystal rutile TiO2(110) surfaces via ion beam sputtering method by utilizing Ar ion beams from electron cyclotron resonance source. Nearly five times enhancement in absorbance of visible light, ∼5 times increase in luminescence, and ∼0.1 eV narrowing of bandgap are observed for nanodot-patterned surfaces, in the absence of any dopant material. Formation of crystalline rutile TiO2 nanodots and development of Ti interstitials on the TiO2(110) surface, after ion beam sputtering, are responsible for these observations. Results suggest that these nanodot-patterned rutile TiO2 surfaces can become effective photocatalysts.

Nanoadhesion layer for enhanced Si–Si and Si–SiN wafer bonding

Direct wafer bonding of Si–Si and Si–SiN wafers was demonstrated using a nanoadhesion layer at room temperature. The two mating surfaces were cleaned by an Ar-ion beam and simultaneously deposited with ultrathin Fe layers (known as nanoadhesion layers). The ultrathin Fe layers imparted high bond strengths to Si–Si and Si–SiN bonds without heat treatment. Transmission electron microscopy revealed that the Si–Si and Si–SiN interfaces were tightly bonded and defect free. Moreover, the formation of crystalline iron silicide across the interface was found to enhance Si–Si wafer bonding. In addition to FeSi, an amorphous layer formed at the Si–SiN interface, resulting in a high bond strength at room temperature.

Size-control synthesis of structure deficient truncated octahedral Fe3−δO4 nanoparticles: high magnetization magnetites as effective hepatic contrast agents

This study reports the size-controlled synthesis of truncated octahedral Fe3−δO4 nanoparticles varying from 5 to 22 nm in edge length. Size-dependent XRD spectra show that the iron oxide gradually shifted from magnetite toward maghemite as the size decreased. The nonstoichiometric Fe3−δO4 was expressed the resulting iron oxide nanoparticles. The smaller particle size resulted in larger δ value. The size dependence of the XRD, magnetization, and Raman measurements indicate that the 22 nm-sized particles formed magnetite nanoparticles. The saturation magnetization increased linearly as the particle size increased, eventually reaching 94 emu/g, which is comparable to bulk magnetite (92 emu/g). The magnetic behavior of Fe3−δO4 nanoparticles exhibited a transition from superparamagnetism to ferromagnetism when the particles reached 22 nm in size. The XRD, electron diffraction analysis, fast Fourier transform filtering analysis, and Ar ion beam etching results in this study indicate that the presence of metallic iron in the 22 nm-sized magnetite nanoparticles was responsible for their high magnetization. The high magnetization of the 22 nm-sized magnetite was achieved by different surface modification strategies using surfactant (CTAB) and a polymer (PSMA), generating hydrophilic properties. The chosen PSMA-coated magnetites have an r2 relaxivity larger than 200 mM−1 s−1, whereas the commercial Resovist hepatic agent achieves only 91 mM−1 s−1. In an effort to develop highly effective hepatic contrast agents, the PSMA-coated magnetite was injected into BALB/C mice to evaluate the T2* relaxation and image contrast. Results show a greater signal reduction in the liver than Resovist agent. The biodistribution profile of these iron oxide nanoparticles shows significant liver uptake, which is consistent with MRI observations.

Arイオン打ち込み処理による高誘電率ポリイミドフィルム表面のSEM観察

High-resolution scanning electromicroscopy (SEM) is a powerful technique to elucidate surface information. Because Upilex S® film, a polyimide film (PI film), possesses excellent properties such as chemical and heat resistance, it has been used in many flexible printed board fabrications. When surfaces of the PI film with high permittivity are observed using SEM, the thin film coating of a noble metal by evaporation methods is necessary to avoid charging problems. Such a thin film coating creates artifacts on SEM images. Consequently, high-resolution observation often becomes difficult, especially if we attempt to observe the adsorption of nanoparticles such as Pd-Sn catalysts on the PI film. Surface scientists know empirically that Ar ion beam treatment inhibits charging phenomena of the observed samples.To prevent charging problems during SEM observations, we examined Ar ion implantation for the PI film sample with low acceleration voltage (200—300 V) applied to Ar ion gun. Regarding acceleration voltage at 300 V, high-resolution SEM images of the PI film surface were obtained without any thin film coating of noble metal. Furthermore, elemental analyses of the PI film were enabled by energy dispersive X-ray spectrometry (EDS) performed with high current.

Influence of Ag thickness on structural, optical, and electrical properties of ZnS/Ag/ZnS multilayers prepared by ion beam assisted deposition

The structural, optical, and electrical characteristics of zinc sulfide (ZnS)/Ag/ZnS (ZAZ) multilayer films prepared by ion beam assisted deposition on k9 glass have been investigated as a function of Ag layer thickness. The characteristics of ZAZ multilayer are significantly improved up insertion of optimal Ag thickness between ZnS layers. The results show that due to bombardment of Ar ion beam, distinct Ag islands evolve into continuous Ag films at a thin Ag thickness of about 4 nm. The thinner Ag film as a thickness of 2 nm leads to high sheet resistance and low transmittance for the interface scattering induced by the Ag islands or noncontinuous films; and when the Ag thickness is over 4 nm, the ZAZ multilayer exhibits a remarkably reduced sheet resistance between 7–80 Ω/sq for the increase in carrier concentration and mobility of Ag layer, and a high transmittance over 90% for the interference phenomena of multilayers and low absorption and surface scattering of Ag layer. The ZAZ multilayer with 14 nm Ag film has a figure of merit up to 6.32×10−2 Ω−1, an average transmittance over 92% and a sheet resistance of 7.1 Ω/sq. The results suggest that ZAZ film has better optoelectrical properties than conditional indium tin oxide single layer.

Investigation and application of hollow anode glow discharge ion source

In the present work, a new shape of a glow discharge ion source has been designed, fabricated and constructed at Accelerators and Ion Sources Department, Nuclear Research Center, Egyptian Atomic Energy Authority, Egypt. The discharge and output beam characteristics of the ion source at different operating gas pressures have been measured at the optimum distance between the anode and the cathode (3.5 mm) using hydrogen and nitrogen gases. Furthermore, mixture of different gases was studied, e.g., addition of H 2 gas to N 2 gas with different ratios has been investigated. Finally, as an application of this new ion source, ion beam modification of insulators (glass) which depends on glass structure has been achieved. It has been found that, the transmission of light is decreased by coating the glass surface with Ar ion beam more than coating with plasma of Ar gas at the same pressure and the same exposure time. So we could use this ion source as a coating tool for borate glass surface. The parameters affected the glow discharge ion source efficiency have been examined carefully using a mixture of gases. Using helium gas, the glow discharge is in a turbulent state due to instabilities. An investigated H 2–N 2 mixture has been used in order to obtain an optimum percentage of the mixture of the two gases to increase the electric field necessary for ionization balance.

Planar and ridge waveguides formed in LiNbO_3 by proton exchange combined with oxygen ion implantation

We report on the fabrication of planar and ridge waveguides in lithium niobate by proton exchange combined with oxygen ion implantation. The implanted energy ranges from 600 to 1400 keV with a dose of 1 x 10(15) ions/cm(2). The modes in proton exchanged waveguide can be modulated by O ion implantation. There are different damage profiles in proton-exchanged and ion-implanted waveguides in Rutherford backscattering/channeling spectra. The refractive index profile in single-mode waveguide in lithium niobate has been obtained based on Intensity Calculation Method. Also ridge waveguide was fabricated on the basis of planar waveguide by Ar ion beam etching. The measured near-field intensity distributions of the ridge waveguide modes show a reasonable agreement with the simulated ones. The estimated propagation loss was approximately 2.2 dB/cm.

Lithium Niobate Ridge Waveguides Fabricated by Ion Implantation Followed by Ion Beam Etching

A new fabrication method for lithium niobate ridge waveguides is reported. Lithium niobate ridge waveguide with a smooth surface was fabricated by O+ ions implanted combined with Ar ion beam etching. The beam propagation method (BPM) was used to simulate the properties of planar and ridge waveguides by use of a reconstructed refractive index profile. The simulation results match to the experimental results very well, and the loss value of the ridge waveguide is about 2 dB/cm.

Ion Beam Emission in a Low Energy Plasma Focus Device

The characteristics of the Ar ion beam generated in a low energy plasma focus device were investigated. A Mather-type PF device filled with argon gas driven by an 11 μF single capacitor bank was used. A Faraday cup, operating in the bias ion collector mode, is used to estimate the energy spectrum and ion flux along the PF axis. The results of the experiments show the dependence of the energy spectrum on the gas pressure and the anode shape.

Nano-embossed structure on polypropylene induced by low energy Ar ion beam irradiation

The surface morphology evolution of polypropylene (PP) irradiated with an Ar ion beam was explored using a hybrid ion beam system. PP formed the emboss-like nanostructure of ∼ 50 nm induced by the Ar ion beam treatment for shorter ion beam treatment times, while the emboss-like structure was transited into a 3-D long nanofiber-like nanostructure for longer treatment times. The Fourier transform infrared spectra revealed that the polymer chain cross-linking increased with increasing ion treatment time, while the Raman analysis showed that the conducting amorphous carbon increased on the surface of PP. The surface hardness and plane strain modulus of the PP decreased from 0.11 to 0.07 GPa and from 1.75 to 1.26 GPa, respectively, with respect to the Ar ion beam treatment time due to the surface nanostructures formed by the Ar ion beam.

Enhanced surface sensitivity in secondary ion mass spectrometric analysis of organic thin films using size‐selected Ar gas‐cluster ion projectiles

A size-selected argon (Ar) gas-cluster ion beam (GCIB) was applied to the secondary ion mass spectrometry (SIMS) of a 1,4-didodecylbenzene (DDB) thin film. The samples were also analyzed by SIMS using an atomic Ar(+) ion projectile and X-ray photoelectron spectroscopy (XPS). Compared with those in the atomic-Ar(+) SIMS spectrum, the fragment species, including siloxane contaminants present on the sample surface, were enhanced several hundred times in the Ar gas-cluster SIMS spectrum. XPS spectra during beam irradiation indicate that the Ar GCIB sputters contaminants on the surface more effectively than the atomic Ar(+) ion beam. These results indicate that a large gas-cluster projectile can sputter a much shallower volume of organic material than small projectiles, resulting in an extremely surface-sensitive analysis of organic thin films.

Nanosmoothing of single crystal diamond chips by 1 keV Ar+ ion bombardment

In this article the authors have studied the smoothing of diamond chips by irradiating them with 1 keV Ar ion beam at ion incident angles of 0°, 30°, 45°, 60°, and 80° with ion doses from 3.4×1018 to 6.8×1018 ions/cm2. They found that using ion dose of 6.8×1018 ions/cm2 at incident angles from 0° to 45°, the unprocessed surface (rms=0.14–1.2 nm) turned into ultrasmooth processed surface (rms=0.1 nm). Their results also confirmed the formation of ripples on diamond surface when the surface was irradiated with 1 keV Ar+ ion at incident angles of 60°–80°. They have also discussed the mechanism of smoothing and roughening of the surface by employing Bradley and Harper model and equations. These studies led to the understanding of the role of induced viscous flow in the smoothing process. Therefore, by choosing right conditions, 1.0 keV Ar+ ion beam machining can be employed to make diamond tools with nanofinished surface without any ripple effect.

Probing the heat affected zone by chemical modifications in femtosecond pulse laser ablation of titanium nitride films in air

A new approach is presented to quantify the so-called “heat affected zone” (HAZ) during femtosecond laser pulse processing. Ablation of titanium nitride (TiN) thin films (∼3 μm thickness) by multiple femtosecond laser pulses (τ=130 fs, λ=800 nm) in air environment was studied by means of two different surface analytical methods both being sensitive to chemical alterations at the surface. Scanning Auger electron microscopy was applied for a visualization of the spatial distribution of specific elements (Ti, O) within the laser-modified areas. The chemical state of the irradiated surface was revealed by complementary x-ray photoelectron spectroscopy. Both methods were used for a depth-profiling chemical analysis (tracking the elements Ti, N, O, and C) using an Ar-ion beam for surface sputtering. In a narrow laser fluence range slightly below the ablation threshold of TiN significant superficial oxidation can be observed leading to the formation of substoichiometric TiO2−x. At fluences above the ablation threshold, an increased titanium concentration is observed within the entire ablation craters. Following upon sputter removal the elemental distribution into the depth of the nonablated material, the results allow an estimation of the heat-affected zone for femtosecond laser ablation in air environment. According to our analyses, the HAZ extends up to a few hundreds of nanometers into the nonablated material.

Observation of carrier distribution in GaAs semiconductors using phase-shifting electron holography

Off-axis electron holography was used to map carrier distributions in GaAs semiconductors. After preparing cross-sectional transmission electron microscopy (TEM) specimens by a rotating-microprobe technique and a focused ion beam (FIB) system equipped with a low-voltage Ar ion beam for removing FIB damaged layers, we observed the different carrier concentration in GaAs specimens and evaluated the carrier diffusion at the interface between material with different carrier concentrations.

Constructing carbon nanotube junctions by Ar ion beam irradiation

Carbon nanotubes (CNTs) irradiated by Ar ion beams at elevated temperature were studied. The irradiation-induced defects in CNTs are greatly reduced by elevated temperature. Moreover, the two types of CNT junctions, the crossing junction and the parallel junction, were formed. And the CNT networks may be fabricated by the two types of CNT junctions. The formation process and the corresponding mechanism of CNT networks are discussed.

High aspect ratio wrinkles on a soft polymer

Instability of a stiff thin film attached to a compliant substrate often leads to the emergence of exquisite wrinkles with length scales that depend on the system geometry and applied stresses. These patterns have vast potential applications including in tissue engineering, flexible electronics and the semiconductor industry. However, one of the limiting factors in the usage of these patterns is the low amplitude/wavelength ratio that can be achieved using the current surface engineering techniques. Here, we present an effective method that allows the creation of wrinkles with an amplitude/wavelength aspect ratio as large as 2.5 on a soft polymer. In this method, first, the surface of a poly(dimethylsiloxane) (PDMS) is pre-patterned using an Ar ion beam. Then, an amorphous carbon film gets deposited on the pre-patterned polymeric surface using glancing angle deposition (GLAD). We show that the amplitude of the created patterns can be varied between several nm to submicron size by changing the carbon deposition time, allowing us to harness patterned polymeric substrates for a variety of applications. Specifically, we demonstrate a potential application of the high aspect ratio wrinkles for changing the surface optical band gap.

Evaluation of Ion Milled Soft X-ray Multilayer Mirrors for Reflection Wavefront Correction

Surface roughness and soft x-ray reflectance of soft x-ray Mo/Si multilayer mirrors ion-milled for physical optical reflection wavefront correction with 0.1 nm accuracy have been measured. The multilayer mirror was milled by Ar ion beam accelerated at 500 V using area-selected mask template with 10×10 mm2 opening. Milled surface at peripheral was rougher than that at center of milling area. Measured maximum roughness of 0.47 nm RMS would cause only under 0.01% reduction of reflectance by theoretical estimation. 44% peak reflectance of the ion-milled multilayer at λ=14.3 nm is practical enough for composing soft x-ray objectives such as Schwarzschild objective. These results prove that ion milling method is effective and gentle milling for precise figure error correction of soft x-ray multilayer mirrors.

Nano-fabrication processes for magnesium diboride

We compare the various nanowire fabrication processes for MgB2 ultra-thin films: Ar ion beam milling with or without a protective layer (Au and SiO2), an reactive ion etching (RIE) with fluorine-based gas, and a liftoff process using an Si/C bilayer mask. With Ar milling, we can fabricate nanowires down to 200nm-wide, but the superconducting properties degrade as the width decreases further. MgB2 can be etched by the fluorine-based RIE, but the etch rate is too slow for fabrication. The liftoff process gives the reliable and damage-free nanowires down to 100nm-wide.

The Morphology and Mechanical Properties of Polycarbonate/Acrylonitrile Butadiene Styrene Modified by Ar Ion Beam Irradiation

AbstractThis study examined the surface morphological evolution of polycarbonate and acrylonitrile butadiene styrene (PC/ABS) irradiated with an Ar ion beam using an ion beam system. PC was not affected by the Ar ion beam treatment at a lower ion beam treatment times but the ABS portion formed a foam‐like nanostructure at the surface. On the other hand, both PC and ABS formed nanostructures with length of 100 to 120 nm and a mean diameter of ≈35 nm at longer beam treatment times. The Raman and FTIR spectra revealed polymer chain scissioning. Nanoindentation showed that the hardness and elastic modulus of the PC/ABS decreases from 0.22 to 0.18 GPa and from 3.39 to 2.98 GPa, respectively with increasing Ar ion beam treatment time due to the surface nano‐structures formed by Ar ion beam.magnified image

Alignment of magnetic clusters in polymer using Ar ion beam

Free standing sheets of polyaniline and iron oxide (γ-Fe2O3)/polyaniline are synthesized by the solution casting method. The study describes the alignment of magnetic clusters in iron oxide/polyaniline nano-composite sheets using energetic argon (Ar) ions. The energy of the Ar ion was varied from 0.06 to 1.2 MeV and the fluence was varied from 1015 to 1017 ions cm−2. X-ray diffraction studies confirm that the single phase of γ-Fe2O3 has been retained in the composite sheets. The polyaniline free standing sheets do not show any structure. Clusters are observed in polyaniline/iron oxide nano-composite sheets using scanning electron microscopy. In addition to the dispersion of clusters, orientations of clusters have been observed. The observed increase in conductivity as a result of ion irradiation has been attributed to the formation of a carbonized phase and production of different chemical species. The magnetic properties of the composite samples, as a result of ion irradiation, remained unaffected.