Ion Beam Sputtering Technique Research Articles

Reduction of mechanical losses in ion-beam sputtered tantalum oxide thin films via partial crystallization

This study explores the impact of crystalline fraction on the mechanical losses of amorphous tantalum oxide (tantala, Ta2O5) thin films intended for gravitational wave detectors. We use ion beam sputtering technique to prepare a series of samples, which are then subjected to controlled thermal annealing to achieve varying degrees of crystallized fraction. The microscopic structure of the annealed samples is characterized by combining different analytical techniques. Our investigation reveals that the amorphous films comprise randomly distributed crystalline grains, whose density and average size depends on the duration of thermal treatment. To assess mechanical losses of the coatings, a gentle nodal suspension system is applied. Remarkably, a substantial reduction of approximately 20% in the coating’s mechanical loss angle with respect to annealed amorphous coatings is observed for samples exhibiting a crystalline fraction of around 5%. This improvement may lead to the definition of alternative thermal treatments to improve the mechanical performances of coatings for gravitational wave detectors or other highly sensitive optical experiments. However the reduction in mechanical losses comes at the expense of an increase in optical scattering. The possibility of reducing the optical losses to the level required by gravitational interferometers by modifying the grain size distribution via appropriate annealing treatments is discussed.

Improvement of high energy X-ray optical performance of W/Si supermirror by optimizing interface compounds using ultra-thin buffer layer

The high energy spectral properties of X-ray supermirrors are governed mainly by the interface diffusion and compound formation at the interfaces. Using ion beam sputtering technique, a set of W/Si periodic multilayers with C buffer layer (BL) and without C BL have been prepared and the effect of BL has been studied by grazing incidence specular X-ray reflectivity, diffused X-ray scattering and X-ray photoelectron spectroscopy. Using C BL at the W-on-Si interfaces, reduction of interface diffusion and minimization of WSix formation at the interfaces has been observed though signature of carbide formation has been noticed. Using the results an interface diffusion model has been proposed explaining the effect of C BL. Block method of X-ray supermirror design has been effectively used for reducing the number of layers of W/Si supermirror targeting the improvement of the performance. Finally, 36-layer W/Si supermirror with C BL and without C BL have been fabricated and the performance evaluated by reflectivity measurement using 25 keV synchrotron X-rays and cross sectional TEM measurements. This study has both technological implication in X-ray optical devices and also offers atomistic insight into the mechanism of improvement of the interface quality by application of ultra-thin buffer layer.

Studies on the structural and magnetic properties of PMMA/Ni nanocomposite system prepared by embedding Ni nanoparticles in the PMMA films

PMMA/Ni nanocomposite films have been prepared by embedding Ni nanoparticles and maintaining their different thickness (5–50 nm) in PMMA (polymethylmethacrylate) film matrix by using ion beam sputtering (IBS) technique. Grazing incidence x-ray diffraction (GIXRD) results reveal Ni is present in metallic form in the FCC phase. X-ray reflectivity (XRR) is used to measure the nominal thickness of the Ni nanoparticle layer. Surface morphology was studied using atomic force microscopes (AFM). SXAS (soft x-ray absorption spectroscopy) studies on PMMA/Ni nanocomposites were done using synchrotron radiation to understand the electronic structure of these films which reveals that Ni is present in metallic state confirming that PMMA as host matrix protects the magnetic Ni nanoparticles from external oxidation. The magneto-optical Kerr effect (MOKE) magnetometer and MOKE microscope were employed to study the magnetic properties and simultaneously record the real time evolution of magnetic domains at 0°, 45°, and 90° azimuthal angles. All films show soft ferromagnetic behaviour and all the films show isotropic behaviour except one with Ni nanoparticle layer thickness of 40 nm. MOKE micrographs witness the gradual growth of magnetic domains with increase in thickness of Ni nanoparticle layer. These PMMA/Ni nanocomposite films may be viewed as potential candidate for futuristic functional material.

Hydrogen and deuterium permeation on niobium coated by ultrathin Pd25%Ag for tritium recovery in EU DEMO

The hydrogen and deuterium permeation in pure niobium and niobium Pd25%Ag coated are measured using a permeation gas phase technique. The coating with different thicknesses, are deposited on Nb by a Dual Ion Beam Sputtering Technique. Measurements are performed in the temperature range of 573–723 K with hydrogen or deuterium driving pressures in the range 1.0⋅102−1.2⋅104 Pa (1 to 120 mbar). This work highlights how PdAg-coated Nb membranes can be fruitfully rated in the design of tritium recovery plants where niobium pipes for lead lithium are under consideration. Ultra-thin PdAg coatings mitigate the effects of the oxide in reducing of hydrogen permeation through the niobium walls.

Structural and Magnetic Properties of Ni Nanoparticles Embedded in Vinyl Polymer Nanocomposite Films

Ni nanoparticles layer of nominal thickness in the range of 5–40[Formula: see text]nm were deposited on polyvinyl alcohol (PVA) film by using the ion beam sputtering (IBS) technique. PVA films were made on a quartz substrate by the solution casting technique. Grazing incidence X-ray diffraction (GIXRD) results reveal Ni is present in a metallic form in the FCC phase. AFM shows that roughness increases with increase in thickness of Ni layer and corresponding MFM images of magnetic domains were recorded. Soft X-ray absorption spectroscopy (SXAS) studies on the PVA/Ni nanocomposites films were recorded using synchrotron radiation. This study is used to study the electronic structure of the as-prepared nanocomposite films and reveals that Ni nanoparticles are present in their metallic form. Magnetic properties were measured using the magneto-optical Kerr effect (MOKE) magnetometer and the films were found to be magnetically soft with higher value of coercivity at lower thickness of Ni nanoparticles layer. The results of magnetic studies are discussed in light of the microstructure and morphological features of PVA/Ni nanocomposite films. The PVA/Ni nanocomposites showed interesting anisotropic magnetic behavior; thus the investigative results may be useful for the development of futuristic flexible functional magnetic material system.

Deposition of titanium carbide catalytic films on vanadium foils by ion beam sputtering for hydrogen separation and purification

Titanium carbide (TiC) catalytic films were deposited on vanadium (V) foils by ion beam sputtering (IBS) technique for hydrogen purification. The effect of sputtering temperature in the IBS process on the phase structure and catalytic property of the TiC catalytic films and the hydrogen permeation performance of TiC/V composite membranes was investigated. The carbon vacancy density of TiC films increases with the sputtering temperature, resulting in increasing catalytic property of TiC films and hydrogen permeation performance of TiC/V composite membranes. At sputtering temperature of 400 °C, the TiC/V composite membranes exhibit highest hydrogen permeability (∼9.5 × 10−8 mol H2 m−1 s−1 Pa−0.5) at 650 °C and excellent stability during the thermal cycles at 450–650 °C.

Atom deposition and sputtering at normal incidence simulated by the Frenkel-Kontorova chain.

The impact of a molecule of N atoms with a speed of v_{0} on the free end of the Frenkel-Kontorova chain is numerically simulated. Depending on the values of N and v_{0}, different scenarios of the molecule-chain interaction are observed. Molecules with low speed stick to the chain. At somewhat higher speeds, the molecules bounce off the chain. Further increase in v_{0} results in bouncing off a molecule larger than the incident one. At even higher speed, bouncing of the molecule off the chain takes place simultaneously with the formation of a supersonic crowdion (antikink) propagating along the chain. A very high collision velocity leads to the sputtering of atoms from the chain and the formation of single and multiple supersonic crowdions. Interestingly, the sputtering yield Y as the function of v_{0} demonstrates a nonmonotonous dependence. This is explained by the fact that supersonic crowdions can have a discrete set of propagation velocities. When v_{0} is such that supersonic crowdions are effectively excited, the latter transfer energy deep into the chain, and the sputtering is minimal. For some v_{0} ranges, the formation of supersonic crowdions is suppressed. In these cases, the energy transferred from the impact of the molecule to the chain is spent mainly on the sputtering of atoms. The results obtained qualitatively explain the physics of bombardment of a crystal surface by atomic clusters with applications in physical vapor deposition, ion implantation, ion-beam sputtering, and similar experimental techniques.

Influence of metal codeposition on the growth and orientation of nanoripple structure during ion bombardment

Surface engineering to tune the surface characteristics for the enhancement of a system is an emerging area of research in terms of its immense technological applications and basic scientific understanding. The ion beam sputtering technique in combination with cosputtered material deposition to form various structures is found to be a very effective bottom-up approach to modify the surface morphology of a material. In this paper, a theoretical model is developed for ripple evolution of a flat elemental surface which is subjected to erosion by ion bombardment at off-normal incidence with concurrent deposition of some impurity or foreign materials. The orientation of the ripple wave vector thus produced exhibits a directional dependence behavior on the projection of both the ion beam and the foreign elements on the surface. The compound formation at the near-surface depth is considered to be the key assumption for inducing such patterns on the surface. The theoretical prediction is realized in the experimental work demonstrated herein. Stainless steel is used as a cosputtering target during irradiation of Si at ${30}^{\ensuremath{\circ}}$ incidence by a low-energy ${\text{Ar}}^{+}$ ion beam. The ripples that so emerge possess a wave vector lying oblique to the direction of the ion beam and impurity. The development of such morphological instability is attributed to the reaction between Fe and Si, which gives rise to a compound with an erosion rate lower than that of Si. Thus, the formation of the ${\text{FeSi}}_{2}$ bond, which is interpreted as being a crucial criterion for pattern evolution, agrees well with the theory, making it quite efficient and widely acceptable.

Influence of Deposition Conditions on Properties of Ta2O5 Films Deposited by Ion Beam Sputtering Coating Technique

Investigation of deposition conditions on structural, optical, and surface properties of Tantalum pentaoxide (Ta2O5) thin films deposited without assisted ion beam (Single Ion Beam Sputtering technique, SIBS) and with assisted ion beam (Dual Ion Beam Sputtering technique, DIBS) is carried out. For both SIBS and DIBS identical coating process conditions are applied for deposition of Ta2O5 films onto highly polished and clean, fused silica substrates. Estimation of deposition rates of Ta2O5 with identical beam energies and coating chamber conditions is done. Benefits of O2 assist beam on the behavior of structural, optical, and surface properties of thin films deposited are studied. The films are characterized with an ellipsometer, optical profilometer, XRD, FE-SEM, and XPS techniques to bring the merits films coated of Ion Beam Sputtering deposition with and without assist Ion Beam. Configuration of ion sources and targets in the coating chamber for DIBS of oxide targets is carried out in the present work are useful for multi-layer coatings for high reflectivity mirrors for electro-optical instruments like ring laser-based rotation sensors.

Dielectric properties, polarization process, and charge transport in granular (FeCoZr)x(Pb(ZrTi)O3)(100−x) nanocomposites near the percolation threshold

This paper presents the research of dielectric properties of (FeCoZr)x(Pb(ZrTi)O3)(100−x) granular metal–dielectric nanocomposites below the percolation threshold. Tested materials have been prepared by using the ion beam sputtering technique in the atmosphere of argon and oxygen. The impedance spectroscopy method has been used to investigate the polarization processes and dielectric relaxation mechanism in the granular nanocomposites. AC measurements in the frequency region of 50 Hz to 1 MHz and measuring temperature range of 81–293 K have been performed. Interfacial, in the low frequency region, and dipolar, in intermediate and high frequency regions, types of polarization processes were observed. The interfacial relaxation process testifies to charge accumulation at the interfaces (grain boundaries) between conductive nanoparticles surrounding an insulative matrix, as well as the space charge region around the contact area between the measurement probes and tested sample. Dipolar polarization corresponds to electric dipole formation after applying to the material an external electric field. The conduction mechanism in the tested material is considered to be hopping carrier exchange and takes place between metallic phase nanograins. It corresponds to the exponential frequency dependence of conductivity. The relaxation mechanism in the (FeCoZr)x(Pb(ZrTi)O3)(100−x) layer has been estimated as a near-Debye process with relaxation time distribution. The nanocomposite exhibits dielectric type and capacitive characteristics in the whole measuring frequency range.

Qualitative Analysis of the Valence and Conduction Band Offset Parameters in FeNiO/CuNiO Bilayer Film Using X‐Ray Photoelectron Spectroscopy

The valence and conduction band offset in FeNiO/CuNiO bilayer film are studied utilizing X‐ray photoelectron spectroscopy and UV–vis spectroscopy. The bilayer film is grown on Si substrate employing ion beam sputtering technique using a mixture of argon and oxygen gases at 25% oxygen partial pressure. From the precise knowledge of the valence band maxima energies and core‐level energy positions in the single‐layer film and the corresponding shifts in the bilayer film, the valence and conduction band offsets are estimated to be 0.8 and 0.3 eV, respectively. From the computed band offset data, a type‐I band alignment is identified at the interface of the grown bilayer film, which facilitates the knowledge of carrier transport mechanism and is highly attractive for the realization of efficient room‐temperature optoelectronic device.

Optical properties of Ni metal nanoparticles embedded poly (vinyl alcohol) films

This paper reports the effect of Ni layer thickness on the optical properties of the PVA/Ni nanocomposite films prepared by embedding Ni nanoparticles into the PVA (polyvinyl alcohol) film matrix using ion beam sputtering technique. UV–Vis-NIR spectra have been used to determine the optical parameters like absorption bands, absorption edge, transmission, bandgap, refractive index (RI), extinction coefficient and optical conductivity. As observed, all the above optical parameters were found to have changed remarkably on incorporation of Ni nanoparticles in the PVA film; for example, indirect band gap reduced from 5.01 to 4.38 eV, and RI increased from 1.21 to 10.04.

Investigations on structural and magnetic properties of PET/Co nanocomposite film prepared by ion beam sputtering

Over the years, polymer-metal nanocomposites have been extensively investigated due to their potential ability to produce materials with novel mechanical, electronic, optical and magnetic properties for technological applications. In the current paper, we present the studies on cobalt (Co) nanoparticles embedded polyethylene terephthalate (PET) by ion beam sputtering technique. Co nanoparticle layer (10 nm thick) was deposited onto PET substrate by ion beam sputtering. Grazing incidence x-ray diffraction results reveal that the Co is present in the metallic form in the FCC phase. MOKE studies reveal the anisotropic behavior of PET/Co nanocomposite film. The results are discussed in the paper.

Surface and interface characterization of Ru/C/Ru trilayer structure using grazing incidence X‐ray reflectivity and X‐ray fluorescence

In 8‐ to 20‐keV photon energy region, ruthenium and carbon thin films are used in multilayer monochromators. In the present study, this material combination is explored for X‐ray waveguide applications in hard X‐ray region. The structural parameters (thickness of each layer) of Ru/C/Ru waveguide structure are optimized to get maximum intensity enhancement of fundamental mode inside carbon guiding layer. A sample with optimized structural parameters is deposited using ion beam sputtering (IBS) technique and characterized using X‐ray reflectivity (XRR) and grazing incidence X‐ray fluorescence (GIXRF) techniques. The analysis suggests that the density of bottom Ru layer and carbon guiding layer is close to bulk density (~97% for Ru and ~95% for carbon), whereas density of top Ru layer is slightly lower (~93% of bulk density). A ~10% of thickness variation in top cladding layer along with marginal change in layer density deteriorate field enhancement in TE0 mode by more than three times. Effect of thickness and density variation on waveguide (Ru [7 nm]/C [18 nm]/Ru [20 nm]) performance is discussed.

Evolution of the interface microstructure of short-period Cr/Ti multilayers with increase in number of bi-layers

Evolution of interface microstructure with addition of more number of layers has been investigated on Cr/Ti multilayer which is important for application as a mirror or monochromator in the “water window” soft X-ray spectral regime. Two sets of Cr/Ti multilayers at moderate and low bi-layer thickness regime have been prepared for this purpose using Ion Beam Sputtering technique. In one set, Cr/Ti multilayer with 25, 50, 60 and 100 numbers of bilayers with moderate bi-layer thickness of 3.8 nm have been deposited. In another set, four samples each having low bilayer thickness of 2.4 nm with 25, 50, 75 and 100 number of bi-layers have been prepared and the multilayers have subsequently been characterized with Specular X-ray reflectivity and diffuse X-ray scattering measurements at grazing incidence with hard X-rays. It is observed that cumulative effect of interface imperfections became more pronounced with increasing number of bilayers resulting in continuous increase in the interface width in both the thickness regimes; however, its evolution is not exactly same for the two sets of samples. Diffuse X-ray scattering result reveals that for the first set of samples, interface imperfections are dominated by interface roughness with no change in the interface diffusion with increase in number of layers, while for the second set, both interface roughness as well as interface diffusion contribute towards the cumulative accumulation of interface imperfections which is also confirmed by cross-sectional Transmission Electron Microscopy. Finally, performance of the multilayers in water window regime has been checked by soft X-ray reflectivity measurements using synchrotron radiation. The above results have direct implication in utilisation of these multilayers over a wide bi-layer thickness regime required to cover the full ‘water-window’ spectrum.

Surface Physical Properties of Ion Beam Sputtered Copper Thin Films on Poly Tetrafluoroethylene

In this study thin copper (Cu) films are deposited on poly tetrafluoroethylene (PTFE) substrate using ion beam sputtering technique. The films are characterized using Raman spectroscopy, UV–VIS spectroscopy and atomic force microscope (AFM) techniques. The Raman spectrum shows some decrease in the intensities of Raman bands for Cu/PTFE film than pristine PTFE. UV–VIS transmittance spectra display that the optical transmission reduces from ~75% for pristine PTFE to ~0.20% after 60 min of deposition due to Cu nanoparticles dispersed in PTFE. The surface roughness is increased from 39.4 nm for PTFE to 75.9 nm, while the adhesion force is increased from 9.6 nN to 14.7 nN and Young’s modulus is enhanced from 0.58 GPa to 1.46 GPa after 40 min of Cu deposition time. The DC electrical conductivity at an applied voltage of 200 V is improved from 3.88 × 10–8 S.cm−1 for PTFE to 5.3 × 10–8 S.cm−1 after 60 min of deposition at room temperature. The fabricated Cu/PTFE films exhibit excellent surface properties, which demote that Cu/PTFE films could serve as a low cost material for a broad range of electrical and charge storing devices.

Impact of ferromagnetic layer thickness on the spin pumping in Co60Fe20B20/Ta bilayer thin films

We report the tuneable spin angular momentum transfer (spin pumping) from Co60Fe20B20 (CFB) amorphous alloy into the Ta heavy metal nanolayers. All the films are grown on Si (100) substrate at room temperature using ion-beam sputtering technique. Structural studies reveal that the grown Ta films over amorphous CFB are crystalline even at ultrathin regime. The bilayers possess very low interface roughness (< 0.5 nm) and are continuous throughout the thickness range. Comparative analysis of the spin pumping in CFB (4, 6 and 8 nm) as a function of the Ta thickness (vary from 1 to 10 nm in step of 1 nm) has been performed employing ferromagnetic resonance (FMR) spectroscopy. It is observed that the effective damping increase exponentially with the increase of Ta, (i.e. follows ballistic spin transport) in two series of CFB (4 nm)/Ta (0–10 nm) and CFB(6 nm)/Ta (0–10 nm) bilayers, which is characteristic of normal spin pumping. However, the anomalous behaviour has been observed for CFB (8 nm)/Ta (0–10 nm) bilayer series where the spin current generated in Ta with the thicker CFB behaves oppositely. The results demonstrate the strong dependence of ferromagnet thickness on the spin pumping into the Ta nanolayers. This study paves the way to choose suitable ferromagnetic layer thickness for spin current-induced switching applications in spintronics.

Comparison of high temperature growth versus post-deposition in situ annealing in attaining very low Gilbert damping in sputtered Co2FeAl Heusler alloy films

In this work, a detail study on the effectiveness of high substrate temperature (TS) during deposition versus in situ annealing of the films at high temperature (TA) after sputtering at room-temperature is compared with an objective to obtain Heusler alloy thin films of Co2FeAl (CFA) having optimally low αint (with an upper bound of 1.75 × 10-3) and 12–17% smaller MS by employing ion beam sputtering technique and Si(100) as substrates for current induced magnetization switching application. In each of the two series of CFA films, prepared with different choice of TS and TA (lying in 300–773 K range) were explored for optimally tailoring their structural, static and dynamic magnetization properties. Structural study revealed that although all the CFA films were polycrystalline but the post-deposition annealed films were structurally optimal with higher density (6.36 ± 0.09 g/cm3) and lower interface roughness (0.48 ± 0.03 nm) compared to the CFA films grown at high TS (6.23 ± 0.06 g/cm3, 0.61 ± 0.01 nm). In plane field-angle dependent longitudinal magneto optical Kerr effect (L-MOKE) study revealed the existence of a coupling between the weak uniaxial and biaxial magnetic anisotropies present in these films, attributed to the employed deposition geometry. Ferromagnetic resonance (FMR) spectroscopy measurements, performed in both the geometries - in-plane as well as out of plane, revealed a lowest value of 1.19 (±0.08) × 10-3 of αint in the film post-annealed at 773 K. In addition, the observed non-linear relation between the αint and the dynamical ‘g’-factor suggests that the contribution of spin orbit interaction to the damping is far less compared to the damping contribution from the DOS present near the Fermi level. It is remarkable to note that the as-grown CFA films sputtered at room temperature exhibited a record lowest value of 1.73 (±0.09) × 10-3 of αint. Attainment of such small value of Gilbert damping and having moderate magnetization in high spin polarized Co2FeAl Heusler films sputtered on the Si (100) substrate opens up their great application potential in future spintronics devices.

Simple and effective cleaning method for RuO2 nanosheet films for flexible transparent conducting electrodes

A critical and practical issue in employing low dimensional nanomaterials as transparent conducting electrodes (TCEs) is the simple and effectual cleaning of the nanomaterials; the presence of contaminants increases the contact resistance at the interface region in practical applications. In this study, various cleaning methods are examined to remove surface contaminants on RuO2 nanosheets (NSs), which are the promising materials for TCEs. The Ar gas cluster ion beam (GCIB) sputtering technique can effectively remove organic surface contaminants, although it has critical drawbacks in the mass production. The simple deionized water treatment can provide satisfactory cleaning performance, which is comparable with that of the Ar GCIB sputtering method. Other methods such as solution-based treatments that use ethanol and chloroform and the heating method do not provide a comparable cleaning performance. The conductive atomic force microscopy demonstrates highly increased conductivity of water-cleaned RuO2 NS films at the nanoscale. This study proposes a practical method for the cleaning of RuO2-based nanomaterials for their application as TCEs and emphasizes their significance of the cleaning process to achieve a higher performance for TCEs based on low dimensional nanomaterials.

Enhanced dielectric properties of flexible Cu/polymer nanocomposite films

This research studied the comprehensive dielectric properties of copper (Cu)/polyethylene terephthalate (PET) and copper/polytetrafluoroethylene (PTFE) composite films under the influence of copper nanoparticle (CuNP) sputtering time. Copper thin film was grown on flexible PET and PTFE using the ion beam sputtering technique. X-ray diffraction confirmed that CuNPs had been successfully synthesized on the polymer substrate. The electrical conductivity σ AC of the films was measured using alternating-current conductivity impedance in the frequency range of 102–106 Hz. It increased from 1.2 × 10−6 S/cm for PET to 9.65 × 10−7 S/cm for 75 min copper/PET and from 6.38 × 10−7 S/cm for PTFE to 9.24 × 10−7 S/cm for 75 min copper/PTFE. The dielectric constant ε′ increased from 0.62 for pristine PET to 1.19 for 25 min copper/PET and from 1.88 for pristine PTFE to 2.25 for 25 min copper/PTFE at an applied frequency of 105 Hz. In addition, other parameters – namely, dielectric loss ε″, dielectric modulus m and dielectric tangent constant tan δ – were investigated. The comprehensive results showed that the dielectric properties of flexible PET and PTFE polymers improved due to the deposited conductive CuNPs. Flexible copper/PET and copper/PTFE composite films are promising as dielectric substrates for modern electronic applications that can resist hard environments and have long lifetimes.