Rutherford Backscattering Spectrometry Studies Research Articles

Formation of partially embedded Au nanostructures: Ion beam irradiation on thin film.

The Au partially embedded nanostructure (PEN) is synthesized by ion irradiation on an Au thin film deposited on a glass substrate using a 50 keV Ar ion. Scanning electron microscopy results show ion beam-induced restructuring from irregularly shaped nanostructures (NSs) to spherical Au NSs, and further ion irradiation leads to the formation of well-separated spherical nanoparticles. Higuchi's algorithm of surface analysis is utilized to find the evolution of surface morphology with ion irradiation in terms of the Hurst exponent and fractal dimension. The Au PEN is evidenced by Rutherford backscattering spectrometry and optical studies. Also, the depth of the mechanism behind synthesized PEN is explained on the basis of theoretical simulations, namely, a unified thermal spike and a Monte Carlo simulation consisting of dynamic compositional changes (TRIDYN). Another set of plasmonic NSs was formed on the surface by thermal annealing of the Au film on the substrate. Glucose sensing has been studied on the two types of plasmonic layers: nanoparticles on the surface and PEN. The results reveal the sensing responses of both types of plasmonic layers. However, PEN retains its plasmonic behavior as the NSs are still present after washing with water, which demonstrates the potential for reusability. RESEARCH HIGHLIGHTS: Synthesis of PENs by ion irradiation Utilization of Higuchi's algorithm to explore the surface morphology. Unified thermal spike and TRIDYN simulations being used to explain the results. Glucose is only used as a test case for reusability of substrate.

Influence of swift heavy ions on aluminum thin films

Controlled ion beam irradiation of the target material results in material modification as the ions give away their energy to the material, either by interacting with electrons, a process designated as electronic energy loss (Se) or by interacting with the nuclei, known as nuclear energy loss (Sn). As a consequence, changes occur in the structural and electronic properties of the material that need to be systematically investigated. In this work, 25 nm thin Aluminium films were deposited over a silicon substrate and subjected to 100 MeV O7+ and 100 MeV Si7+ ion irradiation with ion fluences varying from 1 × 1011 to 1 × 1013 ions/cm2. The swift heavy ion (SHI) irradiated and pristine films are then characterised using Glancing Incident X-Ray Diffraction (GIXRD), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM), to study the effects of the irradiation with different ion species, having a large variation in Se and Sn. The GIXRD analysis revealed the change in crystallinity along with the change in crystallite size as compared to the pristine film. RBS studies indicate no change in the composition as there is negligible evidence of electronic sputtering. AFM shows that the irradiation of the film results in restructuring, with the particle size distribution shifting towards a lower value, while the surface roughness reduces from 2.8 ± 0.24 nm for the pristine surface to 1.35 ± 0.03 nm for O7+ and 1.63 ± 0.27 nm for Si7+ ion irradiated surfaces at the fluence of 1 × 1013 ions/cm2. SEM results confirm grain fragmentation as the irradiation proceeds, and also reveal the decrease in roughness values.

Surface engineering of Pt thin films by low energy heavy ion irradiation

A systematic study of nanostructuring of platinum (Pt) thin films of different thicknesses deposited on silicon substrates has been performed under the irradiation of low energy Kr+ ions. First, Pt thin films of various thicknesses (~2–6 nm) were grown on the Si substrates, which were subsequently irradiated with 100 keV Kr+ ions as a function of ion fluence. The resultant surface modifications after irradiation are studied by atomic force microscopy (AFM), which reveals that higher ion fluence and larger thickness of Pt thin films are more favorable for nanostructures formation. Surface growth features have been analysed using kinetic roughening of surfaces. Scaling components (roughness and growth components) reveals that the sputtering is the principal factor causing surface nanostructuring in platinum (Pt) thin films. For higher thicknesses ion beam induced adatoms diffusion is favoring the surface roughning. The mechanism of nanostructuring on different thicknesses of Pt films has been analyzed using Rutherford backscattering spectrometry (RBS) study and SRIM-TRIM calculations. For higher thickness of Pt film, irradiating projectile ions results in high energy deposition in the film. Thus, thickness-dependent sputtering yield and adatoms surface diffusions play an important role in nanostructuring of Pt thin films under ion irradiation.

Single phase formation of Fe-doped directional ZnO nanorod films: Study of cluster formation by complex impedance spectroscopy and removal of metal clustering by swift heavy ion irradiation

Room temperature ferromagnetism in Cluster free films of vertically aligned Fe-doped ZnO nanorods have been developed. Controlled doping was carried out by iron (Fe) ion-implantation. The metal clusters formed during implantation are dissolved into the ZnO matrix by swift heavy ion irradiation of Fe-doped films using 200 MeV sliver beam. The origin of ferromagnetism in the Fe-doped ZnO nanorods is investigated. Raman spectra show shift of ZnO phonon mode to lower frequencies due to substitution of Zn by Fe. Rutherford backscattering spectrometry (RBS) studies are carried out to estimate the film thickness and concentration of Fe-ions as well as to establish the fact that the Fe-ions are placed in the ZnO matrix. We demonstrate cluster free nature of our nanorods using magnetization versus temperature analysis and the complex impedance spectroscopic studies. Dispersion of implanted Fe and lattice defects such as oxygen vacancies are attributed to be the source of ferromagnetism in nanorods.

Surface characteristics of nitrogen ion implanted CR-39 polymer: RBS studies

This paper investigates the surface characteristics of nitrogen ion implanted CR- 39 polymer. The specimens were implanted with 100 keV N+ beam to various fluences of 1 × 1015, 1 × 1016 and 2 × 1016 ions cm−2. The ion implantation induced modifications in these specimens were analyzed by Rutherford Backscattering Spectrometry (RBS) and UV- Visible spectroscopy. RBS studies reveal that the structure of the virgin CR-39 specimen has been modified completely after N+ implantation. The spatial distribution in the form of carbonization, projected range, retained dose and atomic concentration of implanted nitrogen have been estimated using RBS spectra. RUMP analysis revealed that for the implanted specimen at fluence 2 × 1016 N+ cm−2, the carbon concentration increases from 32 at.% to 43 at.% and oxygen concentration from 19 at.% to 26 at.% respectively near the surface. This increase in the concentration of carbon points towards the carbonization in the implanted layers. Furthermore, UV–Visible transmission spectra demonstrate that for higher fluences, almost complete UV region is blocked; making CR-39 a viable functional material for UV blocking devices.

Structural, optical and transport studies of nanocomposite SnOx thin films grown by DC sputter deposition and post-annealing

In this paper, we report on the systematic variation in structural, optical and transport properties of SnOx films prepared by DC sputter deposition followed by post-deposition annealing in air for 15 min each, firstly at 200 °C, and subsequently at 250, 275 and 300 °C. The formation of Sn rich SnO crystalline phase with annealing at 200 °C, its increase with annealing at 250 °C due to oxidation of Sn, and its partial decomposition to amorphous SnO2 phase upon annealing at and above 275 °C, were identified by x-ray diffraction and Raman spectroscopy studies. The bandgap value was 2.63 eV for the film with highest SnO crystalline phase obtained with annealing at 250 °C, and it was higher at 2.67 eV and 2.71 eV for films subsequent annealed at 275 °C and 300 °C, respectively. The transmittance of the films in the 400–650 nm wavelength range increased from a minimum of 0.15 to a maximum of 0.82 upon increment in annealing temperature. Rutherford backscattering spectroscopy study revealed an increase of oxygen in the films with annealing. Transport measurements performed on the annealed films show that they exhibit n-type conductivity with resistivity in the 1.05 − 0.01 × 10+1 Ω cm range and a very weak photo-response to visible light. Our results indicate the potential use of the n-type SnOx films as high-resistivity transparent (HRT) buffer layer in flexible solar cells.

Atomic layer deposition of HfO2 using HfCp(NMe2)3 and O2 plasma

HfO2 thin films were prepared by plasma-enhanced atomic layer deposition using a cyclopentadienyl-alkylamido precursor [HfCp(NMe2)3, HyALD™] and an O2 plasma over a temperature range of 150–400 °C at a growth per cycle around 1.1 Å/cycle. The high purity of the films was demonstrated by x-ray photoelectron spectroscopy and elastic recoil detection analyses which revealed that by increasing the deposition temperature from 200 to 400 °C, the atomic concentrations of residual carbon and hydrogen reduced from 1.0 to <0.5 at. % and 3.4 to 0.8 at. %, respectively. Moreover, Rutherford backscattering spectroscopy studies showed an improvement in stoichiometry of HfO2 thin films with the increase in deposition temperature, resulting in Hf/O ratio close to ∼0.5 at 400 °C. Furthermore, grazing incidence x-ray diffraction measurements detected a transition from amorphous at the deposition temperature of 300 °C to fully polycrystalline films at 400 °C, consisting of a mixture of monoclinic, tetragonal, and cubic phases. Finally, the surface morphology and conformality of HfO2 thin films studied by atomic force microscopy and transmission electron microscopy are also reported.

Growth and characterization of Au nanoparticles embedded In2O3 composite films

Au nanoparticles embedded In2O3 thin films (In2O3:Au) were grown by DC reactive sputtering method in three different target configurations. Presence of Au in In2O3 matrix was confirmed by glancing angle X-ray diffraction (GXRD) and transmission electron microscopy (TEM). Crystallite sizes of Au were obtained by Debye-Scherrer formula from GXRD data. Localized surface plasmon resonance was observed for In2O3:Au samples from optical absorption measurement at peak value of ~550nm and inferred red shift of resonance peak towards the increasing crystallite size. Rutherford backscattering spectrometry (RBS) studies of selected samples on Si substrate showed minor In diffusion and absence of Au diffusion into the Si substrate. X-ray photoelectron spectroscopy (XPS) studies revealed that the chemical state of Au is neutral. The samples with high Au content exhibited persistent photoconductivity due to the sub band gap absorption indicating the introduction of sub band gap trap levels in In2O3.

Ion beam induced optical and surface modification in plasmonic nanostructures

In present work, ion irradiation induced nanostructuring has been exploited as an efficient and effective tool for synthesis of coupled plasmonics nanostructures by using 1.2MeV Xe ions on Au/ZnO/Au system deposited on glass substrate. The results are correlated on the basis of their optical absorption, surface morphologies and enhanced sensitivity of evolved phonon modes by using UV Visible spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy (RS), respectively. Optical absorbance spectra of plasmonic nanostructures (NSs) show a decrease in band gap, which may be ascribed to the formation of defects with ion irradiation. The surface morphology reveals the formation of percolated NSs upon ion irradiation and Rutherford backscattering spectrometry (RBS) study clearly shows the formation of multilayer system. Furthermore, RS measurements on samples are studied to understand the enhanced sensitivity of ion irradiation induced phonon mode at 573cm−1 along with other modes. As compared to pristine sample, a stronger and pronounced evolution of these phonon modes is observed with further ion irradiation, which indicates localized surface plasmon results with enhanced intensity of phonon modes of Zinc oxide (ZnO) material. Thus, such plasmonic NSs can be used as surface enhanced Raman scattering (SERS) substrates.

Metal-organic chemical vapour deposition of lithium manganese oxide thin films via single solid source precursor

AbstractLithium manganese oxide thin films were deposited on sodalime glass substrates by metal organic chemical vapour deposition (MOCVD) technique. The films were prepared by pyrolysis of lithium manganese acetylacetonate precursor at a temperature of 420 °C with a flow rate of 2.5 dm3/min for two-hour deposition period. Rutherford backscattering spectroscopy (RBS), UV-Vis spectrophotometry, X-ray diffraction (XRD) spectroscopy, atomic force microscopy (AFM) and van der Pauw four point probe method were used for characterizations of the film samples. RBS studies of the films revealed fair thickness of 1112.311 (1015atoms/cm2) and effective stoichiometric relationship of Li0.47Mn0.27O0.26. The films exhibited relatively high transmission (50 % T) in the visible and NIR range, with the bandgap energy of 2.55 eV. Broad and diffused X-ray diffraction patterns obtained showed that the film was amorphous in nature, while microstructural studies indicated dense and uniformly distributed layer across the substrate. Resistivity value of 4.9 Ω·cm was obtained for the thin film. Compared with Mn0.2O0.8thin film, a significant lattice absorption edge shift was observed in the Li0.47Mn0.27O0.26film.

Swift heavy ion irradiation induced interactions in the UMo/X/Al trilayer system (X = Ti, Zr, Nb, and Mo): RBS and μ-XRD studies

Uranium–molybdenum (UMo) alloy embedded in an Al matrix (UMo/Al) has been considered as a promising candidate for fuel conversion of research reactors. A modified system with a diffusion barrier, UMo/X/Al trilayer (X=Ti, Zr, Nb, and Mo), has been investigated in order to suppress interdiffusion between UMo and the Al matrix. The trilayer was tested by swift heavy ion irradiation, followed by Rutherford backscattering spectroscopy (RBS) and X-ray micro-diffraction (μ-XRD). Atomic mixing at the interfaces was resolved by RBS, indicating that Ti interacts strongly with UMo while Zr does with Al. μ-XRD revealed the formation of intermetallic AlX compounds which can detain further atomic mixing. However, Ti and Zr as diffusion barrier can be controversial because their presence might lead to γ-UMo decomposition. This study presents the effectiveness of diffusion barriers and the irradiation-induced phase impacting on the properties of the UMo/X/Al trilayer.

Synthesis of embedded Au nanostructures by ion irradiation: influence of ion induced viscous flow and sputtering

The ion-irradiation induced synthesis of embedded Au nanoparticles (NPs) into glass from islands of Au on a glass substrate is studied in the context of recoiling atoms, sputtering and viscous flow. Cross sectional transmission electron microscopy studies revealed the formation of Au NPs embedded in the glass substrates by the 50 keV Si− ion irradiation of irregularly shaped Au nanostructures on the glass surfaces at a fluence of 3 × 1016 ions/cm2. The depth profiles of Au in the samples were obtained from high-resolution Rutherford backscattering spectrometry studies. The results from TRIDYN simulation reveal the role of various ion-induced processes during the synthesis of the embedded Au NPs, viz. sputtering and recoiling atoms. Simulation and experimental results suggest that the viscous flow is one of the major factors that are responsible for the embedding of Au nanoparticles into the glass substrate.

Photoluminescence investigation of erbium-implanted in KTiOPO4 and RbTiOPO4

KTiOPO4 (KTP) and RbTiOPO4 (RTP) crystals have been implanted with 500keV Er ions at a dose of 3×1015ions/cm2 with the aim of optically doping the material in the near surface region. The sample was annealed at 500°C for 90min in oxygen atmosphere after implantation. Photoluminescence (PL) and Rutherford backscattering spectrometry studies were performed on the as-implanted samples before and after annealing. 1.54μm photoluminescence emission was observed at both room-temperature and low-temperature in KTP without any annealing. After annealing luminescence intensity is improved at 12K and photoluminescence quenching were found at room temperature for both samples. The reasons are discussed in the paper.

Polymerized nanoporous titania surfaces: modification of cell adhesion by acrylic acid functionalization

Nanoporous titania (nPTI) has been prepared by electrochemical processes and functionalized by photochemical activation of condensed acrylic acid vapors (AcAc). The nPTI surfaces obtained after electrochemical etching in HF electrolytes at constant potential consisted of nanotube disordered arrays. Elastic recoil detection and Rutherford backscattering spectroscopy studies confirm the presence of an in-depth carbon based layer, previous to the AcAc polymerization. The subsequent AcAc functionalization affected only a few molecular monolayers since the process did not modify the nPTI structure observed by scanning electron microscopy. In fact, X-ray photoelectron spectroscopy confirms the presence of a carboxylic group contribution in the C 1s core-level spectrum only after AcAc polymerization of nPTI. Such results are of relevance for cellular attachment of human mesenchymal stem cells, whose adhesion onto nPTI is drastically enhanced after AcAc biofunctionalization.

Investigation of swift heavy ion-induced mixing in metal/polymer systems

We have investigated swift heavy ion-induced mixing in Ni/Teflon and Au/Teflon systems using 120 MeV Au ions. Our earlier studies showed that the Ni/Teflon system exhibits strong interface mixing, as determined by Rutherford backscattering spectrometry (RBS). In the present work, the Ni/Teflon system is further studied by scanning electron microscopy and Fourier transform infrared spectroscopy. Moreover, RBS studies are extended to demonstrate interface mixing in the Au/Teflon system. The observed mixing is explained on the basis of the chemical activeness (or reactivity) of the metal/polymer systems leading to a chemical reaction. The chemical reaction occurs in the hot zone around the ion path between the Ni and reactive polymer species. Thermodynamic property bond dissociation energy has been taken into account for the reactivity of the systems.

RBS, XRD, Raman and AFM Studies of Microwave Synthesized Ge Nanocrystals

ABSTRACTGe nanocrystals embedded in silica matrix have been synthesized on Si substrate by co-sputtering of SiO2 and Ge using RF magnetron sputtering technique. The as-deposited films were subjected to microwave annealing at 800 and 9000C. Rutherford backscattering spectrometry (RBS) has been used to measure the Ge composition and film thickness. The structural characterization was performed by using X-ray diffraction (XRD) and Raman spectrometry. XRD measurements confirmed the formation of Ge nanocrystals. Raman scattering spectra showed a peak of Ge-Ge vibrational mode around 299 cm−1, which was caused by quantum confinement of phonons in the Ge nanocrystals. Surface morphology of the samples was studied by atomic force microscopy (AFM). Variation of nanocrystal size with annealing temperature has been discussed. Advantages of microwave annealing are explained in detail.

Two diffusion pathways in quartz: A combined UV-laser and RBS study

The diffusive behavior of argon in quartz was investigated with three analytical depth profiling methods: Rutherford Backscattering Spectroscopy (RBS), 213 nm laser ablation, and 193 nm (Excimer) laser ablation on the same set of experimental samples. The integration of multiple depth profiling methods, each with different spatial resolution and sensitivity, allows for the cross-checking of methods where data ranges coincide. The use of multiple methods also allows for exploration of diffusive phenomena over multiple length-scales. Samples included both natural clear rock crystal quartz and synthetic citrine quartz. Laser analysis of clear quartz was compromised by poor coupling with the laser, whereas the citrine quartz was more easily analyzed (particularly with 193 nm laser). Diffusivity measured by both RBS and 193 nm laser ablation in the outermost 0.3 μm region of citrine quartz are self-consistent and in agreement with previously published RBS data on other quartz samples (including the clear quartz measured by RBS in this study). Apparent solubilities (extrapolated surface concentrations) for citrine quartz are in good agreement between RBS, 213 nm, and 193 nm laser analyses. Deeper penetration of argon measured up to 100 μm depth with the 213 nm laser reveal contributions of a second, faster diffusive pathway, effective in transporting much lower concentrations of argon into the crystal interiors of both clear and citrine quartz. By assuming such deep diffusion is dominated by fast pathways and approximating them as a network of planar features, the net diffusive uptake can be modeled and quantified with the Whipple–LeClaire equation, yielding δD b values of 1.32 × 10 −14 to 9.1 × 10 −17 cm 3/s. While solubility values from the measured profiles confirm suggestions that quartz has a large capacity for argon uptake (making it a potentially important sink for argon in the crust), the slow rate of lattice diffusion may limit its capability to take up argon in shorter lived geologic environments and in experiments. In such shorter-lived systems, bulk argon diffusive uptake will be dominated by the fast pathway and the quartz lattice (including natural isolated defects that may also be storing argon) may never reach its equilibrium capacity.

AFM, XPS and RBS studies of the growth process of CdS thin films on ITO/glass substrates deposited using an ammonia-free chemical process

This paper deals with a detailed study of the growth stages of CdS thin films on ITO/glass substrates by chemical bath deposition (CBD). The chemical and morphological characterization was done through X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), and atomic force microscopy (AFM) techniques. On the other hand, optical transmission and X-ray diffraction (XRD) measurements were performed in order to study the optical and structural properties of the films. The time, the chemistry, and morphology of the different stages that form the growth process by CBD were identified through these results. Furthermore, clear evidence was obtained of the formation of Cd(OH) 2 as the first chemical species adhered to the substrate surface which forms the first nucleation centers for a good CdS formation and growth. On the other hand, the ITO coating caused growth stages to occur earlier than in just glass substrates, with which we can obtain a determined thickness in a shorter deposition time. We were able to prove that CBD is a good technique for the manufacture of thin films of semiconductor materials, since the CdS film does not have any impurities. Completely formed films were transparent, uniform, with good adherence to the substrate, of a polycrystalline nature with a hexagonal structure. These results indicate that films obtained by CBD are good candidates to be applied in different optoelectronic devices.

Investigation of terbium scandate as an alternative gate dielectric in fully depleted transistors

Terbium scandate thin films were deposited by e-gun evaporation on (100) silicon substrates. Rutherford backscattering spectrometry and x-ray diffraction studies revealed homogeneous chemical compositions of the films. A dielectric constant of 26 and CV-curves with small hystereses were measured as well as low leakage current densities of <1 nA/cm2. Fully depleted n-type field-effect transistors on thin silicon-on-insulator substrates with terbium scandate gate dielectrics were fabricated with a gate-last process. The devices show inverse subthreshold slopes of 80 mV/dec and a carrier mobility for electrons of 225 cm2/V∙s was extracted.

Physico-chemical, structural and physical properties of hydrogenated silicon oxinitride films elaborated by pulsed radiofrequency discharge

Films prepared by radiofrequency pulsed plasma enhanced chemical vapor deposition from a mixture of silane (SiH 4) and nitrous oxide (N 2O) were studied. Variation of operating conditions (flow rate, deposition temperature ...) resulted in films with chemical compositions changing from hydrogenated silicon oxynitride (SiO x N y :H) to silicon oxide (SiO x :H). Infrared and Rutherford backscattering spectroscopy studies of the as-deposited films revealed different SiO x arrangements disturbed by Si–N bonds and H–Si ≡ Si (3 − x) O x clusters depending on the substrate temperature and the N 2O/SiH 4 ratio. For films obtained using low N 2O/SiH 4 rations and annealed at temperature higher than 1273 K, Raman spectroscopy and microscopy analyses revealed the presence of silicon nanocrystals embedded in a matrix containing Si, O, and N. Spectroscopic ellipsometry revealed the presence of silicon nanocrystals along with two other amorphous phases (SiO x N y and SiO 2) in annealed samples. The electrical characteristics of annealed films obtained from capacitance–voltage measurements indicated a stable charge trapping in ultra-thin SiO x N y layers. These preliminary results suggest that Si -nc containing silicon oxynitride layers can be potential candidates to be used in the floating gate fabrication of memory devices.