Rutherford Backscattering Spectrometry Spectra Research Articles

Interfacial reactions and surface analysis of W thin film on 6H-SiC

Tungsten (W) thin film was deposited on bulk single crystalline 6H-SiC substrate and annealed in vacuum at temperatures ranging from 700 to 1000°C for 1h. The resulting solid-state reactions, phase composition and surface morphology were investigated by Rutherford backscattering spectroscopy (RBS), grazing incidence X-ray diffraction (GIXRD) and scanning electron microscopy (SEM). XRD was used to identify the phases present and to confirm the RBS results. The RBS spectra were simulated using the RUMP software in order to obtain the deposited layer thickness, composition of reaction zone and detect phase formation at the interface. RBS results showed that interaction between W and SiC started at 850°C. The XRD analysis showed that WC and CW3 were the initial phases formed at 700 and 800°C. The concentration of the phases was however, too low to be detected by RBS analysis. At temperatures of 900 and 1000°C, W reacted with the SiC substrate and formed a mixed layer containing a silicide phase (WSi2) and a carbide phase (W2C). The SEM images of the as-deposited samples showed that the W thin film had a uniform surface with small grains. The W layer became heterogeneous during annealing at higher temperatures as the W granules agglomerated into island clusters at temperatures of 800°C and higher.

Ion beam analysis of Cu(In,Ga)Se2 thin film solar cells

The present work investigates the potential of ion beam analysis (IBA) techniques such as the Rutherford backscattering spectrometry (RBS) and particle induced X-ray emission (PIXE) using helium ions to provide quantitative in-depth elemental analysis of various types of Cu(In,Ga)Se2 thin films. These films with a thickness of about 2μm are used as absorber layers in photovoltaic devices with continuously increasing the performance of this technology. The preparation process generally aims to obtain an in-depth gradient of In and Ga concentrations that optimizes the optoelectronic and electrical properties of the solar cell. The measurements were performed at directly accessible single or double layered CIGS absorbers and at buried absorbers in completed thin film solar cells. The IBA data were analyzed simultaneously in order to derive best fitted profiles that match all experimental RBS and PIXE spectra. For some samples elemental profiles deduced form synchrotron based, reference free grazing incidence X-ray fluorescence analysis were compared with the IBA results and an overall good agreement was observed within quoted uncertainties.

Charging effects in the ion beam analysis of insulating polymers

We have studied the energy shift introduced by surface charging during the course of ion beam analysis of an insulating material (a Kapton thin film) using Rutherford Backscattering Spectrometry (RBS). The potential that develops was found to be proportional to both the incident ion energy and the sample thickness. This correlation suggests a conductance mechanism that is based on the ion beam induced carriers that are generated in the material. A simple relationship between the mobility of the induced carriers and the built-up surface potential has been derived. It provides a semi-quantitative explanation for the observed spectral offset. This relationship also provides important insight into the electrical characteristics of the insulating material being irradiated. In the specific case of Kapton, we observed a split of the high energy edge in the RBS spectra, which we suggest is most likely a reflection of the presence of both amorphous and crystalline forms of Kapton. Some contribution from partial discharge of the surface potential to the surrounding is also considered.

Calculation for optimization of the experimental conditions for RBS analysis at the HUS 5SDH-2 tandem accelerator

The dependences of the depth and mass resolutions of analysis using Rutherford Backscattering Spectrometry (RBS) on some experimental conditions (such as the beam energy, the target tilting angle, etc.) have been investigated. A computer program for simulating the RBS spectra and for calculating the depth and mass resolution under different experimental conditions was developed. The results of calculation were experimentally checked by using some reference samples. The good agreements between calculated and experimental values have been found. The optimum analysis conditions over a wide range of RBS applications based on our calculation can be chosen. This investigation was conducted by using the RBS system at HUS 5SDH-2 Tandem accelerator at the Hanoi University of Science.

Antibacterial effect of silver nanofilm modified stainless steel surface

Bacteria can attach to stainless steel surfaces, resulting in the colonization of the surface known as biofilms. The release of bacteria from biofilms can cause contamination of food such as dairy products in manufacturing plants. This study aimed to modify stainless steel surfaces with silver nanofilms and to examine the antibacterial effectiveness of the modified surface. Ion implantation was applied to produce silver nanofilms on stainless steel surfaces. 35 keV Ag ions were implanted with various fluences of 1 × 1015 to 1 × 1017 ions•cm-2 at room temperature. Representative atomic force microscopy characterizations of the modified stainless steel are presented. Rutherford backscattering spectrometry spectra revealed the implanted atoms were located in the near-surface region. Both unmodified and modified stainless steel coupons were then exposed to two types of bacteria, Pseudomonas fluorescens and Streptococcus thermophilus, to determine the effect of the surface modification on bacterial attachment and biofilm development. The silver modified coupon surface fluoresced red over most of the surface area implying that most bacteria on coupon surface were dead. This study indicates that the silver nanofilm fabricated by the ion implantation method is a promising way of reducing the attachment of bacteria and delay biofilm formation.

Self-consistent depth profiling and imaging of GaN-based transistors using ion microbeams

Using an ion microprobe, a comprehensive lateral and in-depth characterization of a single GaN-based high electron mobility transistor is carried out by means of Rutherford backscattering spectrometry (RBS) in combination with particle induced X-ray emission (PIXE). Elemental distribution was obtained for every individual section of the device (wafer, gate and source contact), identifying the basic constituents of the transistor (including the detection of the passivant layer) and checking its homogeneity. A self-consistent analysis of each individual regions of the transistor was carried out with a simultaneous fit of RBS and PIXE spectra with two different beam conditions. Following this approach, the quantification of the atomic content and the layer thicknesses was successfully achieved overcoming the mass-depth ambiguity of certain elements.

CVD Growth of GeSnSiC Alloys Using Disilane, Digermane, Tin Tetrachloride and Methylsilane

Ge-Sn-Si-C alloys offer a large range of strain engineering which gives the possibility to tailor the material properties for advanced photonic, electronic, photovoltaic and thermoelectric applications. The benefits of Ge-Sn-Si-C alloys are possibilities to obtain a direct-to-indirect transition (for Sn-based alloys) [1], high carrier mobility [2] and low cost process [3]. In this study, Ge1-x-y-zSnxSiyCz layers (0.01≤x≤ 0.24, 0≤y≤0.12 and 0≤z≤0.01) have successfully grown on Ge and Si by using RPCVD technique. It was demonstrated that the quality of epitaxial layers is dependent on the growth parameters, layer thickness and the quality of Ge virtual layer. It was found that a proper strain balance in the matrix during the epitaxy where the Si and Si-C is adjusted carefully compared to Sn flux improves the incorporation of Sn in Ge matrix. This is explained by the compensation of tensile strain induced by Si or Si-C with the compressive strain caused by Sn in order to obtain the minimum energy in Ge matrix. Fig. 1a and 1b show RBS spectra of two GeSnSi samples when the first one has a constant Si flux whereas the sample in Fig. 1b has a graded Si flux within GeSnSi layer. The Sn incorporation improved from 3% to 24% when Si flux was graded.Incorporation of P and B in GeSnSiC matrix has been studied and the effect of dopant concentrations on Sn content has been investigated. A low boron concentration in range of 1017 cm-3 could be incorporated in the epi-layers whereas P-doping in range of 1019 cm-3could be achieved. All Ge1-x-ySnxSiyCz layers were grown at 280-330 °C at 20 torr in a RPCVD reactor. The gas precursors were Si3H8, Ge2H6, 1% B2H6 in H2, 5% PH3 in H2, and SnCl4as Si, Ge, B, P and Sn sources, respectively. The strain in the epi-layers was measured by high-resolution x-ray reciprocal lattice maps (HRRLMs). Transmission electron microscopy (TEM) was applied to detect the defects in the epi-layers and to observe the interfacial quality. The Sn, Si and C content in the samples was measured by Rutherford backscattering spectrometry (RBS) and HRRLMs. The atomic dopant concentration in the epi-layers was measured by secondary ion mass spectrometry (SIMS). Four-probe measurements were done to determine the resistivity of the doped layers.The quality of carrier and reactant gases in terms of oxygen and water vapor was investigated by residual gas analyzer (RGA). The RGA instrument was connected to the exhaust gas output and was situated in 20 mm distance from the reactant gas chamber. A RGA spectrum reveals any absorption or desorption of molecules with accuracy of ppt range. The results showed that the level of oxygen during epitaxy was as low as 10 ppb and the contamination concetration was found as low as 1017 cm-3. This low oxygen level during epitxy is due to the high purity of trisilane, digermane and tetrachloride precursors as well as the hydrogen carrier gas. Acknowledgment The Swedish Research Council (VR) is greatly acknowledged for supporting this work.

Surface and interface roughness estimations by X‐ray reflectivity and RBS measurements

X‐ray reflectivity (XRR) is often used to estimate the interface roughness. In principle, XRR can measure both surface and interface roughness. However, the sensitivity to the interface roughness is rather poor compared with the surface roughness. In order to improve the accuracy in the interface roughness, a combination analysis of XRR with high‐resolution Rutherford backscattering spectroscopy was performed. The surface and interface roughness were determined so that both XRR and high‐resolution Rutherford backscattering spectroscopy spectra can be reproduced. We also found that the effective roughness measured by XRR may depend on the angle of incidence. This is because the roughness depends on the size of the probing area. Copyright © 2014 John Wiley & Sons, Ltd.

Influence of culture media on the physical and chemical properties of Ag–TiCN coatings

The aim of this study was to verify the possible physical and chemical changes that may occur on the surface of Ag–TiCN coatings after exposure to the culture media used in microbiological and cytotoxic assays, respectively tryptic soy broth (TSB) and Dulbecco's modified eagle's medium (DMEM). After sample immersion for 24 h in the media, analyses were performed by glow discharge optical emission spectroscopy discharge radiation (GDOES), Rutherford backscattering spectroscopy (RBS) and x-ray photoelectron spectroscopy (XPS). The results of GDOES profile, RBS and XPS spectra, of samples immersed in TSB, demonstrated the formation of a thin layer of carbon, oxygen and nitrogen that could be due to the presence of proteins in TSB. After 24 h of immersion in DMEM, the results showed the formation of a thin layer of calcium phosphates on the surface, since the coatings displayed a highly oxidized surface in which calcium and phosphorus were detected. All these results suggested that the formation of a layer on the coating surface prevented the release of silver ions in concentrations that allow antibacterial activity.

Degradation of ferroelectric and weak ferromagnetic properties of BiFeO3 films due to the diffusion of silicon atoms

Crystalline BiFeO3 (BFO) films each with a crystal structure of a distorted rhombohedral perovskite are characterized by X-ray diffraction (XRD) and high-resolution electron microscopy (HRTEM). The diffusion of silicon atoms from the substrate into the BiFeO3 film is detected by Rutherford backscattering spectrometry (RBS). The element analysis is performed by energy dispersive X-ray spectroscopy (EDS). Simulation results of RBS spectrum show a visualized distribution of silicon. X-ray photoelectron spectroscopy (XPS) indicates that a portion of silica is formed in the diffusion process of silicon atoms. Ferroelectric and weak ferromagnetic properties of the BFO films are degraded due to the diffusion of silicon atoms. The saturation magnetization decreases from 6.11 down to 0.75 emu/g, and the leakage current density increases from 3.8 × 10−4 up to 7.1 × 10−4 A/cm−2.

Kinetics of solid-state reactions between zirconium thin film and silicon carbide at elevated temperatures

Solid state reactions between a thin film (133nm) of Zr and bulk single crystalline 6H-SiC substrates have been studied at temperatures between 600°C and 850°C for durations of 30, 60 and 120min under high vacuum conditions. The deposited film and reaction zones were investigated by Rutherford backscattering spectrometry (RBS) and X-ray diffraction. The RBS spectra were simulated in order to obtain the deposited layer thickness, reaction zone compositions and reaction zone thickness. The as-deposited spectra fit well with those annealed at 600°C, thus showing there were no reactions taking place. At temperatures of 700°C and above, Zr reacted with the SiC substrate and formed a mixed layer of Zr carbide (ZrCx) and Zr silicides (ZrSi, Zr2Si and Zr5Si3). Annealing at 850°C for 240min revealed that all the deposited Zr had completely reacted. The interface reaction follows the parabolic growth law thereby indicating diffusion controlled reaction kinetics. The activation energy for the diffusion process obtained was 1.6eV in the relatively narrow temperature range 700–850°C.

Investigation of ion beam mixing threshold value in Mn/Si system using swift heavy ions

A metal/semiconductor system (a-Si/Mn/a-Si) was deposited on the silicon substrate using the electron beam evaporation method. These samples were irradiated using 80 MeV Ni and 100 MeV Ag ions at different fluences ranging from 1×1013 to 1×1014 ions/cm2 for the investigation of mixing threshold. Pristine and irradiated samples have been characterized using Rutherford backscattering spectroscopy (RBS) for depth profile analysis and atomic force microscopy (AFM) for surface roughness study. RBS spectra revels that there is a mixing at 100 MeV Ag ion irradiations which increases with fluence, whereas there is no mixing observed at 80 Ni MeV ion irradiations. We have also tried to investigate the mixing threshold value in this system. The surface roughness, as investigated from AFM, has not significantly changed upon irradiation indicating no contribution of roughness in interface mixing.

Characterization and testing of Pt/TiO2/SiC thin film layered structure for gas sensing

This paper presents the results of our investigations on the gas sensing performance of Pt/TiO2/SiC based field effect devices. The current–voltage characteristics of these Pt/TiO2/SiC sensors at 530°C showed a clear shift to lower voltages upon exposure to increasing hydrogen gas concentration. This indicates a reduction in the metal-oxide interface barrier height, arising from the flattening of the energy bands at the interface and can be attributed to the lowering of the Pt work function due to absorption of hydrogen. The effective change in barrier height Δφb for 1% hydrogen in air was found to be 125meV. The thermal stability of the interfaces in the Pt/TiO2/SiC devices was studied by Rutherford backscattering spectrometry (RBS). The RBS spectra of the sample in as deposited and annealed conditions were compared and analyzed. The Pt/TiO2 and TiO2/SiC layers showed a sharp interface with minimal inter-diffusion. The film composition found to be stable even after repeated testing by exposing to analyte gases. This was further confirmed by X-ray photoelectron spectroscopy analysis of the samples.

ERD measurement of depth profiles of H and Li in Pt-coated LiCoO2 thin films

By combining elastic recoil detection (ERD) analysis with Rutherford backscattering spectrometry (RBS) using 9.0-MeV oxygen-ion (O4+) probe beams from a tandem accelerator, we simultaneously investigated the distributions of lithium (Li), hydrogen (H), cobalt (Co), and platinum (Pt) in 20nm Pt/260nm LiCoO2 multi-layer thin films acting as the positive electrode in a solid-state Li+ ion battery and, deposited on Li1.4Ti2Si0.4P2.6O12–AlPO4 (LATP) substrates by using pulsed laser deposition. Measurement of the ERD and RBS spectra revealed the effects of Pt deposition on the hydrogen absorption characteristics of the LiCoO2 thin films, with segregation of Co to the surface as a catalyst. We speculate from the results that the presence of H in the LiCoO2 thin films has a marked influence on Li+ ion conduction in Li-battery systems.

In situ RBS measurements for the effect of swift heavy ion irradiation on metal–insulator interfaces

We have studied the effect of 200MeV Xe ion irradiation on Bi–Al2O3 and Au–Al2O3 interfaces by means of in situ Rutherford backscattering spectrometry (RBS). For the Bi–Al2O3 interface, we could observe a systematic change in RBS spectrum as a function of Xe ion fluence or the irradiation time. On the other hand, for Au–Al2O3 system, we could not observe any change in RBS spectrum. The experimental result confirmed our previous result that atomic mixing at Bi–Al2O3 interface surely occurs by the Xe ion irradiation. We analyzed the RBS spectra by the simulation software SIMNRA, and discussed the Bi–Al2O3 mixing quantitatively. From the irradiation time dependence of the mixing layer thickness, we estimated the effective diffusion constant for the atomic mixing at Bi–Al2O3 interface. Its value corresponds to the self-diffusion near the melting temperature of Al2O3. The result implies that Bi and Al2O3 are in molten forms during the ion irradiation, resulting in the atomic mixing at Bi–Al2O3 interface.

Synthesis Of Ag Nanoparticles On Polymer Surface: 150 KeV Ar Ion Irradiation Of Ag-PVC Bilayer

Thin metal films of Ag (~10 nm) deposited on spin coated PVC film on quartz substrate, were irradiated with 150 keV Ar ions at fluences varying from 5×10 15 to 5×10 16 ions/cm 2 and characterized with Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques. RBS spectra show sputtering of the Ag film. As a result of ion irradiation, isolated Ag nanoparticles are formed on the surface. The size and size distribution of Ag nanoparticles are found to be dependent on ion fluence. Contact angle measurements were carried out to study the hydrophilic nature of the surface at varying fluences. Results are explained in the framework of sputtering from the surface due to dense collision cascade resulting from Ar ion and Ag/PVC film interaction.

RBS depth profiling and optical characterization of multilayers of TiO2 (20 nm) and Ge (15 nm)

Rutherford Backscattering Spectrometry (RBS) has been employed for studying inter-layer diffusion and mixing of TiO2 and germanium in the multi-layers grown on the soda lime glass substrate. TiO2 layers were grown by electron-beam evaporation of titanium in an oxygen atmosphere and Ge layers were grown by resistive heating. UV–visible and Raman spectroscopy were carried out for optical characterization. RBS spectra were analyzed by SIMNRA which confirmed the successful formation of alternate layers of TiO2 and Ge with a thickness of 20 nm and 15 nm, respectively. Annealing caused interface mixing. The approximate stoichiometry of interfaces was of GeTiO2. The thickness of these layers increased with annealing temperature. Two to five top Ge layers also underwent oxidation to form GeO and GeO2, depending on annealing temperature. Nuclear Reaction Analysis (NRA) signal of oxygen from top layers was also recorded to confirm the pick-up of oxygen from the annealing atmosphere. An increase in the transmission efficiency with blue shift of the absorption edge was also observed with annealing temperature, as associated with the decrease in the effective thickness of Ge layers. Shift of Raman peaks confirmed the stoichiometric changes as a result of annealing.

130 MeV Au ion irradiation induced dewetting on In2Te3 thin film

In/Te bilayer thin films were prepared by sequential thermal evaporation and subsequently irradiated by 130MeV Au ions. The pristine and irradiated samples were characterized by X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques. RBS spectra reveal the sputtering of Te film and interface mixing, with increasing fluence. The surface morphology showed the beginning of dewetting of Te thin film and formation of the partially connected with the mixed zones at the fluence of 1×1013ions/cm2. At the higher fluence of 3×1013ions/cm2, dewetted structures were isolated at the surface. Above results are explained based on the formation of craters, sputtering and dewetting followed by inter-diffusion at the interface of molten zones due to thermal spike induced by Au ions.

Correlation between oxygen stoichiometry, structure, and opto-electrical properties in amorphous In2O3:H films

We have characterized amorphous In2O3:H (H : ∼4 at.%) transparent conducting films by Rutherford backscattering spectrometry (RBS), thermal desorption spectroscopy, spectroscopic ellipsometry, and Hall measurements. The amorphous In2O3:H films have been fabricated at room temperature by sputtering of an In2O3 ceramic target under Ar, O2, and H2O vapor with variation of a flow ratio r(O2) = O2/(O2+Ar). We observe (i) signals originating from Ar in RBS spectra for all the films and (ii) desorption of H2O and Ar gases during post thermal annealing of the films. Furthermore, O2 desorption together with H2O and Ar is observed for the films grown at r(O2) > 0.375%, whereas In desorption together with H2O and Ar is observed for the films grown at r(O2) < 0.375%. These results suggest that the films have void and/or multi-vacancy rich structures inside the amorphous network, and the variety of atoms, such as Ar, H2O, and weakly bonded O and In, is present in the void structures for the films grown at O2-rich and O2-poor conditions, respectively. Corresponding to the structural changes, optical and electrical properties also change at r(O2) = 0.375%. For the films grown at r(O2) < 0.375%, we observe a broad absorption in the visible wavelengths that cannot be explained by free carrier absorption. In this film, the carrier mobility reduces rapidly with increasing carrier density. Analysis of spectroscopic ellipsometry and Hall measurements reveals that a large decrease in mobility is due to a large increase in carrier effective mass, in addition to the effect of ionized impurity scattering. In this article, we discuss the optical and transport properties with the variation of oxygen stoichiometry and microscopic structures in the amorphous In2O3:H films.

Damage profiles and ion distribution in Pt-irradiated SiC

Single crystalline 6H-SiC samples were irradiated at 150K with 2MeV Pt ions. The local volume swelling was determined by electron energy loss spectroscopy (EELS), and a nearly sigmoidal dependence on irradiation dose is observed. The disorder profiles and ion distribution were determined by Rutherford backscattering spectrometry (RBS), transmission electron microscopy, and secondary ion mass spectrometry. Since the volume swelling reaches 12% over the damage region at high ion fluence, the effect of lattice expansion is considered and corrected for in the analysis of RBS spectra to obtain depth profiles. Projectile and damage profiles are estimated by SRIM (Stopping and Range of Ions in Matter). When compared with the measured profiles, the SRIM code predictions of ion distribution and the damage profiles are underestimated due to significant overestimation of the electronic stopping power for the slow heavy Pt ions. By utilizing the reciprocity method, which is based on the invariance of the inelastic energy loss in ion–solid collisions against interchange of projectile and target atom, a much lower electronic stopping power is deduced. A simple approach, based on reducing the density of SiC target in SRIM simulation, is proposed to compensate the overestimated SRIM electronic stopping power values, which results in improved agreement between predicted and measured damage profiles and ion ranges.