The interdiffusion and solid-state reaction of low-energy copper ions implanted in silicon

At room temperature, single-crystal silicon was implanted with Cu⁺ ions at an energy of 80 keV using two doses of 5 × 10¹⁵ and 1 × 10¹⁷ Cu⁺ cm⁻². The samples were heat treated by conventional thermal annealing at different temperatures: 200 °C, 230 °C, 350 °C, 450 °C and 500 °C. The interdiffusion and solid-state reactions between the as-implanted samples and the as-annealed samples were investigated by means of Rutherford backscattering spectrometry (RBS) and X-ray diffraction (XRD). After annealing at 230 °C, the XRD results of the samples (subject to two different doses) showed formation of Cu₃Si. According to RBS, the interdiffusion between Cu and Si atoms after annealing was very insignificant. The reason may be that the formation of Cu₃Si after annealing at 230 °C suppressed further interdiffusion between Si and Cu atoms.     

Fe-implanted SiC as a potential DMS: X-ray diffraction and rutherford backscattering and channelling study

Single crystalline (0 0 0 1)-oriented 6H-SiC samples were implanted at 380 °C with low-energy Fe ions (in the 100 keV range) with the aim of synthesizing so-called diluted magnetic semiconductors. X-ray diffraction and Rutherford backscattering spectrometry and channeling are used to study the microstructural changes in these Fe-implanted SiC crystals submitted to furnace annealing and laser processing, both treatments being performed in order to eliminate the implantation-induced defects.     

Structural and gasochromic properties of epitaxial WO3 films prepared by pulsed laser deposition

The structural and gasochromic properties of epitaxial tungsten trioxide (WO₃) thin films, prepared by ArF excimer pulsed laser deposition under the controlled oxygen atmosphere, have been investigated. The WO₃ films were grown on the α-Al₂O₃ substrates, as the oxygen pressure ranged from 0.57 to 1.20 Pa and the substrate temperature ranged from 432 to 538 °C. The deposited films were characterized by Rutherford backscattering spectroscopy (RBS)/channeling, X-ray diffraction, X-ray pole figures and Raman spectroscopy. RBS and XRD results demonstrated that monoclinic WO₃ (0 0 1) films were successfully grown on the α-Al₂O₃ substrates. The crystal quality was improved by increasing both the oxygen pressure and the substrate temperature. Gasochromic coloration in the WO₃ films by exposure to diluted hydrogen gas was found to correlate with the crystal quality of the films. The gasochromic coloration was suppressed by the epitaxial growth of the films.     

MeV-ion beam analysis of the interface between filtered cathodic arc-deposited a-carbon and single crystalline silicon

Amorphous carbon (a-C) films were deposited on Si(1 0 0) wafers by a filtered cathodic vacuum arc (FCVA) plasma source. A negative electrical bias was applied to the silicon substrate in order to control the incident energy of carbon ions. Effects of the electrical bias on the a-C/Si interface characteristics were investigated by using standard Rutherford backscattering spectrometry (RBS) in the channeling mode with 2.1-MeV He²⁺ ions. The shape of the Si surface peaks of the RBS/channeling spectra reflects the degree of interface disorder due to atomic displacement from the bulk position of the Si crystal. Details of the analysis method developed are described. It was found that the width of the a-C/Si interface increases linearly with the substrate bias voltage but not the thickness of the a-C film.     

Spectral analysis method for deriving RBS-like carbon spectra from the C(α,α)C resonant reaction

This article presents a spectral analysis method that detects C using the high-sensitivity of the 4.26 MeV resonance of the ¹²C(α,α)¹²C nuclear reaction while avoiding issues arising from the peaky and asymmetric resonance shape, which complicates depth-sensitive C analysis. By averaging nuclear reaction spectra taken with a set of conveniently chosen He beam energies, we obtain C spectra with amplified intensity, but shape similar to Rutherford backscattering spectrometry (RBS) spectra. The latter fact allows intuitive reading of underlying C depth profiles without employing spectrum simulation software. The method was first applied to simulated samples whose nuclear reaction spectra were generated by SIMNRA, which allowed checking for method accuracy by comparison to corresponding simulated RBS spectra. As real examples of the method application, it was applied to detect depth-sensitive C signals from SiC substrates covered by SiO₂ layers and from 50 nm hafnium-based films deposited on Si by metal-organic chemical vapor deposition.     

Oxidation resistance of Y-implanted steel using accelerator based techniques

The thermal oxidation behavior in air of Y-implanted (fluence 2 × 10¹⁷ ions/cm²) and non-implanted stainless steel AISI-321 samples was investigated using the ¹⁶O(d,p)¹⁷O nuclear reaction and Rutherford backscattering spectrometry (RBS). The oxidation temperature was 650 and 900 °C and the duration of the thermal treatment 48 hours. The influence of the implantation energy (40, 55 and 80 keV) on the oxidation behavior of stainless steel was also studied. An improvement of the oxidation resistance of the Y-implanted samples with increasing implantation energy was observed. Additional secondary ion mass spectroscopy (SIMS) measurements of the samples implanted by 40 keV Y-ions also indicated a slight chromium depletion of their near-surface layers. Mechanisms attempting to explain the experimental results are proposed.     

Strain-free Al0.08In0.018Ga0.902N/GaN heterostructure: Combined Rutherford backscattering/channeling and high resolution X-ray diffraction

A 160 nm Al_0.08In_0.018Ga_0.902N layer was grown by metal-organic chemical vapour deposition (MOCVD) on sapphire (0 0 0 1) with thick (>1 μm) GaN intermediate layer. The chemical compositions can be determined by Rutherford backscattering (RBS). The perpendicular and parallel strain of Al_0.08In_0.018Ga_0.902N layer was derived to be zero by using a combination of high resolution X-ray diffraction (HRXRD) and RBS/channeling. The conclusion is further evidenced by transmission electron microscopy (TEM).     

FTIR and RBS study of ion-beam synthesized buried silicon oxide layers

Single crystal silicon samples were implanted at 140 keV by oxygen (¹⁶O⁺) ion beam to fluence levels of 1.0 × 10¹⁷, 2.5 × 10¹⁷ and 5.0 × 10¹⁷ cm⁻² to synthesize buried silicon oxide insulating layers by SIMOX (separation by implanted oxygen) process at room temperature and at high temperature (325 °C). The structure and composition of the ion-beam synthesized buried silicon oxide layers were investigated by Fourier transform infrared (FTIR) and Rutherford backscattering spectroscopy (RBS) techniques. The FTIR spectra of implanted samples reveal absorption in the wavenumber range 1250-750 cm⁻¹ corresponding to the stretching vibration of Si-O bonds indicating the formation of silicon oxide. The integrated absorption band intensity is found to increase with increase in the ion fluence. The absorption peak was rather board for 325 °C implanted sample. The FTIR studies show that the structures of ion-beam synthesized buried oxide layers are strongly dependent on total ion fluence. The RBS measurements show that the thickness of the buried oxide layer increases with increase in the oxygen fluence. However, the thickness of the top silicon layer was found to decrease with increase in the ion fluence. The total oxygen fluence estimated from the RBS data is found to be in good agreement with the implanted oxygen fluence. The high temperature implantation leads to increase in the concentration of the oxide formation compared to room temperature implantation.     

Modeling of ion beam induced damage in Si during channeling Rutherford backscattering spectrometry analysis

We have modeled damage creation by an analyzing beam during channeling Rutherford backscattering spectrometry (RBS) analysis. Based on classic scattering theory and the assumption that only a dechanneled ion beam can cause displacements, a chi-square approach is used to fit the modeled spectra with experimental profiles, to extract the dechanneling cross section and the displacement creation efficiency. The study has shown that, for a 2.0 MeV He beam channeled along a Si(1 0 0) axis, the efficiency of defect creation by dechanneled beams is about 8% of the value predicted from the Kichin-Pease model. This suggests a significant dynamic annealing of point defects. The modeling procedure in this work can be used to predict the displacement creation during channeling RBS analysis.     

Structural study of the oxidation process and stability of NbOxNy coatings

In the present work, we study the oxidation behaviour of NbON multilayer films. The films were deposited by DC magnetron sputtering with a reactive gas pulsing process. The nitrogen flow was kept constant and the oxygen flow was pulsed. Pulse durations of 10 s produced multilayered coatings with a period of λ = 10 nm. Three different films with increasing duty cycles have been deposited.Rutherford backscattering spectroscopy (RBS) was used to study the chemical composition variations at different annealing temperatures (as-deposited, 400 °C, 500 °C and 600 °C) combined with X-ray diffraction (XRD) to identify the crystalline phases formed. At 400 °C, for all films a very thin layer starts to form at the surface with enhanced O concentration. The composition of the deeper part of the samples remains unchanged. At 500 °C, the oxide scale grows, encompassing about half the film thickness. At 600 °C, the process is finished and a single layer is formed with reduced Nb and increased O concentration. Fourier-transformation infrared spectroscopy (FTIR) results confirmed the increase of this surface oxidation, while XRD revealed that crystallization of Nb₂O₅ occurs at 600 °C.     

RBS study of Ti/ZnO interface

We have studied the interface stability of the Ti(overlayer)/ZnO(substrate) system. Ti thin film was grown on the Zn face of single crystal ZnO(0 0 0 1) substrate by the vacuum deposition technique. The Ti film thickness was typically 16 nm. Then the samples were annealed in air at 300 and 400 °C for 15 min, respectively. The deposition and annealing effects on the interface structure were investigated with Rutherford backscattering and channeling spectroscopy using 2 MeV He⁺ ion beam. After Ti deposition the minimum yield from the ZnO substrate increased from 2% to 7%. This suggests severe damage caused by deposition, i.e. the interface reaction between Ti and ZnO (even at room temperature). A significant amount of Zn (approximately 6.4 × 10¹⁶ atoms/cm²) moved onto the surface after post-annealing at 400 °C. Since Ti has a stronger tendency to react with O than Zn, it is expected that Ti reacts with substrate oxygen leaving behind free Zn atoms, which can easily migrate onto the surface. We discuss how the Ti/ZnO interface reaction in detail, and seek to find another good metallic contact for ZnO devices, which are attracting much attention recently for practical applications as well as scientific aspects.     

The use of HI-ERDA/RBS and NRA/RBS to depth profile N in GaAs1−xNx thin films

N profiles of several GaAs_1−xN_x epitaxial layers with different N mole fractions in the range 0 < x < 0.14 were obtained by using (1) heavy-ion elastic recoil detection analysis (HI-ERDA) along with Rutherford backscattering spectrometry (RBS) using a 35 MeV Si⁶⁺ beam, and (2) nuclear reaction analysis (NRA) with the ¹⁴N(α, p)¹⁷O reaction, also with RBS, using a 3.7 MeV ⁴He⁺ beam. The results from the two techniques are compared and the advantages, disadvantages and capabilities are discussed.     

Ion beam studies on reactive DC sputtered manganese doped indium tin oxide thin films

Indium based transparent conducting oxides doped with magnetic elements have been studied intensively in recent years with a view to develop novel ferromagnetic semiconductors for spin-based electronics. In the present work, we have grown manganese doped indium tin oxide (Mn:ITO) thin films, onto Si and Si/SiO₂ substrates by DC reactive sputtering of a composite target containing indium-tin alloy and manganese, in a gas mixture of oxygen and argon. Glancing angle X-ray diffraction (GXRD) studies reveal the polycrystalline nature of the films. Magnetic measurements carried out using vibrating sample magnetometer (VSM) suggest that the films are ferromagnetic at room temperature, with a saturation magnetization of ∼22.8 emu/cm³. The atomic percentages of In, Sn, Mn and O, as estimated using Rutherford backscattering spectrometry (RBS) are 37.0, 4.0, 1.6 and 57.4, respectively. RBS measurements reveal that the interface of the films with Si substrate has a ∼30 nm thick intermediate layer. This layer consists of oxygen, silicon, indium, tin and manganese, in the ratio 1:0.56:0.21:0.07:0.03, indicative of diffusion of elements across the interface. The films on Si/SiO₂, on the other hand, have a sharp interface.     

Effects of composition and structure on hydrogen incorporation in tungsten oxide films deposited by sputtering

The effects of composition and structure on hydrogen incorporation in tungsten oxide films were investigated. Films were deposited on carbon and SiO₂ substrates using a reactive sputtering by varying the substrate temperature from 30 to 600 °C in argon and oxygen mixture. The films were characterized using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), elastic recoil detection analysis (ERDA) and Raman scattering. XRD patterns showed amorphous structure in the films deposited below 400 °C and (0 1 0) oriented monoclinic WO₃ in the films deposited beyond 400 °C. The results of RBS and ERDA indicated that hydrogen concentration in the amorphous films increased from 0.1 to 0.7 H/W with changing the composition from WO_0.25 to WO₃. The hydrogen concentration in WO₃ films decreased to 0.4 H/W with increasing the substrate temperature during deposition. The Raman spectra of the WO₃ films revealed that decreasing of W⁶⁺O terminals was related to decreasing of the hydrogen concentration. It was considered that the incorporated hydrogen in tungsten oxide films was bonded at the end of W⁶⁺O terminals.     

Ion beam characterization of rf-sputter deposited AlN films on Si(1 1 1)

Aluminum nitride (AlN) thin films have been deposited on Si(1 1 1) substrates by using reactive-rf-magnetron-sputtering at 250 °C. The crystalline quality and orientation of the films have been studied by X-ray diffraction (XRD). We have observed that the films grow with c- or a-axis orientation. The composition, film thickness, impurities and stress are considered to be factors affecting the orientation and have been analyzed by Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA) and XRD. Their effects on the film growth will be discussed. Surface morphology of the films will be also presented.     

Characterisation of annealed Fe/Ag bilayers by RBS and XRD

Recently Fe/Ag thin films have been intensively investigated due to their special magnetic properties. To study the stability of the Fe–Ag interfaces very long time experiments are necessary at room temperature. To enhance the processes which take place at interfaces, high temperature annealing can be used. A detailed annealing experiment was carried out on Si-covered Fe/Ag (Ag grown on Fe) and Ag/Fe (Fe grown on Ag) polycrystalline bilayers, which were deposited on Si(1 1 1) substrates by MBE method. Heat treatments of various duration and temperature were applied in UHV conditions. Rutherford backscattering spectrometry and X-ray diffractometry were used to determine the effects of the heat treatments. In case of Fe/Ag samples, formation of iron–silicide phases was observed between the Fe layer and Si substrate, and the silver and the silicon capping layer were also completely mixed with each other. In case of the Ag/Fe samples the silver moved to the sample surface through the iron layers, while iron shifted to the substrate and mixed with silicon.     

Study of new sheep bone and Zn/Ca ratio around TiAlV screw: PIXE-RBS analysis

This study reports on in vivo particle induced X-ray emission (PIXE) measurements combined with Rutherford backscattering spectroscopy (RBS) analyses of new remodeled sheep bone formed around TiAlV screws. The implants (screws) were anodized by a modified TiMax™ process. The interface between the implant and the bone was carefully investigated. [Zn]/[Ca] in-depth composition profiles as well as Ca, Fe elemental maps were recorded. The thickness of new bone formed around the screw reached 300-400 μm. Osteon and Osteoid phases were identified in the new bone. A higher [Zn]/[Ca] ratio was observed in the new bone as compared to the mature bone. Blood vessels were observed in the bone in close contact with the screw.This study shows the potential of ion beam analysis for biological and biomedical characterization.     

A systematic study on analysis-induced radiation damage in silicon during channeling Rutherford backscattering spectrometry analysis

Channeling Rutherford backscattering spectrometry (RBS) is an essential analysis technique in materials science. However, the accuracy of RBS can be significantly affected by disorders in materials induced by the analyzing ion beam even under channeling mode. We have studied RBS analysis-induced radiation damage in silicon. A 140-keV H⁺ ion beam was incident along 〈1 0 0〉 Si axis at room temperature to a fluence ranging from 1.6 × 10¹⁶ cm⁻² to 7.0 × 10¹⁶ cm⁻². The evolution of the aligned yields versus fluences has been examined and found to agree well with a model proposed by us.     

Artificial neural networks for instantaneous analysis of real-time Rutherford backscattering spectra

This paper reports on the advantage of using artificial neural networks (ANNs) to analyze large sets of real-time Rutherford backscattering spectrometry (RBS) data. Real-time RBS, i.e. collecting RBS spectra at periodic time intervals during a thermal treatment, probes the full response of a thin film to the annealing in situ. Although very valuable insights can be gained by this technique, the time-consuming analysis of the vast amount of RBS spectra acquired during real-time RBS measurements has so far prevented the widespread use of real-time RBS. Setting up an ANN is quite an intensive process as well, but once trained, these ANNs can handle the analysis of large data sets practically instantaneously. As such, the beneficial combination of real-time RBS and ANN analysis forms a perfect synergy. In this test case, a network was trained and applied to analyze the Ni silicide growth during annealing of a thin 80 nm Ni film on Si(1 0 0). The ANN performance was validated by comparing the ANN results with the conventional analysis performed on the same data set.     

Temperature dependence of lattice disorder in Ar-irradiated (1 0 0), (1 1 0) and (1 1 1) MgO single crystals

To better appreciate dynamic annealing processes in ion irradiated MgO single crystals of three low-index crystallographic orientations, lattice damage variation with irradiation temperature was investigated. Irradiations were performed with 100 keV Ar ions to a fluence of 1 × 10¹⁵ Ar/cm² in a temperature interval from −150 to 1100 °C. Rutherford backscattering spectroscopy combined with ion channeling was used to analyze lattice damage. Damage recovery with increasing irradiation temperature proceeded via two characteristic stages separated by 200 °C. Strong radiation damage anisotropy was observed at temperatures below 200 °C, with (1 1 0) MgO being the most radiation damage tolerant. Above 200 °C damage recovery was isotropic and almost complete recovery was reached at 1100 °C. We attributed this orientation dependence to a variation of dynamic annealing mechanisms with irradiation temperature.