Depth Distribution Of Elements Research Articles

Decoupling Sources of Anthropogenic Influences on Sediments of the Visovac Lake (Krka National Park, Croatia) Using Multiparametric Approach.

Historical changes of sediment characteristics and levels of inorganic and organic contaminants were studied in dated sediment cores from the Visovac Lake, situated in the Krka National Park, Croatia, to identify the main sources of anthropogenic pressures on this highly protected system. Depth distributions of lithogenic elements showed a steady decrease of terrigenous inputs due to the reduction in agricultural activities in the area, which was particularly pronounced during the 1991-1995 war in Croatia. Vertical and longitudinal distributions of Cd and Zn indicated that they are predominately of anthropogenic origin. The historical profiles of these toxic metals coincide well with the recorded production of metal industry in the upper reach of the Krka River with a sharp decrease reflecting the interruption by the war and slow recovery afterwards. By contrast, the recovery of the tourist industry in Krka NP after the war was accompanied by increasing contamination by elements characteristic of boat and car traffic (Sn, Cu, Pb) as well as oil pollution. The contamination with polycyclic aromatic hydrocarbons and polychlorinated biphenyls was only moderate. Although levels of metallic and organic contamination can be considered relatively low, the observed shift from industrial to tourism-related sources indicated that touristic activities should also be regarded as a possible threat for this vulnerable karst aquatic ecosystem.

Influence of the oxidizing technique on the biocompatible and corrosion properties of Ti6Al4V in a physiological environment

This work aims to evaluate the corrosion and biocompatibility properties of oxide films generated on Ti6Al4V alloys using both traditional and novel methods. Oxide films were generated by anodization and plasma treatment to achieve a blue surface finish. The oxide films were then characterized and compared to a native film formed on the Ti6Al4V.Electrochemical tests, incorporating potentiodynamic tests and electrochemical impedance spectroscopy, were employed to define the electrochemical resistance of oxides in an environment simulating biological exposure. In vitro tests were conducted to study ion release and biocompatible properties over a 6-week period of exposure to a 0.9 wt% NaCl solution, at body temperature. Various spectroscopic techniques, including ToF-SIMS, XRD, and Raman analysis, were used to study the structure and chemistry of the oxide films. The sub-surface layer was analysed by microstructural investigation.The type of oxidation was found to have a key influence on the oxide composition, especially with respect to the depth distribution of the individual alloy elements through the oxide film. The oxidation process determines which of the alloying elements are released into the environment, as a result of the corrosion reactions.

Development of the passive film during passivation in passivating electrolytes containing sodium molybdate

The impact of sodium molybdate on passive films formed on lean duplex stainless steel (STS 329 FLD) was investigated. Elemental depth distribution was examined using glow discharge optical emission spectroscopy, while the analysis covered passive film capacitance, molybdenum's chemical state, and corrosion resistance. The addition of sodium molybdate to the passivation electrolyte resulted in a reduction of iron content in the iron-rich layer (from 48 % to 38 %), an increase in chromium content in the enhanced chromium layer (from 33 % to 42 %), and the presence of molybdenum on the film surface. Electrical impedance spectroscopy measurements indicated a significant increase in the capacitance of the passive film. Furthermore, molybdenum was identified as molybdate. Electrochemical anodic polarization curves revealed that the corrosion potential rose with the addition of sodium molybdate to the nitric acid electrolyte. This improvement in corrosion resistance was attributed to molybdate adsorption on the outermost part of the passive film, preventing chloride adsorption or penetration. Additionally, the corrosion current density decreased due to the presence of the chromium-rich layer.

Toward deeper ultraviolet detection: Atomic layer deposited amorphous AlGaOx thin film detector with its tunable optical properties and opto-electronic responses

Employing atomic layer deposition, AlGaOx films with varying Al concentrations (highest to 44% at.) were meticulously synthesized. Comprehensive characterization encompassing chemical composition, elemental depth distribution, structural clarity, and interface delineation unequivocally attested to the superior quality of the films. Optical properties were rigorously assessed using transmittance spectra and spectroscopic ellipsometry (SE), and optical constants across a broad spectral range (200–1000 nm) were determined through SE fitting. A consistent blue-shift in the absorption edge, observed in both the transmittance spectra and extinction coefficient, is attributed to the incorporation of aluminum. Detailed exploration via X-ray photoelectron spectroscopy fine scans of O 1s energy loss spectra and valence band analysis revealed that the evolution of the conduction band is instrumental in modulating the bandgap. To ascertain the viability for deep ultraviolet light detection, photodetectors based on AlGaOx were fabricated. Blue shifts in both photocurrent and response peak wavelength correlated with increasing Al content. In specific occasions, the AlGaOx-based detector has a responsibility of 0.05 A/W and 7×1013 detectivity of Jones. Remarkably, the detector demonstrates commendable on/off capability, characterized by fast rise and decay times of 0.26 s and 0.17 s, respectively. This study extensively examined the chemical, structural, and optical properties of amorphous AlGaOx films, alongside the optoelectronic capabilities of AlGaOx-based devices. Our research presented a viable strategy for enhanced deep ultraviolet detection, showcasing a successful implementation of amorphous bandgap engineering. This endeavor holds promise for future advancements in UV-detector development.

Ion Beam Analysis including ToF-ERDA of complex composition layers

When developing new materials for example, for high-temperature nuclear reactors with the potential of hydrogen production, that are characterized by radiation, high temperature and corrosion resistance, it is indispensable the knowledge of their detailed elemental composition and its possible variation with depth from surface. Several analytical methods based on different physical principles are used to determine the depth distribution of elements in the surface layers of materials. For the quantitative determination of elemental depth profile to a depth of several micrometres are applicable established Ion Beam Analysis (IBA) methods such as RBS, EBS, NRA and ERDA. Their advantage is that they are considered to be absolute and to a certain extent non-destructive. Each of these methods is advantageously used to analyse a certain range of elements, sometimes depending on the combination of other elements present. The recently commissioned Time of Flight Elastic Recoil Analysis (ToF-ERDA) measuring system at the Slovak University of Technology MTF in Trnava significantly enhanced the Ion Beam Laboratory capability of a comprehensive elemental analysis of thin films to the depth of hundreds of nanometres. Using the primary analysing 50 MeV Au beam, the depth profiles of all elements from W to H can be obtained within a single measurement. Analysis of complex samples using traditional IBA methods and high-energy ToF-ERDA is discussed and compared. The first measurements on the new ToF-ERDA installation are also presented.

Mechanism of Electrochemical Oxidation of Titanium Via Isotopic Labeling, Medium Energy Ion Scattering, Nuclear Reaction Profiling, in-Situ Rutherford Backscattering Spectrometry, and Electrochemical Impedance Spectroscopy

The few nanometres of titanium oxide present on titanium and Ti alloy surfaces are responsible for protecting the underlying metal from oxidation and enabling its use in many high-performance applications. The oxide provides a hard, uniform, and thermodynamically stable protective coating on an otherwise soft and very reactive metal. Because of its passivating oxide film, titanium has found uses in biomedical implants, aerospace engineering, corrosive industrial piping, and other areas where high strength and low weight are required.Our project is aimed at understanding the atomistic mechanisms of TiO2 formation and growth. We have taken several different approaches to investigate the details of this process. In one approach, the electrochemical oxidation mechanism of titanium at applied potentials between 0 and 10 V vs the saturated calomel reference electrode (SCE) was examined for ultra-thin Ti films sputtered onto Si(001) substrates and exposed in-situ to H2 18O, and then anodized in D2 16O. The effects of this isotopic labeling procedure were studied using medium energy ion scattering (MEIS) and nuclear reaction profiling (NRP). Both MEIS and NRP results are consistent in showing that the titanium oxide layer is composed of two distinct regions (Ti16O2/Ti18O2/Ti/Si) for the entire range of the formation voltages (0–10 V vs SCE). The oxygen component of the outermost region consists entirely of 16O, and the 18O region is always adjacent to the Ti metal. No Ti or 18O loss into the electrolyte solution during anodization was detected. The oxide thickened linearly as a function of potential in the 0–10 V range vs SCE, with experimental anodization ratio of 24.5±0.6 Å V−1. Mott–Schottky (MS) analyses showed positive slopes, indicating formation of an n-type TiO2 semiconductor, with O vacancies (or Ti interstitials) as major charge carriers in the 0–10 V range. Charge carrier densities, ND = (0.8-5.0)×1021 cm−3 were calculated from Mott–Schottky analysis and were well within the range of results reported in the literature. We observed a decrease in the charge carrier densities above ∼4 V vs SCE, that can be connected to defect annihilation or minor modification in the structure (electrostatic annealing) of the growing TiO2 film.In a second approach, we are using Rutherford backscattering spectrometry (RBS) for elemental depth profiling during oxide growth to determine oxidation rates and the role of the anodization potential on the Ti oxide layer structure and morphology. RBS is a powerful ion beam-based analytical tool used to determine thickness at the nanometer scale and elemental depth distribution, making it an excellent choice for studying the thin oxide on titanium. A difficulty with using RBS for such studies has been that RBS must function under ultra-high vacuum, and this has made it incompatible with performing aqueous electrochemistry; therefore, RBS had to be performed as an ex situ analysis, like MEIS and NRP. We are overcoming this limitation by using a specially designed in-situ cell with an ion-permeable silicon nitride window to provide a barrier between the ultra-high vacuum (UHV) required to perform RBS and the aqueous electrolyte solution required for anodization. In this cell, the thin silicon nitride window is coated with titanium and functions as the working electrode when exposed to the aqueous electrolyte solution. RBS measurements are taken as the titanium metal is anodized to titanium oxide. RBS is then performed during in-situ anodization, to obtain information about the growth mechanism of titanium oxide. Our initial in-situ RBS results show a significant increase in the oxidation rate of titanium compared to equivalent ex-situ measurements, and we also observe spontaneous TiO2 film growth without applying an anodic polarization. These effects are likely generated by strongly oxidizing water radiolysis products (e.g., H2O2 or ·OH) formed by the action of high-energy He+ ions interacting with the electrolyte solution.This paper discusses our experimental methods and presents an overview of the results and conclusions of this work.

Investigation of Oxide Thickness on Technical Aluminium Alloys—A Comparison of Characterization Methods

In this study the oxide layer of technical 6xxx aluminium surfaces, pickled as well as passivated, were comparatively investigated by means of transmission electron microscopy (TEM), Auger electron and X-ray photoelectron spectroscopy (AES, XPS), the latter in two different operating modes, standard and angle resolved mode. In addition, confocal microscopy and focused ion beam cutting were used for structural studies of the surfaces and for specimen preparation. The results illustrate in detail the strengths and weaknesses of each measurement technique. TEM offers a direct way to reliably quantify the thickness of the oxide layer, which is in the range of 5 nm, however, on a laterally restricted area of the surface. In comparison, for AES, the destructiveness of the electron beam did not allow to achieve comparable results for the thickness determination. XPS was proven to be the most reliable method to reproducibly quantify the average oxide thickness. By evaluating the angle resolved XPS data, additional information on the average depth distribution of the individual elements on the surface could be obtained. The findings obtained in this study were then successfully used for the investigation of the increase in the aluminium oxide thickness on technical samples during an aging test of 12 months under standard storage conditions.

External Beam IBA Measurements for Cultural Heritage

Ion beam analysis (IBA) methods refer to a set of analytical techniques based on the interactions of energetic ions, produced by a particle accelerator, with matter. The result of such interactions is the emission of characteristic radiation, X and gamma rays, and charged particles, which, upon detection, provide valuable information on the absolute concentration and depth distribution of the elements in the bombarded material. Moreover, IBA techniques can be performed while maintaining the object to be investigated at atmospheric pressure, without placing it in vacuum, in an analysis chamber, with the impinging ion beam extracted from the in-vacuum beamline of the accelerator, avoiding the need of invasive sampling and greatly easing the object positioning, thus allowing precious and big or large artefacts to be studied. This feature has opened the way for applications of IBA techniques for compositional analysis in cultural heritage studies, providing detailed and complete information about elemental compositions and depth distributions of analysed materials that are otherwise difficult or impossible for other analytical techniques. In this paper, the basic principles of the main IBA techniques applied to cultural heritage, namely, particle induced X-ray emission (PIXE), particle induced Gamma-ray emission (PIGE), and Rutherford or elastic backscattering spectrometry (RBS/EBS), will be recalled, and specific and practical details on how these techniques can be used for analysing cultural heritage objects with external beam set-ups will be provided.

Restoration of the original depth distribution from experimental SIMS profile using the depth resolution function in framework of RMR model

In this paper, the problem of depth profiling analysis of nanoscale heterostructures containing doped delta layers and quantum wells using the SIMS method is considered. Based on computer simulation data and previously obtained experimental data, we demonstrated that the RMR model most accurately and completely describes the redistribution of the analyzed element in ultrathin layers that occurs during ion sputtering. A comparative analysis of the surface roughness–ion mixing–recoil implantation (RMR) model with MRI (mixing-roughness-information depth) and UDS (up-and-down slope) models proposed by Hoffman and Dowsett, respectively, was performed. It was shown that the introduction into the MRI model of a parameter describing some layer of constant thickness, in which the components of the analyzed layer and matrix elements are uniformly mixed, is not quite justified. It is concluded that during depth profiling of a monoatomic layer, the center of mass of this layer shifts away from the surface, as predicted by the RMR model, rather than toward the surface, as predicted by the MRI model. It is found that preferential sputtering does not affect the experimental depth distribution of elements obtained by the SIMS method.

Profile distribution of trace elements under different land-use systems in North East India

ABSTRACT An investigation was carried out to study the depth-distribution of available trace elements and their relationship with soil physico-chemical properties in soils of Golaghat district, India. Soil samples were collected at 0-20 cm, 20-40 cm, 40-60 cm, 60-80 cm and 80-100 cm depth under five land use systems (LUS) viz. rice, vegetable, sugarcane, bamboo and tea. Particle size distribution data showed significant variation among the diverse LUS and soil depths. Soils were very strongly to medium acidic with a pH range of 4.7 to 5.7 and the highest was recorded at 80–100 cm depth under all the LUS. Soil organic carbon (SOC) content was higher in the surface layer and decreased with increasing soil depths. The highest (13.3 g kg−1) and lowest content of SOC (1.5 g kg−1) in soil were observed under tea and bamboo LUS. Exchangeable cations, cation exchange capacity and base saturation were higher in soils under rice LUS as compared to other LUS. Average DTPA extractable Fe, Mn, Zn and Cu content of the soils ranged from 10.3 to 80.3, 2.0 to 29.2, 0.1 to 0.8 and 0.1 to 1.8 mg kg−1 under diverse LUS.

Overview of methods for determining the depth distribution of elements in X-ray fluorescence analysis

X-ray fluorescence analysis is a frequently used analytical method in a number of areas for many decades, including the research of objects of cultural heritage. Especially in this area, the irreplaceable advantage is the fact that the measurement can be performed non-destructively and non-invasively on the examined object as a whole. It affects only a relatively thin layer at the surface of the object under investigation, nevertheless, this layer can have a complex structure (various coatings, gilding or other metallization, paint layers, etc.). Information about it can be a valuable contribution both to historical knowledge and to restoration work. During the development of the method, therefore, several procedures were elaborated to estimate the homogeneity or possible inhomogeneities of the investigated layer. In principle, the simplest one is to measure at different beam angles. However, this also changes the depth in the material into which the radiation penetrates. Without changing the measurement geometry, it is possible to use simultaneous detection of two different energy lines of the characteristic radiation of the investigated element (e.g., Kα and Kβ) and to evaluate the depth distribution on the basis of their ratio. Finally, the most sophisticated, but also the most informative, is the confocal arrangement of the spectrometer, where the focus, i.e. the intersection of the beams of incident and emitted radiation very narrowly collimated by the capillary optics, shifts to the depth of the measured material. This review paper summarizes the principles and possibilities of these methods, their advantages and limitations, and thus gives information for their use for specific needs. The use is illustrated by examples of specific measurements of art objects, realized in various laboratories, but especially in the laboratory of the authors of this paper.

Comparison of quantitative elemental depth distribution analyses of Ni and Ti in co-sputtered Ni-Ti alloy thin films using MCs+ and M+ secondary ions

Compositional uniformity in Ni-Ti thin alloy films, both at the surface and in the depth, significantly enhances their performance in various engineering applications. Quantitative depth distributions of Ni and Ti in magnetron co-sputtered Ni-Ti thin alloy films of various composition and thickness, were determined through an effective depth profiling technique. Secondary ion mass spectrometry (SIMS) was utilized to determine the qualitative elemental depth distribution of Ni and Ti in the films using MCs+-SIMS (Cs+ primary ion beam; MCs+ secondary ions, 'M' is the element of interest) and M+-SIMS (O2+ primary ion beam) approaches. The qualitative depth profiles were converted to quantitative depth profiles using the relative sensitivity factor values determined from the elemental concentrations obtained through energy dispersive x-ray spectroscopy analysis of one of the Ni-Ti thin film taken as reference. Thickness of the deposited films determined by x-ray reflectivity was used for depth scale calibration of SIMS raw profile. A comparison of the analytical capabilities of MCs+-SIMS and M+-SIMS approaches for determining the mean concentration and quantitative depth distribution of elements Ni and Ti in deposited Ni-Ti thin films has been presented.

Comparison and complementarity of QUASES-Tougaard and SESSA software

With the recent introduction of numerous commercial lab-scale high-energy X-ray photoemission spectrometers, new possibilities arise for photoemission spectra simulation. The most commonly available software are SESSA and QUASES-Tougaard. In this paper, we present and compare these software for the analysis of the inelastic background of X-ray photoelectron spectra. The QUASES-Tougaard software is a dedicated software for inelastic background analysis already well known for allowing to retrieve the depth distribution of complex stacks and deeply buried layers with a typical 5% accuracy. SESSA is a well-known software to facilitate quantitative interpretation of XPS spectra and to improve the accuracy of quantitative analysis but it is less commonly used for inelastic background analysis. This paper compares their capability to retrieve the depth distribution of elements and presents their main differences and complementarities. The two approaches are discussed using three well different systems from the microelectronic field with different levels of complexity such as the recurrence of an element in several layers or the combination of elements presenting very different cross-sections.

Implementation of Nanoscale Secondary‐Ion Mass Spectrometry Analyses: Application to Ni‐Based Superalloys

Secondary‐ion mass spectrometry (SIMS) is probably the most widely used chemical analysis technique in semiconductor science and in metallurgy because of its ultimate sensitivity to all elements and in particular to light elements providing semiquantitative information on the depth distribution of elements, for instance, doping elements (i.e., B, H), contaminants (i.e., C and O), chemical gradients, and segregation in thin films and at interfaces, etc. With the size shrinking of systems, high‐resolution 3D chemical imaging is becoming a prerequisite for the development of new materials at the nanoscale and for the deep understanding of the correlation between their properties and functionalities. Herein, the development of an innovative analytical SIMS implemented in a focused ion beam (FIB) (using Ga source)/scanning electron microscope (SEM) is reported. The equipment enables to give elemental chemical mapping at very high resolution (<30 nm) by precise optimization of the secondary‐ion optics and detection, while preserving excellent sensitivity, thanks to the integration of a gas injection system (GIS), which improves a positive (negative) ionization rate with oxygen (cesium) injection. The capability of the technique is demonstrated with nanoscale characterization of Ni‐based superalloys with broad applications in the manufacturing of engine parts and accessories for aircraft and aerospace equipment.

Are Perovskite Solar Cell Potential‐Induced Degradation Proof?

Potential‐induced degradation (PID) is a solar cell‐related degradation mechanism due to high potential difference in a photovoltaic (PV) module between the solar cells and its grounded frame. This type of degradation is well known for silicon PV; however, for perovskites it has not been thoroughly researched yet. Herein, the PID of perovskite solar cells is investigated for bias voltages of ±500 V, half of the currently used system voltage, and ±1000 V with regular I–V and electroluminescence measurements during the test. The devices show a high PID resistance under applied bias of ±500 V, far exceeding the recommended guidelines for silicon PV. However, for the bias voltage of –1000 V a rapid degradation is observed due to the ingress of sodium ions from the glass substrate as confirmed by the time‐of‐flight secondary ion mass spectrometry measurements of spatial and depth distribution of elements in solar cells. Positively biased devices show no degradation due to high voltage exposure. These results show promising signs that perovskite solar cells are PID proof for current PV system designs.

Determining the chronological sequence of inks deposited with different writing and printing tools using ion beam analysis.

Determining the sequence of inks in a questioned document is important in forensic science. Conventional and micro beam-based ion beam analysis using Rutherford backscattering spectrometry (RBS) and particle-induced X-ray emission were employed to study the depth distribution of chemical elements in plain paper and inks/toner deposited by different pens as well as inkjet and laser printers. Composition depth profiling with high lateral resolution was performed with focus on areas where two different coloring agents overlapped. We identify under which conditions the sequence of inks deposited can be reconstructed, analyzing the continuity of characteristic contributions to the obtained signals, with a focus on the depth-resolved RBS data. The order of deposition was correctly determined for combinations of two different laser printers and in certain cases for pens. Results indicate a potential for analysis, depending on the composition of staining agent, that is, in particular if heavy species are present in sufficiently high concentration. In such cases, also characters obscured or modified by an agent of different composition can be revealed. Changing the probing depth by modifying the beam energy could yield additional information.

Soil type modulates the response of C, N, P stocks and stoichiometry after native forest substitution by exotic plantations

Natural forests conversion to intensively managed forest plantation is an expanding land-use change that could profoundly impact C and nutrient terrestrial cycles. Here we assessed how different soil types respond to changes in the C, N, and P major biogeochemical pools by comparing paired natural broadleaf deciduous forest and pine plantation across five different soils with contrasting mineralogy. We quantified major biogeochemical stocks in all soil compartments to a depth up to 240 cm, including the forest floor. Our result showed that soils' C, N, and P stocks and stoichiometry do not respond equally to this land-use change. Deep soil biogeochemical pools (120–240 cm) contributed substantially to the total soil stock in most sites (up to 40% for C, 47% for P, and 52% for P). Elemental depth distribution was significantly modified because of forest substitution, and some sites displayed a significant stock reduction in deep soil compartments (>120 cm). Whole mineral soil C and N stocks were generally lower in the planted forest, while these stocks in litter layers were significantly different between soil and forest types (p < 0.001). C and N stocks in soils with low clay content or low activity clays were more significantly affected by forest substitution. On the other hand, soils with moderate to high clay content and dominant high activity clay were only mildly affected by this change. Phosphate and ammonium available pools were more affected in low activity and low clay content soil. P pools, and consequently C:P and N:P ratios in mineral soils, vary significantly between soil types. Our results corroborate that soils with contrasting properties respond differently to native forest substitution to intensively managed plantations and that the magnitude of this response seems to be controlled mostly by clay mineralogy.

Introductory guide to backgrounds in XPS spectra and their impact on determining peak intensities

Photoelectron and Auger peaks are central to most of the important uses of x-ray photoelectron spectroscopy (XPS), and thus, they receive the most attention in many types of analysis. Quantitative chemical analysis using XPS requires the assessment of the intensities of the photoemission peaks of the elements detected. Determination of peak intensities requires separation of the photoelectron peak signals from the background on which the peaks rest. For the determination of peak area intensities, the background is subtracted from overall signal intensity. The spectral background is also critical when peak fitting is used to determine intensities of overlapping peaks, and the model of background used in this process can impact the results. In addition to the impact on quantitative analysis, information about the depth distribution of elements in the near surface region can often be obtained by visual inspection of the background and quantified using appropriate modeling. This introductory guide provides some basic information about backgrounds in the XPS analysis, describes the types of background models that are commonly used, suggests some of their strengths and weaknesses, and provides examples of their use and misuse. Although the fundamental nature of some components of the background signals in XPS is not understood, indicating that none of the models in use are fully correct and the area is subject to active research, appropriate good practices have been established for most routine analysis. The guide describes good practices, identifies errors that frequently appear in the literature, and uses examples to demonstrate the impacts of background selections on determinations of peak intensities.

Memristor structure with the effect of switching resistance based on silicon nitride thin layers

The electrophysical properties and the resistive switching effect of the ITO/SiN x /Si memristor structure were studied. A silicon nitride film with a thickness of ~200 nm with an inhomogeneous element depth distribution was deposited by low-pressure chemical vapor deposition. Based on the Rutherford backscattering data, it was shown that the concentration of excess silicon atoms in the SiN x film increases from 9 to 44 % when approaching the Si substrate. The analysis of the current-voltage characteristics of ITO/SiN x /Si structures revealed that the conduction mechanism in the high-resistance state is determined by the nitride film properties and is described by the Poole-Frenkel model taking into account the hopping model of electron transport between traps. Switching to the low-resistance state is probably caused by the migration of indium or tin ions from the ITO contact to the SiN x layer. The conduction of the ITO/SiN x /Si structure in the low-resistance state is determined by both the mechanisms of charge-carrier injection from the contact and charge-carrier transport through the dielectric layer. Reverse polarity results in destructing the conductive channel and switching the structure to the high-resistance state. The photo-switching effect was found for the ITO/SiN x /Si structure, which opens up new possibilities of using memristors in silicon optoelectronic systems.

Investigations of elemental depth distribution and chemical compositions in the TiO2/SiO2/Si structures after ion irradiation

The influence of noble gases ion implantation on the depth distribution of elements in the TiO2/SiO2 bilayers on the Si substrates has been investigated using the Rutherford Backscattering Spectrometry (RBS). The structures were implanted by Ne+, Ar+, Kr+ or Xe+ ions with the energy of 100, 150, 200 or 250 keV. Using the SIMNRA code elemental composition and relative TiO2 and SiO2 as well as TiO2/SiO2 transition layers thicknesses were calculated for different ion species and energies. It was found that the thickness of the transition layers increased after the ion implantation. The effect is evident for Kr+ and Xe+ ions and its magnitude grows with the implanted ion energy. The chemical composition of the near-surface TiO2 layers was determined using the X-ray photoelectron spectroscopy (XPS) method. It was observed that the TiO and Ti2O3 concentrations increase while those of TiO2 and Ti decrease as a function of the implanted ions energy due to atomic displacement during the irradiation process. This effect could be considered as one of the reasons that affects the mixing process at TiO2/SiO2 interfaces induced by ion beam.