Quantitative Depth Profiling Research Articles

Spatially Resolved Large Magnetization in Ultrathin BiFeO3.

Here, a quantitative magnetic depth profile across the planar interfaces in BiFeO3 /La0.7 Sr0.3 MnO3 (BFO/LSMO) superlattices using polarized neutron reflectometry is obtained. An enhanced magnetization of 1.83 ± 0.16 μB /Fe in BFO layers is observed when they are interleaved between two manganite layers. The enhanced magnetic order in BFO persists up to 200 K. The depth dependence of magnetic moments in BFO/LSMO superlattices as a function of the BFO layer thickness is also explored. The results show the enhanced net magnetic moment in BFO from the LSMO/BFO interface extends 3-4 unit cells into BFO. The interior part of a thicker BFO layer has a much smaller magnetization, suggesting it still keeps the small canted AFM state. The results exclude charge transfer, intermixing, epitaxial strain, and octahedral rotations/tilts as dominating mechanisms for the large net magnetization in BFO. An explanation-one suggested by others previously and consistent with the observations-attributes the temperature dependence of the net magnetization of BFO to strong orbital hybridization between Fe and Mn across the interfaces. Such orbital reconstruction would establish an upper temperature limit for magnetic ordering of BFO.

Selective analysis of the elemental composition of InGaAs/GaAs nanoclusters by secondary ion mass spectrometry

New possibilities of the method of secondary ion mass spectrometry (SIMS) in application to quantitative analysis of the atomic composition of InGaAs nanoclusters in GaAs matrix are considered. Using In x Ga1–x As test structures, nonlinear calibration dependences of the yield of secondary In2As and InAs ions on the concentration of indium have been determined, which do not involve normalization to the matrix elements (Ga or As) and make possible selective analysis of the composition of nanoclusters. Using these relations, quantitative depth profiles of indium concentration were measured and statistical characteristics of the arrays of nanoclusters in InGaAs/GaAs heterostructures were determined.

Oxy-nitrides characterization with a new ERD-TOF system

A new time-of-flight (TOF) camera was installed on Elastic Recoil Detection (ERD) measurement setup on the Tandem Accelerator at Université de Montréal. The camera consists of two timing detectors, developed and built by the Jyvaskyla group, that use a thin carbon foil and microchannel plates (MCP) to produce the start and stop signals. The position of the first detector is fixed at 18cm from the target, while the position of the second detector can be varied between 50 and 90cm from the first detector. This allows to increase time resolution by increasing the distance between the time-of-flight detectors or to increase solid angle by decreasing the distance. Moving the detector also helps determining the parameters such as the effective distance between detector foils and the delay time.Compared to the original system, which had only one timing detector and relied on a surface barrier energy detector to measure both the energy and the stop signal, in the new system the energy is now obtained from the timing signal with much better resolution, reaching ∼4nm near the surface. There is also no more need to keep track of the surface barrier detector calibration for each element, including the pulse height defect.We show examples of quantitative depth profiles of oxy-nitride layers that has been characterized with this new system. It allows quantitative depth profiling of targets that would be difficult to analyze with other techniques, especially when light elements such as hydrogen, carbon, or nitrogen are mixed in various proportions in a heavy element matrix.

Water Plume Temperature Measurements by an Unmanned Aerial System (UAS)

We report on the development and testing of a proof of principle water temperature measurement system deployed on an unmanned aerial system (UAS), for field measurements of thermal discharges into water. The primary elements of the system include a quad-copter UAS to which has been integrated, for the first time, both a thermal imaging infrared (IR) camera and an immersible probe that can be dipped below the water surface to obtain vertical water temperature profiles. The IR camera is used to take images of the overall water surface to geo-locate the plume, while the immersible probe provides quantitative temperature depth profiles at specific locations. The full system has been tested including the navigation of the UAS, its ability to safely carry the sensor payload, and the performance of both the IR camera and the temperature probe. Finally, the UAS sensor system was successfully deployed in a pilot field study at a coal burning power plant, and obtained images and temperature profiles of the thermal effluent.

Depth profile by Total IBA in perovskite active layers for solar cells

In recent years the record efficiency of perovskite solar cells (PSCs) has been updated exceeding now 20%. However, it is difficult to make PSCs consistently. Definite correlation has been established between the PSC performance and the perovskite film quality which involves mainly morphology, crystallinity and composition. The manufacturing development of these devices is dependent on the characterisation methodologies, on the availability of suitable and reliable analytical techniques to assess the materials composition and quality and on the relationship of these results with the cell performance. Ion beam analytical (IBA) techniques jointly with a micro-ion beam are powerful tools for materials characterisation and can provide a valuable input for the knowledge of perovskite films.Perovskite films based on CH3NH3PbI3 were prepared (from CH3NH3I and PbI2 precursors) in a planar architecture and in a mesoporous TiO2 scaffold.Proton and helium micro-beams at different energies were used in the analysis of PSC active layers, previously characterised by SEM-FEG (Scanning Electron Microscopy with a field emission gun) and XRD (X-ray diffraction). Self-consistent fit of all the obtained PIXE (Particle Induced X-ray Emission) and RBS (Rutherford Backscattering Spectrometry) spectra through Total IBA approach provided depth profiling of perovskite, its precursors and TiO2 and assess their distribution in the films. PbI2 presence and location on the active layer may hinder the charge transport and highly affect the cell performance. IBA techniques allowed to identify regions of non-uniform surface coverage and homogeneous areas and it was possible to establish the undesired presence of PbI2 and its quantitative depth profile in the planar architecture film. In the mesostructured perovskite film it was verified a non-homogeneous distribution with a decreasing of perovskite concentration down to the thin blocking layer. The good agreement between the best fits obtained in a Total IBA approach and the experimental data granted reliability to depth profile results for the studied perovskite films.

TOF‐SIMS matrix effects in mixed organic layers in Ar cluster ion depth profiles

Matrix effects are crucial for analyses using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) in terms of quantitative analysis, depth profiling and imaging. It is often difficult to predict how co‐existing materials will influence each other before such analysis. However, matrix effects need to be curtailed in order to assume the appropriate amount of a target material in a sample. First, matrix effects on different types of organic mixed samples, including a sample composed of Irganox 1010 and Irganox 1098 (MMK sample) and another composed of Irganox 1010 and Fmoc‐pentafluoro‐L‐phenylalanine (MMF sample), were observed utilizing ToF‐SIMS and the dependence of the secondary ion polarity of the matrix effects on the same sample was evaluated. Next, the correction method for the ToF‐SIMS matrix effects proposed by Shard et al. was applied to a comparison of the positive secondary ion results to the negative ones. The matrix effects on the positive ion data in both samples were different from those on the negative ion data. The matrix effect correction method worked effectively on both the negative and positive depth profiles. Copyright © 2017 John Wiley & Sons, Ltd.

3D Auger quantitative depth profiling of individual nanoscaled III–V heterostructures

The nanoscale chemical characterization of III–V heterostructures is performed using Auger depth profiling below decananometric spatial resolution. This technique is successfully applied to quantify the elemental composition of planar and patterned III–V heterostructures containing InGaAs quantum wells. Reliable indium quantification is achieved on planar structures for thicknesses down to 9 nm. Quantitative 3D compositional depth profiles are obtained on patterned structures, for trench widths down to 200 nm. The elemental distributions obtained in averaged and pointed mode are compared. For this last case, we show that Zalar rotation during sputtering is crucial for a reliable indium quantification. Results are confirmed by comparisons with secondary ion mass spectrometry, photoluminescence spectroscopy, transmission electron microscopy and electron dispersive X-ray spectroscopy. The Auger intrinsic spatial resolution is quantitatively measured using an original methodology based on the comparison with high angle annular dark field scanning transmission electron microscopy measurements at the nanometric scale.

Quantitative SIMS depth profiling of Al in AlGaN/AlN/GaN HEMT structures with nanometer-thin layers

The possibilities of quantitative secondary ion mass spectrometry (SIMS) depth profiling of Al in AlxGa1 − xN/AlN/GaN transistor heterostructures are shown. Using a series of test structures for a TOF.SIMS-5 time-of-flight mass spectrometer, we obtained a refined linear calibration dependence of the secondary-ion yield on the composition ×, namely, Y(CsAl+)/Y(CsGa+) = K × x/(1 − x), with a high linear correlation coefficient, Rl = 0.9996, which permits quantitative SIMS analysis of relatively thick AlGaN barrier layers. The method of profile reconstruction with allowance for the main artifacts of ion sputtering has been first applied for the analysis of GaN/AlGaN/AlN/GaN high electron mobility transistor structure. This method permits to perform quantitative analysis of the thickness and composition of a nanometer-thin AlN sublayer and to estimate the measurement error. For the structure being studied, the AlN sublayer is 1.2 ± 0.2 nm thick. Copyright © 2016 John Wiley & Sons, Ltd.

Laser Ablation/Ionisation Mass Spectrometry: Sensitive and Quantitative Chemical Depth Profiling of Solid Materials.

Direct quantitative and sensitive chemical analysis of solid materials with high spatial resolution, both in lateral and vertical direction is of high importance in various fields of analytical research, ranging from in situ space research to the semiconductor industry. Accurate knowledge of the chemical composition of solid materials allows a better understanding of physical and chemical processes that formed/altered the material and allows e.g. to further improve these processes. So far, state-of-the-art techniques such as SIMS, LA-ICP-MS or GD-MS have been applied for chemical analyses in these fields of research. In this report we review the current measurement capability and the applicability of our Laser Ablation/Ionisation Mass Spectrometer (instrument name LMS) for the chemical analysis of solids with high spatial resolution. The most recent chemical analyses conducted on various solid materials, including e.g. alloys, fossils and meteorites are discussed.

Quantitative depth profiling of Si1–xGex structures by time-of-flight secondary ion mass spectrometry and secondary neutral mass spectrometry

Quantification of Ge in Si1–xGex structures (0.092≤x≤0.78) was carried out by time-of-flight secondary ion mass spectrometry (TOF-SIMS) and electron-gas secondary neutral mass spectrometry (SNMS). A good linear correlation (R2>0.9997) of the intensity ratios of secondary ions GeCs2+/SiCs2+ and 74Ge−/30Si− and post-ionized sputtered neutrals 70Ge+/28Si+ with Ge concentration was obtained. The calibration data were used for quantitative depth profiling of [10×(12.3nm Si0.63Ge0.37/34nm Si)] structures on Si. Satisfactory compliance of the quantified Ge concentration in SiGe layers with the values obtained by high-resolution X-ray diffraction was revealed for both techniques. SIMS and SNMS experimental profiles were fitted using Hofmann's mixing-roughness-information depth (MRI) model. In the case of TOF-SIMS, the quality of the reconstruction was better than for SNMS since not only the progressing roughening, but also the crater effect and other processes unaccounted in the MRI simulation could have a significant impact on plasma sputter depth profiling.

Towards Structural Analysis of Polymeric Contaminants in Electrodeposited Cu films

The incorporation of plating additives into Cu films was studied by means of complementary Laser Ablation/Ionization Mass Spectrometry (LIMS) and Secondary Ion Mass Spectrometry (SIMS) depth profiling techniques combined with Focused Ion Beam (FIB) analysis.Cu test samples were electrodeposited in the presence of a new prototypical two-component additive package for advanced Damascene applications consisting of a hybrid-type suppressor additive (Imep: polymerizate of epichlorohydrin and imidazole) and its essential co-additive (SPS: bis-(sodium-sulfopropyl)-disulfide). The tunable non-linear interplay between the Imep and the SPS during oscillatory Cu electrodeposition is used to fabricate samples bearing spatially confined layers with sequential high and marginal additive embedment. These test samples constitute an excellent platform to conduct true quantitative chemical depth profiling analysis of electrodeposited Cu films. In particular LIMS depth profiling measurements with an unmatched nano-meter depth-resolution demonstrate a preferential inclusion and accumulation of contaminants at grain boundaries inside the Cu deposit whereas the Cu grains remain largely contamination-free. A novel LIMS desorption approach is presented which allows for a molecular structure analysis of the polymeric additive ensembles preferentially embedded at grain boundaries of the Cu deposit. Our LIMS analysis confirms a recently discussed mechanism on the action of these hybrid additives which relies on their interaction with thiolate-stabilized Cu(I) intermediates.

Sulfur Transformation in Microbially Mediated Pyrite Oxidation by Acidithiobacillus ferrooxidans: Insights From X-ray Photoelectron Spectroscopy-Based Quantitative Depth Profiling

The oxidation of pyrite and other sulfides is responsible for the generation of acid mine drainage and acid rock drainage, which leads to further contamination of soil and water. In these processes, microbial oxidation usually prevails over chemical oxidation. To determine the mechanism of microbial oxidation of pyrite, the interaction of Acidithiobacillus ferrooxidans with pyrite was comprehensively studied, and the sulfur transformation in the interaction was disclosed using X-ray photoelectron spectroscopy (XPS) depth profiling. Abundant bacterial cells attach to pyrite surface and form biofilms, which greatly enhances surface corrosion and results in two types of etching pits: bacteria-driven rod-shaped and chemically driven hexagonal etching pits. The details of XPS depth profiles on a reacted pyrite surface reveal that the surface sulfur was first oxidized into elemental sulfur. Thereafter, elemental sulfur was further oxidized to intermediate species S2O32−, SO32−, and ultimately to SO42−. The oxidation sequence of sulfur is S22−/S2−→Sn2−, S0→SO32−, and S2O32−→SO42−. Meanwhile, the remnant ferrous iron in the surface layer was released into solution and subsequently oxidized into Fe3+ by A. ferrooxidans and dissolved oxygen, which in turn enhanced the oxidation of sulfur. Fe3+, sulfate, and other ions (e.g., K+, Na+, NH4+) in the solution precipitated as jarosite, hydroniumjarosite, and ammoniojarosite. On the basis of results, a three-staged model is proposed to interpret the kinetics of microbial oxidation of pyrite.

应力测量方法

本文对应力测量方法进行了评述和展望。主要介绍了多种传统测量应力的方法及原理，如小孔法、X射线衍射法、磁测法、超声波法、裂纹柔度等方法。并且提出了潜在可以用来表征薄膜界面间应力的一种新方法——溅射深度剖析定量分析。 The methods for stress measurement are reviewed and discussed, focusing on the principles and application of several traditional methods, such as Hole method, X-ray diffraction method, Magnetic method, Ultrasonic method, crack compliance method and so on. A new promising method, quantitative sputter depth profiling, is proposed for characterizing the stress gradient at interface.

Effect of water on solid electrolyte interphase formation in Li-ion batteries

Time-of-flight-elastic recoil detection analysis (TOF-ERDA) with 20MeV Cu ions has been applied to measure the depth profiles of solid electrolyte interphase (SEI) layers on the negative electrode of lithium ion batteries (LIB). In order to obtain quantitative depth profiles, the detector efficiency was first assessed, and the test highlighted a strong mass and energy dependence of the recoiled particles, especially H and He. Subsequently, we prepared LIB cells with different water contents in the electrolyte, and subjected them to different charge–discharge cycle tests. TOF-ERDA, X-ray photoelectron spectrometry (XPS), gas chromatography (GC), ion chromatography (IC), and 1H nuclear magnetic resonance (1H NMR) were applied to characterize the SEI region of the negative electrode. The results showed that the SEI layer is formed after 300 cycle tests, and a 500ppm water concentration in the electrolyte does not appear to cause significant differences in the elemental and organic content of the SEI.

Determination of molecular stopping cross section of 12C, 16O, 28Si, 35Cl, 58Ni, 79Br, and 127I in silicon nitride

Silicon nitride is a technologically important material in a range of applications due to a combination of important properties. Ion beam analysis techniques, and in particular, heavy ion elastic recoil detection analysis can be used to determine the stoichiometry of silicon nitride films, which often deviates from the ideal Si3N4, as well as the content of impurities such as hydrogen, even in the presence of other materials or in a matrix containing heavier elements. Accurate quantification of IBA results depends on the basic data used in the data analysis. Quantitative depth profiling relies on the knowledge of the stopping power cross sections of the materials studied for the ions involved, which in the case of HI-ERDA is both the primary beam, and the recoiled species. We measured the stopping cross section of 12C, 16O, 28Si, 35Cl, 58Ni, 79Br, and 127I in a well-characterised silicon nitride membrane. The measurements were made by independent groups utilising different experimental setups and methods. In some cases there is extensive overlap of the energy range in different experiments, allowing a comparison of the different results. The four independent data sets reported in this work are in excellent agreement with each other, in the cases where similar energy ranges were measured. On the other hand, the data are in most cases higher than calculations made with the interpolative schemes SRIM and MSTAR together with the Bragg rule. Better agreement is found with MSTAR in some of the cases studied. This work is a significant extension of the heavy ion stopping power data base for silicon nitride.

Investigation of the depth-profiling capabilities of the Storing Matter technique.

The so-called Storing Matter technique allows the matrix effect observed in secondary ion mass spectrometry to be successfully circumvented. We therefore investigate in this work the depth-profiling capabilities of the Storing Matter technique with a goal of developing protocols for quantitative depth profiles. The effect of the steps involved in the Storing Matter process on the main parameters such as the depth resolution and the dynamic range is studied experimentally and by simulations. A semi-automated process consisting of the sputter-deposition process on a rotating collector in the Storing Matter instrument followed by a complete analysis of the collector by secondary ion mass spectrometry is defined. This protocol is applied to depth profile a B implant in Si and a Sn/Zn multilayered sample, and the results are compared with those obtained with conventional secondary ion mass spectrometry.

Implementation of heavy-ion elastic recoil detection analysis at JANNUS-Saclay for quantitative helium depth profiling

Quantitative depth profiling measurements of implanted light elements is an important issue for electronics and nuclear applications. Conventional elastic recoil detection analysis (ERDA) has been improved by using heavy ions as incident particles for quantitatively profiling helium in materials.A new system has been implemented on the triple beam irradiation platform JANNUS at Saclay devoted to carry out HI-ERDA measurements. This device is dedicated to helium depth profiling using a 15MeV 16O5+ incident ion beam. Capabilities of the technique (quantitative analysis, resolution and limit of detection) were tested on samples of known composition.For the first time, 4He depth profiles in pure α-iron, as-implanted and annealed, are obtained. HI-ERDA measurements have shown that helium release in pure α-iron can be described by a succession of two steps, the first having a slow kinetics below 700°C and the second with a fast kinetics above 700°C.

Towards Quantification of Contaminants in Electrodeposited Cu Films

A Cu electroplating process is typically used in semiconductor industry for the on-chip fabrication of interconnects on non-planar (patterned) wafer surfaces with feature dimensions ranging from the sub-10nm level (advanced Damascene applications) up to the micrometer level (Through Silicon Via technology). The presence of particular additives in the plating bath during the electroplating is a crucial prerequisite for the successful fill of vias and trenches with Cu. The accumulation of contaminants in the resulting Cu film is known to significantly decelerate the post-deposition recrystallization that is mandatory to improve the conductivity of these interconnects. It is therefore vital to develop new analytical techniques allowing a precise (true) quantification of the contamination level in the Cu deposit. Classical Secondary Ion Mass Spectrometry (SIMS) depth profiling approaches only provide semi-quantitative information on the contamination level with a poor depth resolution. In this contribution we report on a recently developed quantitative depth profiling technique with sub-nanometer depth resolution based on laser ablation ionization mass spectrometry (LIMS). The high vertical depth resolution, a high dynamic range >108 coupled with a high detection sensitivity of ~ 10 ppb allows the identification/quantification of trace amounts of contaminants localized at grain boundaries of the Cu deposit. Results of the LIMS techniques are compared with complementary 3D atom probe tomography experiments. To demonstrate the capabilities of these analytical techniques we use copper films electrodeposited in the presence of SPS (bis-(sodium-sulfopropyl)-disulfide) and Imep (polymerizates of imidazole and epichlorohydrin) additives as model system. This approach allows the targeted insertion of grain boundaries into the Cu film perpendicular to the growth (depth profiling) direction.

Quantitative detection of caffeine in human skin by confocal Raman spectroscopy – A systematic in vitro validation study

For rational development and evaluation of dermal drug delivery, the knowledge of rate and extent of substance penetration into the human skin is essential. However, current analytical procedures are destructive, labor intense and lack a defined spatial resolution. In this context, confocal Raman microscopy bares the potential to overcome current limitations in drug depth profiling. Confocal Raman microscopy already proved its suitability for the acquisition of qualitative penetration profiles, but a comprehensive investigation regarding its suitability for quantitative measurements inside the human skin is still missing.In this work, we present a systematic validation study to deploy confocal Raman microscopy for quantitative drug depth profiling in human skin. After we validated our Raman microscopic setup, we successfully established an experimental procedure that allows correlating the Raman signal of a model drug with its controlled concentration in human skin. To overcome current drawbacks in drug depth profiling, we evaluated different modes of peak correlation for quantitative Raman measurements and offer a suitable operating procedure for quantitative drug depth profiling in human skin.In conclusion, we successfully demonstrate the potential of confocal Raman microscopy for quantitative drug depth profiling in human skin as valuable alternative to destructive state-of-the-art techniques.

Development of laser induced breakdown spectroscopy for studying erosion, deposition, and fuel retention in ASDEX Upgrade

The paper deals with the development of laser induced breakdown spectroscopy (LIBS) into an in situ method for studying erosion/deposition processes at the first walls of fusion reactors. To this end, samples extracted from the divertor tiles of ASDEX Upgrade after the 2009 plasma operations were analyzed using LIBS for their composition and the results were compared with other post mortem deposition data. Quantitative depth profiles for the elemental concentrations were extracted from LIBS spectra by applying a novel data processing method. In addition, both multiline and multispot averaging procedures were applied to reduce fluctuations in the data. The LIBS concentration profiles matched qualitatively with those given by secondary ion mass spectrometry and quantitatively with the ion-beam data. The deuterium content of the samples could be reliably determined if the surface densities were >1017at/cm2.