Secondary Ion Mass Spectrometry Profiles Research Articles

Exploring chitosan-plant extract bilayer coatings: Advancements in active food packaging via polypropylene modification

UV-ozone activated polypropylene (PP) food films were subjected to a novel bilayer coating process involving primary or quaternary chitosan (CH/QCH) as the first layer and natural extracts from juniper needles (Juniperus oxycedrus; JUN) or blackberry leaves (Rubus fruticosus; BBL) as the second layer. This innovative approach aims to redefine active packaging (AP) development. Through a detailed analysis by surface characterization and bioactivity assessments (i.e., antioxidant and antimicrobial functionalities), we evaluated different coating combinations. Furthermore, we investigated the stability and barrier characteristics inherent in these coatings. The confirmed deposition, coupled with a comprehensive characterization of their composition and morphology, underscored the efficacy of the coatings. Our investigation included wettability assessment via contact angle (CA) measurements, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), which revealed substantial enhancements in surface concentrations of elements and functional groups of CH, QCH, JUN, and BBL. Scanning electron microscopy (SEM) unveiled the coatings' heterogeneity, while time-of-flight secondary ion mass spectrometry (ToF-SIMS) and CA profiling showed moderately compact bilayers on PP, providing active species on the hydrophilic surface, respectively. The coatings significantly reduced the oxygen permeability. Additionally, single-layer depositions of CH and QCH remained below the overall migration limit (OML). Remarkably, the coatings exhibited robust antioxidative properties due to plant extracts and exceptional antimicrobial activity against S. aureus, attributed to QCH. These findings underscore the pivotal role of film surface properties in governing bioactive characteristics and offer a promising pathway for enhancing food packaging functionality.

Quantification of secondary ion mass spectrometry measurements by using ion‐implanted metallic standards

This research addresses an analytical methodology to quantify elements of interest in fusion‐relevant materials using secondary ion mass spectrometry (SIMS). For this purpose, internal standards have been fabricated by ion implantation to avoid the well‐known matrix effect of this technique. In particular, chromium has been implanted at an energy of 12 MeV using two fluences in high‐purity iron and tungsten matrices together with Si control substrates. The latter were applied to determine the Cr concentration implanted through experimental and semiempirical methods. Specifically, the IBA technique Rutherford backscattering spectrometry (RBS) provided the quantitative results being 3.1 × 1019 at/cm3 and 1.6 × 1019 at/cm3 for the high and low dose, respectively. The SIMS depth profiles of Cr for the Fe and W matrices established an ion implantation depth close to 2 μm on both substrates in agreement with the calculations previously performed by Stopping and Range of Ions in Matter (SRIM) simulations. Correlation between the integration of SIMS profiles and known concentrations of the implanted ion resulted in the calibration curve for each matrix, obtaining the SIMS quantification approach by means of this relative sensitivity factor (RSF). Additionally, a cross‐check of the method by comparing commercial Fe‐Cr alloys with the Cr‐implanted Fe matrices of the present study pointed out the need to produce standards with higher chromium concentrations.

Diffusion models of grown-in and implanted p-type dopant in III-V semiconductor compounds

This research shows that the diffusion of grown-in and implanted Be atoms in III-V considered semiconductor materials, such as the Liquid-Encapsulated Czochralski-grown (LEC) GaAs as well as the Gas-Source Molecular Beam Epitaxy (GSMBE) In0.53Ga0.47As, In0.73Ga0.27As0.58P0.42, In0.53Ga0.47As/In0.73Ga0.27As0.58P0.42, In0.53Ga0.47As/InP compounds, taking place during the Rapid Thermal Annealing (RTA) process, is perfectly well explained by the “full” version of the kick-out mechanism operating through singly positively ionized Be interstitials and group III self-interstitial ions (Ga, In) in all their states of positive charge including neutral. Numerical solutions of the differential equations, corresponding to the considered system of diffusion reactions, have been calculated using the finite difference approach and our elaborate finite difference-Bairstow method. Such a model naturally emerges from most research works, including ours, in the considered field, over the last decades and makes it possible to “reconcile” their different diffusion models. In this study, we also present and analyze the Secondary Ion Mass Spectrometry (SIMS) profiles of the distribution of implanted Be in GaAs at an energy of 100 keV with a high dose of 1.0 ⋅ 1015cm−2 and annealed at temperatures ranging from 700 to 850 °C for à time ranging from 60 to 240s.

Artifact-free secondary ion mass spectrometry profiling of a full vertical cavity surface emitting laser structure

The optimization of the structure of vertical-cavity surface-emitting lasers (VCSELs) is required to produce more efficient devices. The secondary ion mass spectrometry (SIMS) technique can provide information about the structure and the distribution of dopants and contaminants. However, VCSELs are relatively thick, contain hundreds of layers with varying compositions, and consist of very thin layers. Classical SIMS is prone to artifacts which decreases the quality of the results. In this work, modifications of the SIMS measurement procedures are presented: high incident angle bombardment reduces the mixing effect; optimization of the extraction parameters increases the signal-to-noise ratio from 2.1 to 24.3 dB; Ion polishing and beam service preserves the quality of the measurement. Due to impact energy modulations quantum wells and barriers are registered as box-shaped features. The raw data is free of artifacts and reflects the realistic distribution of elements. Such accuracy may prove invaluable for further optimization of VCSELs.

Effects of Silane Monolayers on Lysophosphatidylcholine (LysoPC) Detection by Desorption Ionization on Silicon Mass Spectrometry (DIOS-MS) in Solution and Plasma

Desorption ionization on silicon mass spectrometry (DIOS-MS) enables high throughput analysis of low-molecular-weight biomolecules. However, detection of metabolite biomarkers in complex fluids such as plasma requires sample pretreatment, limiting clinical application. Here, we show that porous silicon, chemically modified using monolayers of n-propyldimethylmethoxysilane molecules, is a good candidate for fingerprinting lysophosphatidylcholine (lysoPC) in plasma, without sample pretreatment, for DIOS-MS-based diagnosis (e.g., sepsis). Results were correlated to lysoPC molecule location inside/outside the pores, determined by time-of-flight secondary ion mass spectrometry profiling, and to physicochemical properties.

Molecular beam homoepitaxy of N-polar AlN on bulk AlN substrates

N-polar AlN epilayers were grown on the N-face of single-crystal bulk AlN substrates by plasma-assisted molecular beam epitaxy. A combination of in situ thermal deoxidation and Al-assisted thermal desorption at high temperature aided in removing native surface oxides and impurities from the N-polar surface of the substrate enabling successful homoepitaxy. Subsequent epitaxial growth of the AlN layer on the in situ cleaned substrates, grown in a sufficiently high Al droplet regime, exhibited smooth surface morphologies with clean and wide atomic steps. KOH etch studies confirmed the N-polarity of the homoepitaxial films. Secondary ion mass spectrometry profiles show Si and H impurity concentrations below the noise levels, whereas O and C impurity concentrations of ∼8×1017 and ∼2×1017 atoms/cm3 are observed, respectively. Although the structural defect densities are low, they interestingly appear as inversion domains of different dimensionalities.

Growth morphology and phase composition of hierarchically self-organized oxyspinel composite films deposited by radio frequency magnetron sputtering

Multicomponent Al 0.1 Si 0,05 Ti 0,1 Mn 1.45 Co 0.7 Ni 0.6 O 4 oxyspinel solid solution ceramics was synthesized to be subsequently used as a target for the deposition of thin films onto silicon and metallized silicon substrates by means of radio frequency sputtering method. Temporal evolution of chemical and phase compositions of the deposited layers, as well as their structure and surface morphology for the different substrate temperatures, have been systematically investigated using energy dispersive X-ray (EDS) analysis, secondary ion mass spectroscopy (SIMS) profiling, Raman spectroscopy, and atomic force microscopy (AFM). The samples revealed a uniform chemical composition throughout their whole depth, corresponding well with the formula unit of the spinel. Across the film depth, progressive developing of a self-organized, two-scale hierarchical composite structure was observed, which is composed of the main oxide grains decorated with spinel nanocrystallites.

Optical properties and formation kinetics of corrosion inhibitor films at the Cu/[formula omitted]/[formula omitted] interface

Optical properties in the wavelength range of visible light and the growth kinetics of films composed of cuprous oxide (Cu2O) and benzotriazole, 2-mercaptobenzothiazole, 2-mercapto-1-methylimidazole, 2-methylimidazole and 4-methylimidazole, on a polished copper surface in the presence of the neutral 3wt% NaCl solution open to air, are studied by the in-situ spectroscopic ellipsometry, and compared with the secondary ion mass spectrometry profiles, as well as their corrosion protectiveness established from cyclic voltammetry. The optical properties of the growing films are determined by the dielectric function (DF), which is fitted from the ellipsometric spectra by employing an optical model based on Bruggemans effective medium approximation. This enables distinguishing the organic from the Cu2O component as well as the surface roughness or porosity, naturally occurring at the polished Cu surfaces. As the main result, the film thickness increase and the variation of the volume fractions of the optical components are driven into relationship with the chemical composition, providing a detailed picture of the material structuring upon film growth. The DFs are discussed in the light of optoelectronic parameters (absorption coefficient and electronic band gap energy) as well as corrosion protectiveness of the studied films, whereupon a clear correlation among these properties is established.

Chemical Reaction and Bonding Mechanism at the Polymer-Metal Interface.

Polymer-metal hybrid structures have attracted significant attention recently due to their advantage of great weight reduction and excellent integrated physical/chemical properties. However, due to great physicochemical differences between polymers and metals, obtaining an interface with high bonding strength is a challenge, which makes it critically important to clarify the underlying bonding mechanisms. In the present research, we focused on revealing the underlying bonding mechanisms of a laminated Cr-coated steel-ethylene acrylic acid (EAA) strip prepared by hot roll bonding from the microscale to the molecular scale with experimental evidence. The microscale mechanical interlocking was analyzed and proven by scanning white light interferometry and scanning electron microscopy (SEM) by means of observing the surface and cross-sectional morphologies. Additionally, interfacial phases and chemical compositions were analyzed by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). More directly and effectively, the interface was successfully exposed for X-ray photoelectron spectroscopy (XPS) analysis. Combined with time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and depth profiling analysis, the formation of -(O═)C-O-Cr and -C-(O-Cr)2 covalent bonds through chemical reactions at the interface between -COOH and Cr2O3 was verified. Based on these characterization results, interfacial bonding mechanisms for the laminated Cr-coated steel-EAA strip were clearly identified to be chemical bonding and micromechanical interlocking, along with hydrogen bonding, which were all demonstrated with solid experimental evidence. In addition, 3D-render view and cross-section images of typical ion fragments at the interface were used to reveal the interfacial structure more comprehensively. The contributions of hydrogen bonds and covalent bonds to the interface were evaluated and compared for the first time. This study provides both methodological and theoretical guidance for investigating and understanding interfacial bonding formation in polymer-metal hybrid structures.

Time of Flight – Secondary Ion Mass Spectroscopy Profiling of Self-Assembled Monolayer Patterns Based on Vapor Deposition Technique

It is crucial to develop novel metrology techniques in a semiconductor fabrication process for characterizing a thin film with a thickness of a few nanometers, as well as the material profile of the film accurately. Uniform trichlorosilane (1H,1H,2H,2H-perfluorodecyltrichlorosilane) derived self-assembled monolayer film patterns were fabricated by several conventional semiconductor fabrication techniques incorporated, including photolithography, vapor deposition, and lift-off technique. The patterned trichlorosilane self-assembled monolayer patterns were thoroughly characterized by Time-of-Flight Secondary Ion Mass Spectrometry, and precise two-dimensional self-assembled monolayer patterns were reconstructed through corresponding ions and ion clusters feature peaks. Additionally, three-dimensional self-assembled monolayer patterns were reconstructed layer by layer through gas cluster ion beam etching and two-dimensional mapping analysis in an alternate way, which verifies that vapor-based trichlorosilane self-assembled monolayer patterns were precisely fabricated and Time-of-Flight Secondary Ion Mass Spectrometry is highly surface-sensitive to obtain accurate information about the self-assembled monolayer pattern in a point-by-point manner. Time-of-Flight Secondary Ion Mass Spectrometry technique could be used as a metrology technique in the semiconductor process with high-quality self-assembled monolayer micro and nanostructures.

Doping profiling of beveled Si wafers via UV-micro Raman spectroscopy

Doping profiling methods are required to provide doping monitoring of heavy doped Silicon wafers, widely used in electronic devices, with high concentration sensitivity and spatial resolution. Herein, we demonstrate that ultraviolet (UV) micro-Raman spectroscopy implemented on small-angle beveled surfaces is able to produce a Raman-based doping profile without any further measurements. The reliability of the approach is verified on ion-implanted p-type B-doped single-crystalline Si (100) wafers with shallow (100 nm) doping profile, directly comparing the Raman-based doping profiling results with independent secondary ion mass spectrometry (SIMS) and spreading resistance profiling (SRP) measurements. The Raman-based technique is capable to fully reproduce the doping profile down to 100 nm with excellent doping sensitivity (10 ppm) in the 1018–1020 cm−3 doping concentration range providing high lateral (vertical) resolution of 1μm (10 nm). The technique is comparable to SIMS in terms of resolution and sensitivity down to 1018 cm−3 concentration but requires the beveling process. Instead, it is a better alternative to SRP on bevel due to its higher spatial resolution and avoiding probe contact. The Raman-based doping profiling technique is, therefore, suitable for heavy doped Si with typical shallow doping profiles of state-of-the-art Si-based nanoelectronics.

The Effect of Nanometer‐Scale V‐Pit Layer on the Carrier Recombination Mechanisms and Efficiency Droop of GaN‐Based Green Light‐Emitting Diodes

The effects of nanometer‐scale V‐pits layer with different parameters on the carrier recombination mechanisms and efficiency droop of GaN‐based green light‐emitting diodes (LEDs) are investigated. Under optimized growth conditions, the threading dislocations (TDs) are surrounded by V‐pits layer with six (10–11) side wall facets. The V‐pits layer contains sidewall multiple quantum wells (MQWs) with bandgap several hundred millielectronvolts higher than that of c‐plane MQWs. This higher bandgap acts as a barrier for carriers and prevents them from reaching the dislocations, which can effectively suppress the nonradiative recombination. Analysis suggests that the V‐pits enhance hole injection into deeper MQWs, which is confirmed by the secondary ion mass spectroscopy profiles of Mg and Al. With the aid of the V‐pits layer, holes can be injected into deeper MQWs, which reduce the carrier concentration within individual QWs. Therefore, the Auger‐related efficiency droop can be suppressed. The results show that LED with 200 nm LT‐GaN + 40 nm n‐GaN V‐pits layer is able to deliver an improvement in the light output power by 189% as compared with reference LED without V‐pits layer. At 200 mA, the efficiency droop for LED with200 nm LT‐GaN + 40 nm n‐GaN V‐pits is 25.9%, which is much smaller than 34.7% for reference LED without V‐pits.

Detrimental Impact of Na Upon Rb Postdeposition Treatments of Cu(In,Ga)Se2 Absorber Layers

Passivation of the Cu(In,Ga)Se2 (CIGS)/Mo back contact using AlO x is studied to reduce the recombination at this interface. Herein, RbF postdeposition treatment (RbF‐PDT), a well‐established method to improve absorber and front interface properties is used on back‐passivated solar cells. It is found that this combination deteriorates the performance due to formation of an injection barrier at the front and reduced acceptor concentration. Photoluminescence yield and decay times show no indication of increased defect recombination, as both are improved. With time‐of‐flight secondary ion mass spectroscopy, in‐depth and lateral alkali profiles are measured. It is shown that the Na concentration is higher at the AlO x /Mo back contact and that Rb accumulates at the CdS/CIGS interface. It is hypothesized that Na at the back is released during the RbF‐PDT and inhibits Rb diffusion into the CIGS layer. Rb remains at the front and acceptor concentration is reduced. Modeling of dark and light current–voltage characteristics shows that the injection barrier and low doping are responsible for the reduced V oc and fill factor (FF). It is suggested that the commonly observed FF losses upon heavier alkali PDT can be eliminated by adapting the initial Na amount.

Characterization and role of deep traps on the radio frequency performances of high resistivity substrates

In this study, high-resistivity gold-implanted silicon substrates developed for radio frequency (RF) applications were characterized. By varying PICTS (Photo-Induced Current Transient Spectroscopy) measurement conditions such as the illumination wavelength, we identified the signature and the nature of four dominant traps. Two were electron traps and the others were hole traps. All of the related defects involved gold atoms. RF simulations of coplanar waveguide transmission lines integrated on these substrates were carried out, based on the trap properties extracted from PICTS results. A good agreement between RF experimental data and simulations was achieved by tuning the trap concentrations. Finally, the gold density extracted from the fit was successfully compared with the secondary ion mass spectrometry profile and an explanation of the role of the traps in RF behavior of the substrate was given.

Identification by deuterium diffusion of a nitrogen-related deep donor preventing the p-type doping of ZnO

Deuterium diffusion is investigated in nitrogen-doped homoepitaxial ZnO layers. The samples were grown under slightly Zn-rich growth conditions by plasma-assisted molecular beam epitaxy on m-plane ZnO substrates and have a nitrogen content [N] varied up to 5 × 1018 at cm−3 as measured by secondary ion mass spectrometry (SIMS). All were exposed to a radio frequency deuterium plasma during 1 h at room temperature. Deuterium diffusion is observed in all epilayers, while its penetration depth decreases as the nitrogen concentration increases. This is strong evidence of a diffusion mechanism limited by the trapping of deuterium on a nitrogen-related trap. The SIMS profiles are analyzed using a two-trap model including a shallow trap, associated with a fast diffusion, and a deep trap, related to nitrogen. The capture radius of the nitrogen-related trap is determined to be 20 times smaller than the value expected for nitrogen–deuterium pairs formed by coulombic attraction between D+ and nitrogen-related acceptors. The (N2)O deep donor is proposed as the deep trapping site for deuterium and accounts well for the small capture radius and the observed photoluminescence quenching and recovery after deuteration of the ZnO:N epilayers. It is also found that this defect is by far the N-related defect with the highest concentration in the studied samples.

The impact of deposition and annealing temperature on the growth properties and surface passivation of silicon dioxide films obtained by atomic layer deposition

This paper studies the impact of deposition and annealing temperature on the growth properties and surface passivation of silicon dioxide (SiO2) films obtained by atomic layer deposition (ALD) using tris(dimethylamino)-silane (TDMAS) precursor. Increasing in deposition temperature from 200 to 350 °C alters the growth rate and refractive index significantly. The ALD-SiO2 films deposited at over 250 °C obtain excellent surface passivation after annealing at 650 °C, which could be explained by the synergistic effects of chemical and field-effect passivation caused by low interface defect states density (Dit) and high positive fixed charges density (Qf), respectively. Meanwhile, the effect of deposition temperature on surface passivation depends on the extent of TDMAS chemical adsorption and dissociation during ALD. X-ray photoelectron spectroscopy (XPS) shows low temperature as-deposited SiO2 films contain higher carbon impurities because of the remained dimethylamine groups. Regarding the impact of annealing temperature on surface passivation, secondary ion mass spectroscopy profiles and XPS results reveal that high-temperature annealing probably forms more hydrogen and oxygen vacancies at SiO2/Si interface, causing a decrease in Dit and an increase in positive Qf, respectively. This work provides a reference for applying ALD-SiO2 films to surface passivation technology of crystalline silicon solar cells.

Atom probe tomography quantification of carbon in silicon

Atom Probe Tomography (APT) was used to quantify carbon in implanted silicon at two various electric fields (~ 15 and 20 V/nm). Using equal proportions of implanted 12C and 13C, the numerous molecular ions that were observed were identified and their contribution to the carbon content statistically derived. Much more accurate carbon quantification was obtained in the lowest electric field analysis by comparing APT with Secondary Ion Mass Spectroscopy profiles. This was assigned to a lower amount of molecular ion dissociations. Furthermore, the number of self-interstitials trapped per carbon atom in clusters was derived. This value of interest for the microelectronics industry regarding dopant diffusion and implantation induced defects was estimated close to one, in agreement with the expected stoichiometry of the SiC phase present in the phase diagram. However, this was obtained only when using low electric field conditions.

Role of ZnS Particles in the Performance of Cu2ZnSnS4 Thin Film Solar Cells: A Comparative Study by Active Control of Zinc Deposition in Coevaporated Precursors

Formation of ZnS particles in the Cu2ZnSnS4 (CZTS) light absorber layer of CZTS solar cells may impede the photocarrier collection as well as the open circuit voltage. Coevaporation of Cu, Zn, Sn, and S elements can provide a uniform and well‐mixed Cu–Zn–Sn–S precursor at atomic level, yet the annealing/sulfurization process does not preserve such elemental distribution. The Zn element in the formed CZTS absorber thin films from such a uniform precursor distributes unevenly, especially aggregating near the rear interface, and thus deteriorates the film quality. Herein, the movement pathway of the Zn element in the coevaporated precursor during annealing is investigated through energy dispersive X‐ray spectroscopy (EDX) mapping and secondary ion mass spectroscopy (SIMS) profiling. With the understanding of the segregation behavior of the Zn element, an active manipulation of the initial distribution of Zn in the precursor is accordingly designed to effectively alleviate the accumulation of Zn near the rear Mo/CZTS interface and therefore improve the crystalline quality of the absorber. The results suggest that properly controlling the precursor.

Higher Operating Temperature IR Detectors of the MOCVD Grown HgCdTe Heterostructures

This paper summarizes progress in metal organic chemical vapour deposition (MOCVD) technology achieved in recent years at the Institute of Applied Physics, Military University of Technology and VIGO System S.A. MOCVD with a wide range of composition and donor/acceptor doping and without post-growth annealing is a very convenient tool for the deposition of HgCdTe epilayers used for uncooled infrared detectors. Particular attention is focused on: surface morphology improvement, doping issues, diffusion processes during growth study, substrate issues, crystallographic orientation selection. In this respect, MOCVD technology improvement influencing IR detector parameters is shown. CdTe buffer layer deposition allows HgCdTe heterostructure growth on GaAs substrates. Theoretical modelling using APSYS platform supports designing and better understanding of the carrier transport mechanism in detector’s structures. Secondary ion mass spectrometry profiles allows to compare projected and obtained structures and revealed diffusion processes of the elements. A wide range of different types of infrared detectors operating at high operating temperature conditions has been constructed: photoresistors, non-equilibrium photodiodes, dual-band photodiodes, barrier and multiple detectors. The methodical research efforts contributed to the time constant reduction are important in many detector applications. Future challenges and prospects are also discussed.

Surface control and MBE growth diagram for homoepitaxy on single-crystal AlN substrates

The evolution of surface morphology for single-crystal bulk Al-polar aluminum nitride substrates during ex situ cleaning, in situ cleaning, and subsequent homoepitaxy is investigated. Ex situ acid treatment is found to reveal atomic steps on the bulk AlN substrates. After in situ Al-assisted cleaning at high temperatures in a high vacuum environment monitored with reflection high-energy electron diffraction, cleaner atomic step edges are observed. Subsequent growth on the cleaned bulk AlN by molecular beam epitaxy is used to develop a phase-diagram for homoepitaxy on AlN single crystals. Secondary ion mass spectrometry profiles reveal high-purity epitaxial layers with undesired chemical impurity densities of Si, O, and C to be below detection limits. The grown homoepitaxial films are observed to oxidize in the ambient environment, but repeating the ex situ acid treatment again reveals atomic steps.