Analyse par ToF-SIMS de matériaux organiques pour les applications en électronique organique

During the last decade, organic electronics have developed rapidly. However, the production of organic electronic devices is still impeded because of various technological barriers. Such systems have specific analytical needs and time-of-flight secondary ion mass spectrometry (ToF-SIMS) is per se highly relevant, particularly when considering the use of a new type of ion source based on argon clusters (Arn +). The main objective of this work was therefore to understand the ion-matter interactions of such a cluster beam with the organic materials used in organic electronics. A fundamental study was carried out by comparing sputtering with three different ion beams (Cs+, C60 ++, Arn +) on organic structured samples (such as PS-b-PMMA block copolymers) and it transpired that although cluster size and energy has little effect on the observable damage to the sample, larger argon clusters induce more roughness during ToFSIMS depth profiling. This was confirmed by AFM (Atomic Force Microscopy) and XPS (Xray Photoelectron Spectroscopy) and a geometric model. Next, different devices in organic electronics were characterized by ToF-SIMS. The study of self-assembling PS-b-PMMA block copolymers made possible to evaluate the influence of the annealing duration and of the thickness of the layer. Furthermore, a protocol was developed to analyse stacks of inorganic/organic layers, in particular those contained in OLED devices. It was then possible to characterize the stacks of a complete organic light-emitting device whilst maintaining molecular signal and a high depth resolution of 2 nm. In parallel we identified the chemical degradation of an organic material in the stack and evaluated the efficiency of barrier layers designed to protect it. More precisely, specific signatures to the hydrolysis reaction of the layer as well as increase in moisture level after encapsulation were identifiedL'électronique organique a connu durant la dernière décennie un essor considérable. La production de dispositifs à base de matériaux organiques reste néanmoins freinée par différents verrous technologiques. La caractérisation de ce type de systèmes conduit à des besoins analytiques spécifiques et la spectrométrie de masse des ions secondaires à temps de vol (Timeof-Flight Secondary Ion Mass Spectrometry – ToF SIMS) est a priori très pertinente notamment grâce à l'utilisation d'un nouveau type de faisceau d'ions à base d'agrégats d'argon (Arn +). L'objectif principal de ce travail a donc été de comprendre l'interaction ions-matière d'un tel faisceau avec les matériaux organiques utilisés en électronique organique. Une étude fondamentale a d'abord été réalisée en comparant différents faisceaux d'ions de décapage (Cs+, C60 ++, Arn +) sur des échantillons organiques structurés (tels que les copolymères à blocs PS-b-PMMA) et il est apparu que, bien que la taille des agrégats et leur énergie ont peu d'effet sur l'endommagement observable sur les échantillons, les agrégats d'argon de grande taille induisent de la rugosité lors du profil en profondeur ToF SIMS, sans modification chimique, ce qui a été confirmé par des analyses complémentaires – AFM (Atomic Force Microscopy) et XPS (X-ray Photoelectron Spectroscopy) – et une modélisation géométrique. Ensuite, différents dispositifs du domaine de l'électronique organique ont été caractérisés. Ainsi, l'étude de l'auto structuration des copolymères à blocs PS-b-PMMA a permis d'évaluer l'influence du temps de recuit et de l'épaisseur de la couche. Par ailleurs, un protocole a été développé pour l'analyse d'empilements de couches inorganiques/organiques, notamment ceux des OLED. Il a ainsi été possible de caractériser par profil en profondeur ToF-SIMS les différents empilements d'un dispositif de l'électronique organique en conservant la détection d'un signal moléculaire et une haute résolution en profondeur de 2 nm. Parallèlement, nous avons identifié la dégradation chimique d'un matériau organique du multicouche constitutif de l'empilement et évalué la protection de celui-ci via des couches barrières. Plus précisément, les signatures de la réaction d'hydrolyse de la couche ont été identifiées ainsi que la teneur en humidité après encapsulatio

Time-resolved dissolution elucidates the mechanism of zeolite MFI crystallization

Zeolite crystal growth mechanisms are not fully elucidated owing to their complexity wherein the formation of a particular zeolite can occur by more than one crystallization pathway. Here, we have conducted time-resolved dissolution experiments of MFI-type zeolite crystals in ammonium fluoride medium where detailed structural analysis allowed us to extrapolate and elucidate the possible mechanism of nucleation and crystal growth. A combination of electron and scanning probe microscopy shows that dissolution initiates preferentially at lattice defects and progressively removes defect zones to reveal a mosaic structure of crystalline domains within each zeolite crystal. This mosaic architecture evolves during the growth process, reflecting the changing conditions of zeolite formation that can be retroactively assessed during zeolite crystal dissolution. Moreover, a more general implication of this study is the establishment that dissolution can be used successfully as an ex situ technique to uncover details about crystal growth features inaccessible by other methods

ToF-SIMS analysis of organic multilayers for organic electronic applications

L'électronique organique a connu durant la dernière décennie un essor considérable. La production de dispositifs à base de matériaux organiques reste néanmoins freinée par différents verrous technologiques. La caractérisation de ce type de systèmes conduit à des besoins analytiques spécifiques et la spectrométrie de masse des ions secondaires à temps de vol (Timeof-Flight Secondary Ion Mass Spectrometry – ToF SIMS) est a priori très pertinente notamment grâce à l'utilisation d'un nouveau type de faisceau d'ions à base d'agrégats d'argon (Arn +). L'objectif principal de ce travail a donc été de comprendre l'interaction ions-matière d'un tel faisceau avec les matériaux organiques utilisés en électronique organique. Une étude fondamentale a d'abord été réalisée en comparant différents faisceaux d'ions de décapage (Cs+, C60 ++, Arn +) sur des échantillons organiques structurés (tels que les copolymères à blocs PS-b-PMMA) et il est apparu que, bien que la taille des agrégats et leur énergie ont peu d'effet sur l'endommagement observable sur les échantillons, les agrégats d'argon de grande taille induisent de la rugosité lors du profil en profondeur ToF SIMS, sans modification chimique, ce qui a été confirmé par des analyses complémentaires – AFM (Atomic Force Microscopy) et XPS (X-ray Photoelectron Spectroscopy) – et une modélisation géométrique. Ensuite, différents dispositifs du domaine de l'électronique organique ont été caractérisés. Ainsi, l'étude de l'auto structuration des copolymères à blocs PS-b-PMMA a permis d'évaluer l'influence du temps de recuit et de l'épaisseur de la couche. Par ailleurs, un protocole a été développé pour l'analyse d'empilements de couches inorganiques/organiques, notamment ceux des OLED. Il a ainsi été possible de caractériser par profil en profondeur ToF-SIMS les différents empilements d'un dispositif de l'électronique organique en conservant la détection d'un signal moléculaire et une haute résolution en profondeur de 2 nm. Parallèlement, nous avons identifié la dégradation chimique d'un matériau organique du multicouche constitutif de l'empilement et évalué la protection de celui-ci via des couches barrières. Plus précisément, les signatures de la réaction d'hydrolyse de la couche ont été identifiées ainsi que la teneur en humidité après encapsulationDuring the last decade, organic electronics have developed rapidly. However, the production of organic electronic devices is still impeded because of various technological barriers. Such systems have specific analytical needs and time-of-flight secondary ion mass spectrometry (ToF-SIMS) is per se highly relevant, particularly when considering the use of a new type of ion source based on argon clusters (Arn +). The main objective of this work was therefore to understand the ion-matter interactions of such a cluster beam with the organic materials used in organic electronics. A fundamental study was carried out by comparing sputtering with three different ion beams (Cs+, C60 ++, Arn +) on organic structured samples (such as PS-b-PMMA block copolymers) and it transpired that although cluster size and energy has little effect on the observable damage to the sample, larger argon clusters induce more roughness during ToFSIMS depth profiling. This was confirmed by AFM (Atomic Force Microscopy) and XPS (Xray Photoelectron Spectroscopy) and a geometric model. Next, different devices in organic electronics were characterized by ToF-SIMS. The study of self-assembling PS-b-PMMA block copolymers made possible to evaluate the influence of the annealing duration and of the thickness of the layer. Furthermore, a protocol was developed to analyse stacks of inorganic/organic layers, in particular those contained in OLED devices. It was then possible to characterize the stacks of a complete organic light-emitting device whilst maintaining molecular signal and a high depth resolution of 2 nm. In parallel we identified the chemical degradation of an organic material in the stack and evaluated the efficiency of barrier layers designed to protect it. More precisely, specific signatures to the hydrolysis reaction of the layer as well as increase in moisture level after encapsulation were identifie

Characterization of advanced ALD-based thin film barriers for organic electronics using ToF-SIMS analysis

International audienceTo address all the concerns of organic electronics device development and especially ageing issues, analytical techniques must be able to provide extremely fine characterization of the composition and thickness of layers and interfaces, while retaining appropriate spatial resolution. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is able to provide a detailed characterization of the in-depth composition of hybrid organic/in-organic multilayer structures which is crucial for such investigations. The study of an aged AlQ(3) film after an exposition at the ambient atmosphere permitted to identify the secondary ions that are potentially indicative of the hydrolysis reaction of AlQ(3). The investigation of the organic/inorganic multilayer devices by ToF-SIMS depth profiling also confirmed a confinement of the moisture in the gas barrier layer(s). It was possible to determine the moisture ratio present in the different barrier architectures to compare the efficiency of the encapsulation. In particular, the double barrier layer has shown a lower and a more localized diffusion of the moisture in the barrier which was consistent with the results of the performance of the devices and with the data reported in the literature such as water vapor transmission rate ones

Comparative evaluation of intermediate solutions in prevention of brown precipitate formed from sodium hypochlorite and chlorhexidine gluconate

Abstract Objectives To evaluate intermediate treatments between sodium hypochlorite and chlorhexidine gluconate irrigations for the prevention of a toxic brown precipitate in root canal therapy. Materials and Methods Thirty‐nine premolars were irrigated with 6% sodium hypochlorite and divided into either: No intermediate treatment; Dry paper points; three different irrigations with 17% ethylenediaminetetraacetic acid, deionized water, or 5% sodium thiosulfate. 2% chlorhexidine gluconate was the final irrigant in all groups. Sectioned teeth were analyzed for brown precipitate intensity and area using stereomicroscopy and components related to para‐chloroaniline using Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS). Results Stereomicroscopy showed that 5% STS significantly reduced brown precipitate intensity and area as compared with no intermediate irrigation (p < .05, Chi‐square, generalized linear model, and Tukey's multiple comparison tests). Utilizing ToF‐SIMS, 5% sodium thiosulfate was most effective in reducing the components representing para‐chloroaniline and chlorhexidine gluconate. Conclusion The 5% sodium thiosulfate was most effective among other intermediate treatments, assessed by stereomicroscopy and ToF‐SIMS

ToF-SIMS Depth Profiling of PS- b -PMMA Block Copolymers Using Ar n + , C 60 ++ , and Cs + Sputtering Ions

International audienceTime-of-flight secondary ion mass spectrometry (ToF-SIMS) is a high performance tool for molecular depth profiling of polymer films, in particular when they are structured in microphases. However, a major issue is the degradation of polymer materials under ion irradiation in reactions such as cross-linking, chain breaking, or reorganization processes of polymers which have been demonstrated for materials such as polystyrene (PS) and poly(methyl methacrylate) (PMMA). This work aims at comparing ToF-SIMS molecular depth profiling of structured polymers (polystyrene (PS)-b-polymethyl methacrylate (PMMA) block copolymers (BCP)) using either ultralow energy cesium or the more recently introduced C60(++) (under NO dosing and with sample cooling) and argon cluster ion beams (using Ar-1500(+) ions at 5 keV). The latter improved the quality of the depth profiles, especially the argon cluster ion beam, as it is characterized by a greater homogeneity for the sputter yields of PS and PMMA. No significant artifacts were observed, and this was confirmed by the comparison of depth profiles obtained from films with variable thickness, annealing time, and morphology (cylindrical blocks vs spherical blocks). Comparison to a theoretical model (hexagonal centered pattern) ensured that the ToF-SIMS depth profiles described the real morphology and may thus be a relevant characterization tool to verify the morphology of the films as a function of the deposition parameter

Cooperative Surface Passivation and Hierarchical Structuring of Zeolite Beta Catalysts

We report a method to prepare core-shell zeolite beta (*BEA) with an aluminous core and an epitaxial Si-rich shell. This method capitalizes on the inherent defects in *BEA crystals to simultaneously passivate acid sites on external surfaces and increase intracrystalline mesoporosity through facile post-hydrothermal synthesis modification in alkaline media. This process creates more hydrophobic materials by reducing silanol defects and enriching the shell in silica via a combination of dealumination and the relocation of silica from the core to the shell during intracrystalline mesopore formation. The catalytic consequences of *BEA core-shells relative to conventional analogues were tested using the biomass conversion of levulinic acid and n-butanol to n-butyl levulinate as a benchmark reaction. Our findings reveal that siliceous shells and intracrystalline mesopores synergistically enhance the performance of *BEA catalysts.This work was supported by BASF Corporation. Additional support for JDR was provided by The Welch Foundation (Award E-1794). ToF-SIMS analysis was carried out with support provided by the National Science Foundation CBET-1626418. This work was conducted in part using resources of the Shared Equipment Authority at Rice University. JGM received funding for this project from the European Union’s Horizon 2020 research and innovation program under grant agreement No 872102. JGM and NL thank the Spanish Ministry of Science and Innovation and AEI/FEDER, UE through the project ref. RTI2018-099504-B-C21. NL acknowledges additional support from the University of Alicante (UATALENTO17-05)

Quantitative analysis of Si/SiGeC superlattices using atom probe tomography

International audienc

Quantitative investigation of SiGeC layers using atom probe tomography

International audienceThe quantification of carbon and germanium in a Si/SiGeC multilayer structure using atom probe tomography has been investigated as a function of analysis conditions. The best conditions for quantitative results are obtained using an intermediate electric field and laser power. Carbon evaporation shows strong spatial and temporal correlation. By using multi-ion event analysis, an evaporation mechanism is put forward to explain the modification of mass spectra as a function of electric field and laser power