Gas Cluster Ion Beam Sputtering Research Articles

From surface to core: Comprehensive ToF-SIMS insights into pharmaceutical tablet analysis

This study presents an innovative approach to pharmaceutical analysis using time-of-flight secondary ion mass spectrometry (ToF-SIMS) to investigate tablets containing paracetamol in the solid state without the need for traditional pretreatment methods (dissolution, filtration, etc.). Employing both MS1 and MS2 ToF-SIMS spectra, signals characteristic of paracetamol and a fragmentation mechanism were assigned. Some findings challenge previous interpretations of certain ToF-SIMS signals attributed to paracetamol, highlighting the need for reevaluation. Moreover, as the sample was used without any pretreatment (a purchased tablet), which has a complex matrix, the resulting ToF-SIMS mass spectra can suffer from spectral interferences. The use of multivariate statistical analysis resulted in the assignment of unique signals for paracetamol. Additionally, ToF-SIMS imaging was utilized with high mass and lateral resolution, employing the delayed-extraction ToF analyzer mode, to image the two-dimensional distribution of species on the tablet’s surface with an emphasis on paracetamol distribution. The use of a gas cluster ion beam (GCIB) sputtering source in association with ToF-SIMS enabled the visualization of the three–dimensional distribution of species within the tablet. This thorough investigation advances knowledge regarding the characterization of paracetamol and offers the examination of pharmaceuticals without sample pretreatment with elemental and molecular-specific information.

Multidimensional Chemical Imaging of Polyolefin Dispersion Can Coatings Using Time-of-Flight Secondary Ion Mass Spectrometry with Gas Cluster Ion Beam Sputtering.

Multidimensional Chemical Imaging of Polyolefin Dispersion Can Coatings Using Time-of-Flight Secondary Ion Mass Spectrometry with Gas Cluster Ion Beam Sputtering.

XPS investigation of monoatomic and cluster argon sputtering of zirconium dioxide

The surfaces of zirconium dioxide and yttria-stabilized zirconia (YSZ) have been analyzed using x-ray photoelectron spectroscopy after ion sputtering with monoatomic Ar+ or an argon gas cluster ion beam (GCIB). The O/Z ratio and new components in the Zr 3d lines show reduction to lower oxidation states when sputtered with monoatomic Ar+, but significantly less damage is observed when GCIB sputtering is used. The damaged surface layer caused by Ar+ sputtering can be removed by subsequent GCIB sputtering. However, the depth resolution observed in depth profiles of thin YSZ films was significantly better when Ar+ sputtering is used. Differences in the Sn content in the oxidized Zr-4 specimen were also observed when comparing Ar+ and GCIB sputtering, suggesting preferential sputtering.

Development of Ar gas cluster ion beam system for surface preparation in angle-resolved photoemission spectroscopy.

Gas cluster ion beam (GCIB) sputtering has a high potential for obtaining clean and flat surfaces on materials without causing structural or compositional damage. We have developed an Ar cluster GCIB system for surface preparation in angle-resolved photoemission spectroscopy (ARPES). The constructed GCIB system is compatible with ultrahigh vacuum and achieves a beam current of 10 µA. We examined the usefulness of our GCIB system for high surface-sensitive ARPES measurements by applying it to several representative materials, e.g., Sb, GaAs, and Te. The results show that the constructed GCIB system is very useful for preparing a clean flat surface on crystals, widening opportunities for precise ARPES measurements for materials whose crystal surfaces or orientations are hardly obtained by a simple cleaving method.

Tandem GCIB-ToF-SIMS and GCIB-XPS analyses of the 2-mercaptobenzothiazole on brass

Surface analysis of 2-mercaptobenzothiazole (MBTH) adsorbed on brass from 3 wt.% NaCl solution was performed by means of X-ray photoelectron spectroscopy and tandem (MS/MS) time-of-flight secondary ion mass spectrometry (ToF-SIMS). These surface analytical techniques were used in association with the gas cluster ion beam (GCIB) sputtering method at various acceleration energies and cluster sizes, which slowly removes the surface layer and leaves the chemical information intact during the sputtering of the very thin surface layer. In addition, MS1 ToF-SIMS was used for 2D and 3D imaging to show the molecular and elemental distribution of the surface species. Using the tandem ToF-SIMS capability, the MS2 spectra clearly confirmed the presence of MBTH on the surface. Moreover, organometallic complexes were indicated, which formed between the MBTH and Cu ions released due to the corrosion of the brass. These analyses were performed based on the fragmentation products identified in the MS2 spectra.

Spectroscopic analysis and in situ adsorption of 2-mercaptobenzothiazole corrosion inhibitor on Zn from a chloride solution

This work describes the surface analytical characterization of 2-mercaptobenzothiazole (MBTH), which is considered to be a corrosion inhibitor for zinc and was adsorbed on the surface from 3 wt% NaCl. First, tandem (MS/MS) time-of-flight secondary ion mass spectrometry (ToF-SIMS) was employed to determine the signal that corresponds to the parent ion MBTH molecule in negative and positive polarities. The properties of the MBTH surface layer were investigated by gas cluster ion beam (GCIB) sputtering associated with X-ray photoelectron spectroscopy (XPS) and ToF-SIMS measurements. The optical functions and thickness of the films forming were determined by the time-resolved in situ spectroscopic ellipsometry, revealing the growth mechanism of the adorbates.

Combining advanced photoelectron spectroscopy approaches to analyse deeply buried GaP(As)/Si(1 0 0) interfaces: Interfacial chemical states and complete band energy diagrams

The epitaxial growth of the polar GaP(100) on the nonpolar Si(100) substrate suffers from inevitable defects at the antiphase domain boundaries (APDs), resulting from mono-atomic steps on the Si(100) surface. Stabilization of Si(100) substrate surfaces with As is a promising technological step enabling the preparation of Si substrates with double atomic steps and reduced density of the APDs. In this paper, 4–50-nm-thick GaP epitaxial films were grown on As-terminated Si(100) substrates with different types of doping, miscuts, and As-surface termination by metalorganic vapor phase epitaxy (MOVPE). The GaP(As)/Si(100) heterostructures were investigated by X-ray photoelectron spectroscopy (XPS) combined with gas cluster ion beam (GCIB) sputtering and by hard X-ray photoelectron spectroscopy (HAXPES). We found residuals of As atoms in the GaP lattice (∼0.2–0.3 at.%) and a localization of As atoms at the GaP(As)/Si(100) interface (∼1 at.%). Deconvolution of core level peaks revealed interface core level shifts. In As core levels, chemical shifts between 0.5 and 0.8 eV were measured and identified by angle-resolved XPS measurements. Similar valence band offset (VBO) values of 0.6 eV were obtained, regardless of the doping type of Si substrate, Si substrate miscut or type of As-terminated Si substrate surface. The band alignment diagram of the GaP(As)/Si(1 0 0) heterostructure was deduced.

Ion distribution in iron oxide, zinc and manganese ferrite nanoparticles studied by XPS combined with argon gas cluster ion beam sputtering

In this work, the influence of X-ray irradiation and two types of surface sputtering methods is thoroughly studied. The first one, monoatomic sputtering, resulted in the reduction of iron oxide to the metallic iron in a short time of sputtering. The second studied technique is argon cluster sputtering, which uses lower energies per atom, hence the modification of the structure of the samples is greatly reduced. Based on the XPS characterization of Fe3O4 single crystal the fitting procedure for the Fe 2p spectra for nanoparticles is established. The preliminary results showed that X-rays combined with cluster sputtering resulted in alteration of the morphology and solidification of the surface of the samples. In the response to the morphology modification, the Spot-by-Spot Cluster Procedure is proposed. It allows to thoroughly characterize the layer-by-layer structure of the nanoparticles, without changing it. The Procedure was used to determine the structure of zinc, manganese and zinc-manganese ferrite nanoparticles. Finally, the results show, that depending on the used dopant, its incorporation and the state of iron are changed.

Combining Advanced Photoelectron Spectroscopy Approaches to Analyse Deeply Buried Gap(As)/Si(100) Interfaces: Interfacial Chemical States and Complete Band Energy Diagrams

The epitaxial growth of the polar GaP(100) on the nonpolar Si(100) substrate suffers from inevitable defects at the antiphase domain boundaries, resulting from mono-atomic steps on the Si(100) surface. Stabilization of Si(100) substrate surfaces with arsenic is a promising technological step enabling the preparation of Si substrates with double atomic steps and reduced density of the APDs. In this paper, 4-50 nm thick GaP epitaxial films were grown on As-terminated Si(100) substrates with different types of doping, miscuts, and As-surface termination by metalorganic vapor phase epitaxy. The GaP(As)/Si(100) heterostructures were investigated by X-ray photoelectron spectroscopy (XPS) combined with gas cluster ion beam (GCIB) sputtering and by hard X-ray photoelectron spectroscopy (HAXPES). We found residuals of arsenic atoms in the GaP lattice (0.2-0.3 at.%) and a localization of As atoms at the GaP(As)/Si(100) interface (1 at.%). Deconvolution of core level peaks revealed interface core level shifts. In As core levels, chemical shifts between 0.5-0.8 eV were measured and identified by angle-resolved XPS measurements. Similar valence band offset (VBO) values of 0.6 eV were obtained, regardless of the doping type of Si substrate, Si substrate miscut or type of As-terminated Si substrate surface. The band alignment diagram of the heterostructure was deduced.

Ar gas cluster ion beam assisted XPS study of LiNbO3 Z cut surface

XPS combined with profiling by Ar2500+ gas cluster ion beam (GCIB) sputtering has been used to obtain new refined data on the polarization and processing-dependent Li/Nb ratio for the surface of a LiNbO3 single crystal. The most suitable GCIB parameters (normal incidence, 10 keV energy) and irradiation dose (less than or equal to 2.7 × 1016 ions/cm2) have been determined and employed to perform high resolution depth profile analysis without cluster ion-induced Li/Nb changes. The Li/Nb profiles obtained for Z cut wafers with positive and negative faces revealed the presence of two distinct regions. The initial 0.3 nm-thick region had a low Li/Nb ratio due to machining and leaching and did not show a dependence on the polarity direction. The next profile region had a constant Li/Nb ratio, which depended on the crystal polarity. The Li/Nb ratio for the Z+ surface of a wafer and a cleaved sample exceeded the values for the Z– surface of a wafer by 1.2 times. This result confirms theoretical predictions of a different stoichiometry for Z+ and Z– terminations and indicates the ability of GCIB to reach the surface condition that is close to the perfect termination.

2-Phenylimidazole Corrosion Inhibitor on Copper: An XPS and ToF-SIMS Surface Analytical Study

This work presents a surface analytical study of the corrosion inhibitor 2-phenylimidazole (2PhI) adsorbed on a Cu surface from 3 wt.% NaCl solution. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to investigate the surface phenomena. Various XPS experiments were performed, i.e., survey- and angle-resolved high-resolution XPS spectra measurements, gas cluster ion beam sputtering in conjunction with XPS measurements, and XPS imaging in conjunction with principal component analysis. These measurements were used to detail the composition of the surface layer at depth. In addition, various ToF-SIMS experiments were performed, such as positive ion ToF-SIMS spectral measurements, ToF-SIMS imaging, and cooling/heating in conjunction with ToF-SIMS measurements. This study shows that organometallic complexes were formed between 2PhI molecules and Cu ions, that the surface layer contained entrapped NaCl, that the surface layer contained some Cu(II) species (but the majority of species were Cu(I)-containing species), that the surface was almost completely covered with a combination of 2PhI molecules and organometallic complex, and that the temperature stability of these species increases when 2PhI is included in the organometallic complex.

Degradation Mechanism of Solution-Processed Organic Light-Emitting Diodes: Sputter Depth-Profile Study

We have studied the origin of degradation in solution-processed organic light-emitting diodes (s-OLEDs) by using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS) depth profiling. Successful mechanical exfoliation of top cathode layers from degraded s-OLEDs and Ar gas cluster ion beam sputtering of remaining organic layer stack enabled us to probe chemical and positional changes at the relevant buried interfaces in the degraded device. Our XPS depth profile data showed that device operation induced migration of PEDOT in PEDOT:PSS layer toward the interface between hole transport layer (HTL) and emissive layer (EML), which lowers the hole injection efficiency and shifts the carrier recombination zone toward the interface. TOF-SIMS depth profile data showed that molecular decomposition occurred only in the EML after the device operation. These results depict a scenario in which migration of PEDOT lowers the hole injection efficiency which in turn shifts the recombination zone toward the mixed interface between HTL and EML, where an accumulation of excitons and hole polarons induces strong exciton-polaron quenching that results in molecular break down and device degradation.

Bevel Structure Based XPS Analysis as a Non-Destructive Chemical Probe for Complex Interfacial Structures of Organic Semiconductors.

The bevel structure of organic multilayers produced by finely controlled Ar gas cluster ion beam sputtering preserves both the molecular distribution and chemical states. Nevertheless, there is still an important question of whether this method can be applicable to organic multilayer structures composed of complex or ambiguous interfaces used in real organic optoelectronic devices. Herein, various bevel structures are fabricated from different types of organic semiconductors using a solution-based deposition technique: complicatedly intermixed electron-donor and electron-acceptor bulk heterojunction structure, thin film structure with an internal donor-acceptor concentration gradient, and multi-layered structure with more than three layers. For these organic material combinations listed above, the bevel structure is fabricated with finely tuned Ar gas cluster ion beam sputtering. The location-dependent X-ray photoelectron spectroscopy (XPS) results obtained for each bevel structure exactly correspond to the XPS depth profiles. This result demonstrates that the bevel structure analysis is a powerful method to distinguish subtle differences in chemical component distributions and chemical states of organic semiconductors even with complex or ambiguous interfaces. Ultimately, due to its reliability as verified by this study, the proposed bevel structure analysis is expected to greatly expand other analytical techniques with a limited spatial or depth resolution.

The Interface Characterization of 2-Mercapto-1-methylimidazole Corrosion Inhibitor on Brass

This work presents a detailed surface analytical study and surface characterization, with an emphasis on the X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses of 2‑mercapto‑1‑methylimidazole (MMI) as a corrosion inhibitor for brass. First, the electrochemical measurements demonstrated a corrosion inhibition effect of MMI in a 3 wt.% NaCl solution. Next, the formation of the MMI surface layer and its properties after 1 month of immersion was analyzed with attenuated total reflectance–Fourier-transform infrared spectroscopy, atomic force microscopy, field-emission scanning electron microscopy, and contact angle analysis. Moreover, to gradually remove the organic surface layer, a gas cluster ion beam (GCIB) sputtering source at different accelerated voltages and cluster sizes was employed. After each sputtering cycle, a high-resolution XPS analysis was performed. Moreover, an angle‑resolved XPS analysis was carried out for the MMI-treated brass sample to analyze the heterogeneous layered structure (the interface of the MMI organic/inorganic brass substrate). The interface properties were also investigated in detail using ToF-SIMS for spectra measurements and 2D imaging. Special attention was devoted to the possible spectral interferences for MMI‑related species. The thermal stability of different MMI-related species using molecular-specific signals without possible spectral interferences was determined by performing a cooling/heating experiment associated with ToF-SIMS measurements. It was shown that these species desorbed from the brass surface in the temperature range of 310–370 °C.

The influence of the amino group in 3-amino-1,2,4-triazole corrosion inhibitor on the interface properties for brass studied by ToF-SIMS.

RationaleThe detailed surface analysis of corrosion inhibitor surface layers by the application of 1,2,4‐triazole (TRI) and 3‐amino‐1,2,4‐triazole (3‐AT) compounds adsorbed from a 3 wt. % NaCl solution on the brass surface was performed by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The results obtained were additionally supported by X‐ray photoelectron spectroscopy (XPS) measurements.MethodsThe description of the corrosion inhibitor surface layers was elaborated by using ToF‐SIMS and molecular‐specific signals. Characteristic molecular‐specific signals were used to perform 2D ToF‐SIMS imaging and cooling/heating experiment associated with ToF‐SIMS measurements. A detailed surface analysis using high‐resolution angle‐resolved XPS and gas cluster ion beam sputtering in combination with XPS measurements was also carried out.ResultsOrganometallic complexes were formed after the corrosion process of brass with the release of Cu and Zn ions that subsequently connect with TRI or 3‐AT. Using ToF‐SIMS, possible spectral interferences of the organometallic species were considered due to the presence of different organometallic compounds composed of the two main Cu and Zn isotopes, that is, 63Cu and 65Cu and 64Zn and 66Zn. Using the molecular‐specific signals, 2D imaging was performed, which showed a different distribution of different species on the brass surface. In addition, a ToF‐SIMS experiment on thermal stability showed that most of the TRI‐ and 3‐AT‐related species desorb from the brass surface at 460 °C and 405 °C, respectively.ConclusionsToF‐SIMS analysis confirmed the formation of Cu/Zn‐ or Cu2‐inhibitor organometallic complexes, whereas the formation of Zn2‐inhibitor organometallic complexes on the brass surface was not confirmed. ToF‐SIMS imaging showed complete coverage of the brass surface with different Cu/Zn‐ or Cu2‐inhibitor organometallic complexes. The high thermal stability of the corrosion inhibitor surface layers was confirmed by ToF‐SIMS.

Method for Molecular Layer Deposition Using Gas Cluster Ion Beam Sputtering with Example Application In Situ Matrix-Enhanced Secondary Ion Mass Spectrometry.

We introduce a technique for the directed transfer of molecules from an adjacent reservoir onto a sample surface inside the vacuum chamber of a ToF-SIMS instrument using gas cluster ion beam (GCIB) sputtering. An example application for in situ matrix-enhanced secondary ion mass spectrometry (ME SIMS) is provided. This protocol has attractive features since most modern SIMS instruments are equipped with a GCIB gun. No solvents are required that would delocalize analytes at the surface, and the transfer of matrix molecules can be interlaced with SIMS depth profiling and 3D imaging sputtering and analysis cycles, which is not possible with conventional ME SIMS strategies. The amount of molecular deposition can be finely tuned, which is important for such a surface sensitive technique as SIMS. To demonstrate the concept, we used 2,5-DHB as a matrix for the enhancement of three drug molecules embedded in a tissue homogenate. By automatic operation of sputter deposition and erosion (cleanup) cycles, depth profiling could be achieved with ME SIMS with good repeatability (<4% RSD). Furthermore, we explored several different matrix compounds, including α-CHCA and aqueous solutions of Brønsted acids (formic acid) and 3-nitrobenzonitrile, a volatile compound known to spontaneously produce ions. The latter two matrix compounds were applied at cryogenic measurement conditions, which extend the range of matrices applicable for ME SIMS. Enhancement ratios range from 2 to 13, depending on the analytes and matrix. The method works in principle, but enhancement ratios for the drug molecules are rather limited at this point. Further study and optimization is needed, and the technique introduced here provides a tool to perform systematic studies of matrix compounds and experimental conditions for their potential for signal enhancement in ME SIMS.

Time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy study of 2-phenylimidazole on brass.

This work presents the first surface analysis investigation of 2-phenylimidazole (PhI) as a corrosion inhibitor for brass in a 3 wt.% NaCl solution using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS). A time-of-flight secondary ion mass spectrometer was used to describe the elemental and molecular specific signals on the brass surface. Gas cluster/monoatomic ion beam depth profiling and two-dimensional (2D) imaging showed the surface properties of the PhI surface layer. In addition, detailed XPS was used to describe the element-specific signals on the brass surface. Furthermore, principal component analysis demonstrated the distribution of the different phases of the surface. Finally, the applicability of PhI in hot corrosion studies was suggested by a thermal stability experiment. TOF-SIMS measurements showed an intense positive-ion TOF-SIMS signal for protonated PhI, i.e. C9 H9 N2 + at m/z 145.07. Moreover, there was an intense negative-ion TOF-SIMS signal for deprotonated PhI, i.e. C9 H7 N2 ¯ at m/z 143.06. Gas cluster ion beam sputtering associated with the analysis of the XPS-excited Cu L3 M4,5 M4,5 revealed a connection between Cu(I) and PhI to form organometallic complexes. The formation of the organometallic complexes with Cu and Zn metal atoms/ions was identified using TOF-SIMS in positive and negative polarity mode: PhI-Cu, PhI-Cu2 , PhI-Zn, and PhI-Zn2 complexes were present on the brass surface. The TOF-SIMS measurements were supported by XPS measurements.

Improvement of the lubrication properties of grease with Mn3O4/graphene (Mn3O4#G) nanocomposite additive

Although grease can effectively lubricate machines, lubrication failure may occur under high speed and heavy load conditions. In this study, Mn3O4/graphene nanocomposites (Mn3O4#G) were synthetized using a hydrothermal method as lubricant additives. The lubrication properties of compound grease with Mn3O4#G nanocomposite additive under heavy contact loads of 600–900 N (3.95–4.59 GPa) were investigated. First, the nanocomposites were dispersed into L-XBCEA 0 lithium grease via successive electromagnetic stirring, ultrasound vibration, and three-roll milling. Compound grease with additives of commercial graphene (Com#G) was also investigated for comparison. Tribological test results revealed that the trace amounts of Mn3O4#G (as low as 0.02 wt%) could reduce the coefficient of friction (COF) of grease significantly. When the concentration of Mn3O4#G was 0.1 wt%, the COF and wear depth were 43.5% and 86.1%, lower than those of pure graphene, respectively. In addition, under the effect of friction, the microstructure of graphene in Mn3O4#G nanocomposites tends to be ordered and normalized. Furthermore, most of the Mn3O4 transformed into Mn2O3 owing to the high temperature generated from friction. Using the Ar gas cluster ion beam sputtering method, the thickness of the tribofilm was estimated to be 25–34 nm. Finally, the improvement of the lubrication properties was attributed to the synergistic effect of the adsorbed tribofilm, i.e., the graphene island effect and the filling effect of Mn3O4#G.

Surface analysis and interface properties of 2-aminobenzimidazole corrosion inhibitor for brass in chloride solution.

This work presents a corrosion study of 2-aminobenzimidazole (ABI) as a corrosion inhibitor for brass in chloride solution. Electrochemical, field emission scanning electron microscopy, atomic force microscopy, and contact angle measurements showed that ABI mitigates brass corrosion after short-, medium-, and long-term immersion periods. Next, a detailed surface analysis of the ABI adsorbed on the brass surface was performed using attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) techniques. XPS imaging was performed in association with principal component analysis to determine the different phases on the surface. In order to describe the in-depth composition of the ABI surface, an angle-resolved XPS analysis was performed. This analysis was further supported by gas cluster ion beam sputtering to gradually remove the ABI surface layer, and XPS analysis was performed after each sputtering cycle. Finally, TOF-SIMS analyses showed the formation of Cu/Cu2-ABI and Zn-ABI compounds, the 2D distribution of ABI-related compounds, and their thermal stability on the brass surface. Graphical abstract.

Development and analysis of frits for enamelling AA2024, AA6082 and AA7075 aluminium alloys

AbstractThis study reports the development of frits with different composition, time, and firing temperature for mitigating the corrosion of AA2024, AA6082, and AA7075 aluminium alloys in chloride‐containing solutions. The melting points of the frits were determined using a heating microscope, while the thermal expansion was measured using dilatometry. Several frits were prepared, of which seven were coated on AA2024, AA6082 and AA7075 aluminium alloys. The corrosion resistance of the coated samples was tested in 5 wt% NaCl solution at 25°C using potentiodynamic curve measurements. The corrosion resistance of the coated samples increased compared with the respective uncoated aluminium alloys. The composition and in‐depth homogeneity of the best‐performing coated samples were confirmed using a gas cluster ion beam sputtering source associated with X‐ray photoelectron spectroscopy analysis. Furthermore, O2+ sputtering was performed in association with time‐of‐flight secondary ion mass spectrometry to describe the three‐dimensional composition of the frits.