Sputtering of Oxides from LaNi5 Surface
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The changes in chemical composition of the intermetallic alloy LaNi5 surface monolayers were studied using secondary ion mass spectrometry (SIMS) in the process of the alloy interaction with oxygen. The investigated samples were pellets made by pressing the fine-grained LaNi5 alloy. Ar+ ions having energies of 10-18 keV were used as primary ions. The primary beam current density was 9-17 μA·cm-2, which corresponds to the dynamic SIMS mode. The emission intensities of secondary ions were measured within the dynamic range of at least 6 orders of magnitude. Before the measurements, the samples were annealed in residual vacuum at a temperature of ~ 1000 K. After the annealing, the sample surface was cleaned using the primary ion beam until the mass-spectrum composition and secondary ion emission intensity stabilized completely. The gas phase composition was monitored using a gas mass spectrometer. The conducted studies showed that a complex chemical structure including oxygen, lanthanum, and nickel is formed on the surface and in the near-surface region of LaNi5 as a result of its exposure to oxygen. Oxygen forms strong chemical bonds in such a structure with both components of the alloy. This is evidenced by the presence of a large set of oxygen containing emissions of positive and negative secondary ions with lanthanum, with nickel, and oxygen containing lanthanum-nickel cluster secondary ions in mass spectra. The resulting oxide compounds have a bulk structure and occupy dozens of monolayers. In such a bulk oxide structure, the outer monolayers are characterized by the highest ratio of oxygen atom number to the number of matrix atoms. This ratio decreases along the transition from the surface to the underlying monolayers. This process occurs uniformly, without any phase transformation. The observed secondary ions are not a product of association between sputtered surface fragments and oxygen in the gas phase at the fly-off stage after sputter-ejection, but they are products of the oxide compounds being sputtered, hence they characterize the composition of surface and near-surface region.Keywords:
Lanthanum
Secondary Ion Mass Spectrometry (SIMS) extracts chemical, elemental, or isotopic information about a localized area of a solid target by performing mass spectrometry on secondary ions sputtered from its surface by the impact of a beam of charged particles. This primary beam sputters ionized atoms and small molecules (as well as many neutral particles) from the upper few nanometers of the sample surface. The physical basis of SIMS has been applied to a large range of applications utilizing instruments optimized with different types of mass analyzer, either dynamic SIMS with a double focusing mass spectrometer or static SIMS with a Time of Flight (TOF) analyzer. Here, we present a short review of the principles and major applications of three different SIMS instruments located in Switzerland.
Nanometre
Hybrid mass spectrometer
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Matrix (chemical analysis)
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Partial table of contents: PLENARY LECTURES Biosurfaces: A Communications Link Between Solids and Cells (B. Ratner) INVITED LECTURES Cluster Emission in Sputtering (A. Wucher & M. Wahl) IMAGING Analysis of an LCD Device by SIMS (T. Yamamoto, et al.) SPUTTERING AND ION FORMATION Competitive Oxygen Enhancement (E. Brown & P. Williams) DATA PROCESSING SIMS - On the Internet (R. Lareau, et al.) DEPTH PROFILING Depth Resolution Parameters and Separability (M. Dowsett) SURFACE ANALYSIS The Characterization of Fluorolubricants on 8mm Video Tape by TOF-SIMS (T. Hoshi & M. Tozu) SEMICONDUCTORS/MICROELECTRONICS Altered Layer Formation in SiGe (W. De Coster, et al.) MOLECULAR OVERLAYERS Combined SXM/SIMS Investigation of Damage Effects in Molecular Overlayers (G. Becker, et al.) QUANTIFICATION Statistical Process Control (SPC) for SIMS (R. Hockett, et al.) ORGANIC MATERIAL/POLYMERS TOF-SIMS Analysis of a Bio-Polymer (F. Lang, et al.) POSTIONIZATION Quantification of B and As Depth Profiles with Resonant Post-Ionisation Mass Spectrometry (P. De Bisschop, et al.) LIFE SCIENCES Determination of Cyclosporine Metabolites by TOF-SIMS (K. Meyer, et al.) MATERIAL SCIENCES SIMS Analysis of Nitrided Iron and Steel (T. Wu, et al.) MISCELLANEOUS Detection of Mineral Collectors by TOF-LIMS (S. Chryssoulis, et al.) COMBINED TECHNIQUES Quantification and Standardization of LIMS Analysis of Mineral Surfaces (S. Dimov & S. Chryssoulis) MOLECULAR SIMS: ION FORMATION Images of Biologic Tissue Beyond the Static SIMS Limit (P. Todd, et al.) MOLECULAR SIMS: APPLICATIONS Imaging of Langmuir Blodgett Layers by TOF-SIMS (H. Rulle, et al.) INSTRUMENTATION A New Setup for Accelerator-SIMS (R. Ender, et al.).
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Abstract Many important processes, such as corrosion, catalysis, adhesion, and biocompatibility, depend on the composition of the surface or interfacial region. The focus of this article is surface applications of secondary ion mass spectrometry ( SIMS ). In SIMS, a sample is introduced into an ultrahigh vacuum ( UHV ) chamber and bombarded by a primary ion beam. The impact of the primary ion results in the desorption (sputtering) of neutral species, electrons, and secondary ions from the surface of the sample. The secondary ions are mass‐analyzed. SIMS experiments are typically carried out in either a dynamic or a static mode. Historically, the two modes were distinguished on the basis of the primary ion dose ( PID ). Dynamic SIMS uses high PIDs and is generally used for elemental depth‐profiling. Static SIMS uses low PIDs (≤1 × 10 12 ions cm −2 ) and is generally used for the molecular characterization of surfaces; however, the introduction of primary ion cluster sources is extending the static SIMS limit. The advantages of SIMS include high sensitivity, the ability to obtain molecular information, isotopic analysis, imaging, and the analysis of low‐atomic‐number elements such as H and Li.
Polyatomic ion
Characterization
Secondary electrons
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Fast atom bombardment
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Fast atom bombardment
Polyatomic ion
Particle (ecology)
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Auger electron spectroscopy
Electron spectroscopy
Secondary electrons
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High mass resolution time‐of‐flight secondary ion mass spectrometry. Application to peak assignments
Abstract The negative time‐of‐flight secondary ion mass spectrometry spectrum of a trimethylsilylated silicon oxide surface and positive ion spectra of polymethylmethacrylate (PMMA) surfaces before and after treatment with an oxygen plasma are presented. The spectra were recorded with a SIMS spectrometer equipped with a Reflectron‐type mass analyser. This instrument exhibits a mass resolution high enough to be able to determine the chemical composition of the secondary ions directly from the spectra and to resolve peaks of oxygen and non‐oxygen‐containing ions with mass differences of about 0.030 amu at masses well above 200 amu. This information on the chemical composition makes it possible to determine structures of the ions originating from the surfaces, which increases insight into secondary ion formation processes. On the basis of the results from the plasma‐treated PMMA surface, a tentative mechanism is given for the interaction of an oxygen plasma with PMMA in which formation of new polymer chain‐ends containing acetyl groups plays an important role.
Reflectron
Time-of-Flight
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