Secondary Ion Mass Spectrometry Study Research Articles

Ruthenium as Schottky metal for SiC-based high temperature hydrogen sensors

ABSTRACTSensor response characteristics of Ru/3C-SiC (epitaxial layer of SiC on Si substrates) Schottky junctions were studied at different temperatures (200 – 400 °C) in presence of varying concentrations of hydrogen from 5000 – 20000 ppm. The output signal of the sensor, the response time and the reversibility were investigated from the transient response characteristics of the sensors. The sensor parameters improved with higher operating temperature, up to 400 °C. The sensitivity of the sensors was found to be a function of applied bias across the Schottky junction. As compared with the Pd/3C-SiC junctions, the Ru/3C-SiC Schottky sensors showed higher resolution and better reversibility in the hydrogen concentration range 10000 to 20000 ppm. The SIMS (Secondary Ion Mass Spectrometry), RBS (Rutherford Backscattering Spectrometry) and GIXRD (Glancing Incidence X-ray Diffraction) studies indicated that up to 400 °C there was no formation of ruthenium silicide at the Ru/3C-SiC interface.

A multi-technique surface study of the mercury(II) chalcogenide ion-selective electrode in saline media.

X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), rotating disc electrode-electrochemical impedance spectroscopy (RDE-EIS) and synchrotron radiation-grazing incidence X-ray diffraction (SR-GIXRD) have been used to study the response mechanism of the mercury(II) chalcogenide ion-selective electrode (ISE) in saline media. XPS and SIMS have shown that the chalcogenide surface is poisoned by silver chloride, or a mixture of silver halides, on continuous exposure to synthetic and real seawater. Significantly, the in-situ SR-GIXRD study demonstrated that electrode fouling in synthetic seawater is linked to the formation of poorly crystalline or amorphous silver chloride, and that the low level of free mercury(II) in a calibration buffer (i.e., 10(-14) M) is able to undergo metathesis with silver(II) sulfide in the membrane generating mercury(II) sulfide. Significantly, the results of this detailed surface study have shown that silver chloride fouling of the electrode is ameliorated in real seawater comprising natural organic ligands, and this has been attributed to the peptization of silver chloride by the surfactant-like nature of seawater ligands at pH 8. RDE-EIS aging studies have revealed that the chalcogenide membrane experiences a sluggish charge transfer reaction in seawater, and contrary to a previous report for a static electrode, the seawater matrix does not passivate the RDE. The results of this XPS, SIMS, RDE-EIS and SR-GIXRD study have elucidated the response mechanism of the mercury(II) ISE in saline media.

A Feasible SIMS Study for Characterizing Ferric Oxyhydroxides Formed on the Iron Surface Using Deuterium

Secondary ion mass spectrometry (SIMS) has been applied to hydrogen and deuterium analysis for ferric oxyhydroxides, which is formed by reaction of an iron substrate with water; either H2 Oo r D 2O containing a small amount of sodium chloride. Mass spectra of positive and negative ions obtained by SIMS showed that deuterium in ferric oxyhydroxides can be differentiated from hydrogen, although many species of secondary ion peaks are detected. Mass spectra from an iron sample, which firstly reacted with H2O, subsequently dried and finally reacted with D2O, indicated that D2O reaches a reaction front of the iron substrate through ferric oxyhydroxides formed by reaction with H2O. This implies that the ferric oxyhydroxides formed by reaction with H2O are, more or less, porous and thus water penetrates into ferric oxyhydroxides to the substrate. These results also suggest that SIMS analysis using isotopes enable us to characterize a formation process of ferric oxyhydroxides and permeability of foreign ions in the ferric oxyhydroxides.

Time of flight secondary ion mass spectrometry study of silicon nanoclusters embedded in thin silicon oxide layers

Si nanoclusters have been formed by 5 keV Si+ implantation at a fluence of 1×1016 atoms/cm2 into a 200 Å thin thermally grown SiO2 film on Si (100), followed by thermal treatment at 1000 °C with different annealing times. All the annealed samples show a broad photoluminescence spectrum with increasing intensity as function of annealing time. The use of a dual beam time of flight secondary ion mass spectrometry in negative mode with Cs+ ions at low energy for sputtering allows us to observe variations in Si− signal due to excess of silicon atoms introduced by implantation. With the high sensitivity achieved using this instrumental configuration it is possible to follow Sin− signals which give information about the chemical enviroment of the Si atoms. The possibility of studying the time evolution of the nucleation and growth of nanoclusters has been investigated.

SIMS and RBS study of thermally annealed Pd/β-SiC interfaces

The Pd/β-SiC interfaces were studied using secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectrometry (RBS). This was done with the intent of clarifying any reaction or inter-diffusion at the interface upon prolonged annealing at different temperatures in air. SIMS study indicates that the interface is stable up to 400 °C for at least 12 h. However, at 800 °C, the interface was completely degraded with significant inter-diffusion of palladium and silicon. The RBS study confirms the SIMS observations.

Surface studies of a chalcogenide glass ferric ion‐selective electrode Part 2: The effects of inorganic ions, organic ligands and seawater on sensor response

AbstractX‐ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and electrochemical impedance spectroscopy (EIS) have been used to investigate the effect of inorganic ions, organic ligands and seawater on the response of the FeIII ion‐selective electrode (ISE). X‐ray photoelectron spectroscopy has shown that the formation of antimony(V) oxide/hydroxide on the chalcogenide glass membrane soaked in seawater is dictated by electrode kinetics. It has been found that selenide atoms in the chalcogenide glass are replaced by oxygen in the presence of seawater. Furthermore, EIS aging studies demonstrated that the chalcogenide glass membrane experiences a sluggish charge transfer reaction in seawater. By contrast, SIMS imaging and depth profiling on various regions of a seawater‐exposed membrane identified a phase comprising iron oxide–hydroxide–carbonate–carboxylate. Furthermore, SIMS revealed a uniform chemisorption of oxygen on the membrane surface, and adsorption does not appear to be related to specific coordination sites. X‐ray photoelectron spectroscopy failed to detect any chloride chemisorption on the membrane surface, whereas in situ EIS showed that chloride along with hydroxide ions facilitate the charge transfer process of the FeIII ISE. Moreover, the effect of humic acid on the FeIII ISE was studied using EIS. The results of this XPS, SIMS and EIS study have enabled the derivation of a response mechanism for the FeIII ISE in seawater. Copyright © 2002 John Wiley & Sons, Ltd.

Secondary ion mass spectroscopy study of failure mechanism in organic light emitting devices

Secondary ion mass spectroscopy is used to examine the dark, non-emissive defects on the organic light emitting device. Boundary movements are originated from electrode imperfection. Due to flexibility and movability of polymer layer, distribution variations and a more severe indium and calcium overlapping are detected in dark spot defect area. Boundary movements are not in good agreement between different layers. Interfaces became undulate. The closeness and proximity between the In sharp spikes and cathode metal protrusion leads to the initial point of dark spot. We demonstrate that the presence of cathode imperfection and interface roughness of different layers correlated to the device dark spot formation.

Rare earth element variations resulting from inversion of pigeonite and subsolidus reequilibration in lunar ferroan anorthosites

We present results of a secondary ion mass spectrometry study of the rare earth elements (REEs) in the minerals of two samples of lunar ferroan anorthosite, and the results are applicable to studies of REEs in all igneous rocks, no matter what their planet of origin. Our pyroxene analyses are used to determine solid-solid REE distribution coefficients (D = CREE in low-Ca pyroxene/CREE in augite) in orthopyroxene-augite pairs derived by inversion of pigeonite. Our data and predictions from crystal-chemical considerations indicate that as primary pigeonite inverts to orthopyroxene plus augite and subsolidus reequilibration proceeds, the solid-solid Ds for orthopyroxene-augite pairs progressively decrease for all REEs; the decrease is greatest for the LREEs. The REE pattern of solid-solid Ds for inversion-derived pyroxene pairs is close to a straight line for Sm-Lu and turns upward for REEs lighter than Sm; the shape of this pattern is predicted by the shapes of the REE patterns for the individual minerals.Equilibrium liquids calculated for one sample from the compositions of primary phases, using measured or experimentally determined solid-liquid Ds, have chondrite-normalized REE patterns that are very slightly enriched in LREEs. The plagioclase equilibrium liquid is overall less rich in REEs than pyroxene equilibrium liquids, and the discrepancy probably arises because the calculated plagioclase equilibrium liquid represents a liquid earlier in the fractionation sequence than the pyroxene equilibrium liquids. “Equilibrium” liquids calculated from the compositions of inversion-derived pyroxenes or orthopyroxene derived by reaction of olivine are LREE depleted (in some cases substantially) in comparison with equilibrium liquids calculated from the compositions of primary phases. These discrepancies arise because the inversion-derived and reaction-derived pyroxenes did not crystallize directly from liquid, and the use of solid-liquid Ds is inappropriate. The LREE depletion of the calculated liquids is a relic of formation of these phases from primary LREE-depleted minerals. Thus, if one attempts to calculate the compositions of equilibrium liquids from pyroxene compositions, it is important to establish that the pyroxenes are primary. In addition, our data suggest that experimental studies have underestimated solid-liquid Ds for REEs in pigeonite and that REE contents of liquids calculated using these Ds are overestimates.Our results have implications for Sm-Nd age studies. Our work shows that if pigeonite inversion and/or subsolidus reequilibration between augite and orthopyroxene occurred significantly after crystallization, and if pyroxene separates isolated for Sm-Nd studies do not have the bulk composition of the primary pyroxenes, then the Sm-Nd isochron age and εNd will be in error.

Amorphous selenium thin films prepared using chemical bath deposition: optimization of the deposition process and characterization

Amorphous selenium films were prepared at room temperature using the simple and safe method of chemical bath deposition. This was achieved with an acidified solution of Na2SeSO3 at a pH value of 4.5. In order to confirm the formation of amorphous selenium (a-Se), samples were characterized using x-ray diffraction, x-ray photoelectron spectroscopy, secondary ion mass spectroscopy and optical absorption studies. The optical bandgap of the material was found to be 2.09 eV. Indium selenide could be prepared by annealing this a-Se in a multilayer structure glass/SnO2/a-Se/In.

Optical and Structural Characterization of InGaAs/AlAsSb Quantum Wells Grown by Molecular Beam Epitaxy

We report here a photoluminescence (PL) and secondary ion mass spectrometry (SIMS) study of highly Si-doped InGaAs/AlAsSb quantum wells (QWs) that are lattice-matched to InP substrates grown by molecular beam epitaxy (MBE). It is found that PL line-shape degradation caused by high Si doping of the upper (surface side) AlAsSb barrier can be controlled by inserting an undoped AlAsSb spacer layer. However, when the lower (substrate side) AlAsSb barrier was doped, the broadening of the PL spectra was found to be unavoidable even with a 10 nm spacer layer. SIMS depth profiles confirm the out-diffusion of In and Ga from the InGaAs well to the AlAsSb barriers and Al incorporation into the InGaAs well. This group III species interdiffusion combined with the exchange reaction between As and Sb is confirmed to be the origin of the markedly broad PL spectra.

Tunnel diode collector contact in InP based PNP heterojunction bipolar transistors

A tunnel diode collector contact to InP based PNP heterojunction bipolar transistors (HBTs) is suggested and demonstrated. The additional heavily doped n-type contact layer replaces the thick p-type contact layer required in conventional structures. The thermal and electrical properties of the collector contact layer thus become similar to those of NPN HBTs. A secondary ion mass spectroscopy study explores the maximum tin doping level that can be obtained in the base. Finally, the temperature dependence of the current gain is presented and interpreted.

SIMS STUDY OF THE CALCIUM-DEPRIVATION STEP RELATED TO EPIDERMAL MERISTEM PRODUCTION INDUCED IN FLAX BY COLD SHOCK OR RADIATION FROM A GSM TELEPHONE

Exposing seedlings of the flax, Linum usitatissimum L., to a variety of weak environmental stresses plus a 2-day calcium deprivation triggers the common response of production of epidermal meristems in the hypocotyl. Here, we show that the same response was induced by a 1 min cold shock. Epidermal meristem production was also induced by a single 2-h exposure to radiation emitted at 0.9 GHz at non-thermal levels by a GSM telephone. This flax-based system is therefore well suited to studying the effects of low intensity stimuli, including those of electromagnetic radiation. To begin to determine the underlying mechanisms, in which calcium is implicated, it is desirable to analyse the changes in ions in the tissues affected. We therefore performed a Secondary Ion Mass Spectrometry (SIMS) study of the distribution of the main inorganic cations in the hypocotyl of control and calcium-deprived seedlings. This showed decreases in calcium, sodium and potassium and an increase in magnesium that did not alter substantially the overall ratio of divalent to monovalent cations.

Substrate temperature studies of SrBi2(Ta1−xNbx)2O9 grown by pulsed laser ablation deposition

Ferroelectric SrBi2(Ta1−xNbx)2O9 (SBNT) thin films were deposited on Pt/TiOx/SiO2/Si substrates at various substrate temperatures by the pulsed laser ablation deposition method. X-ray diffraction shows that the film has a fluorite structure at a substrate temperature of 500 °C. The fluorite structure was transformed into perovskite phase at 550 °C and was fully crystallized at temperatures ⩾700 °C, with a secondary phase present. Secondary ion mass spectroscopy and x-ray photoelectron spectroscopy studies reveal that the secondary phase was a nonferroelectric Bi-deficient pyrochlore phase at the SBNT/Pt interface and the film surface. The pyrochlore structure has a detrimental effect on the ferroelectric properties (i.e., the remanent polarization, coercive field, leakage current and fatigue) of the film. The remanent polarization and coercive field for the film grown at a substrate temperature of 700 °C were 4.79 μC/cm2 and 68.68 kV/cm, respectively, with leakage current <10−7 A/cm2 even at an applied voltage of 8 V and 30% degradation in endurance against fatigue after 2×1012 switching cycles.

On the Argon Annealing-Based Improvements of the Properties of Ultra-Thin Oxynitrides Nitrided with NH3

AbstractThermally grown Si3N4 films in NH3 are known to have a higher dielectric constant and a higher N concentration than silicon oxynitrides, although they incorporate hydrogen atoms that induce hot electron carriers during subsequent high temperature processing. Further, a silicon nitride is difficult to grow over about 6 nm thick, due to self-limiting growth. One alternative is SiOxNy post-nitrided with NH3.In this work, we study the scope of improvement of Ar annealed nitrided oxynitrides as a function of annealing temperature and duration. Secondary ion mass spectroscopy (SIMS) studies of the nitrogen and hydrogen profiles suggest increasing N and H removal with increasing annealing time and temperature. Electrical characterizations have been performed to determine the total charge (Qox) and interface trap (Dit) densities at different processing conditions, before and after the annealing step. Post-annealing steps are not found to yield improvements of the electrical properties of these dielectric films. Instead, sometimes Qox is even seen to increase (e.g., after a 30 min Ar anneal at 1000 °C). Therefore, an optimization of such annealing steps is essential in designing nanodielectrics with desired nitrogen amounts and N concentration profiles as well as in understanding related process-structure-function relationships.

SIMS study of silicon oxynitride prepared by oxidation of silicon-rich silicon nitride layer

We proposed a novel process for fabrication silicon oxide–oxynitride–oxide structure for ULSI device applications. By deposition of silicon-rich silicon nitride and then following a thermal oxidation process, a good oxynitride layer was obtained. Secondary ion mass spectroscopy (SIMS) study reveals that the hydrogen content of nitride film at the interface can be reduced by more than 40% when compared to stoichiometric nitride. With this method, high nitrogen content oxynitride and smoother oxynitride/oxide interfaces result in the reduction of the interface charge trapping remarkably.

Studies of cell division (mitosis and cytokinesis) by dynamic secondary ion mass spectrometry ion microscopy: LLC-PK1 epithelial cells as a model for subcellular isotopic imaging.

The feasibility of the renal epithelial LLC-PK1 cell line as a model for cell division studies with secondary ion mass spectrometry (SIMS) was tested. In this cell line, cells undergoing all stages of mitosis and cytokinesis remained firmly attached to the substrate and could be cryogenically prepared. Fractured freeze-dried mitotic cells showed well-preserved organelles as revealed by fluorescence imaging of rhodamine-123 and C6-NBD-ceramide by confocal laser scanning microscopy. Secondary electron microscopy analysis of fractured freeze-dried dividing cells revealed minimal surface topography that does not interfere in isotopic imaging of both positive (39K, 23Na, 24Mg, 40Ca, etc.) and negative (31P, 35Cl, etc.) secondaries with a CAMECA IMS-3f ion microscope. Mitotic cells revealed well-preserved intracellular ionic composition of even the most diffusible ions (total concentrations of 39K+ and 23Na+) as revealed by K : Na ratios of approximately 10. Structurally damaged mitotic cells could be identified by their reduced K : Na ratios and an excessive loading of calcium. Quantitative three-dimensional SIMS analysis was required for studying subcellular calcium distribution in dividing cells. The LLC-PK1 model also allowed SIMS studies of M-phase arrested cells with mitosis-arresting drugs (taxol, monastrol and nocodazole). This study opens new avenues of cell division research related to ion fluxes and chemical composition with SIMS.

A SIMS study on positive and negative ions sputtered from graphite by mass-separated low energy Ne +, N 2+ and N + ions

Temperature effect on positive and negative ion yields sputtered from graphite by low energy Ne +, N 2 + and N + ions was studied using a special mass-separated low energy ion beam system and secondary ion mass spectrometry (SIMS) measurements. The origin of dominant positive and negative ions was discussed according to the obtained temperature effect. It was found that C + ion emission was enhanced by nitrogen ion bombardment compared with Ne + bombardment and decreased to the same level as Ne + bombardment at elevated temperature. The enhancement effect was attributed to adsorption or deposition of nitrogen to form weakly bound C δ+–CN δ− species on the surface. No chemical enhancement effect was observed on C 2 − emission during nitrogen ion bombardment. The C 2 − yield increased with temperature during Ne + and nitrogen ion bombardment and was assigned to originate from carbon network of graphite as a consequence of physical sputtering. During nitrogen ion bombardment, CN − ions dominated both the positive and negative ion emission. CN − ion yield during 800 eV N 2 + and N + bombardment decreased at elevated temperature, whereas during 100 eV N 2 + bombardment, it increased with temperature. CN − yield as a function of kinetic energy of primary ions also exhibited difference from that of C + and C 2 −. Three possible channels for CN − emission have been proposed. At higher primary energy (several hundred eV and above), physical sputtering can partly account for CN − emission. At lower primary energy (below 100 eV), it is attributed to chemical etching of surface carbon atoms by energetic nitrogen atoms and ion-induced desorption of CN species.

Dopant-induced interface disorder in InGaAs/AlAsSb heterostructures lattice matched to InP grown by molecular beam epitaxy

We report here a photoluminescence (PL), high-resolution transmission electron microscopy (HRTEM), and secondary ion mass spectrometry (SIMS) study of highly Si-doped InGaAs/AlAsSb single quantum wells (SQWs) that are lattice-matched to InP substrates grown by molecular beam epitaxy (MBE). High doping is shown to markedly influence the PL spectra of the SQWs. HRTEM shows the bowing and composition grading of the interfaces. SIMS depth profiles confirm the out-diffusion of In and Ga from the InGaAs well to the AlAsSb barriers and Al incorporation into the InGaAs well. These group-III species interdiffusion combined with the exchange reaction between As and Sb are confirmed to be the origin of the extraordinarily broad PL spectra. Modulation doping combined with interface termination is shown to be effective in producing a sharp line-shape in the PL spectra, even for heavily doped SQWs.

Study of inter-diffusion and defect evolution in thin film Al/Ge bilayers using SIMS and positron beam

Depth resolved investigations of defects and their evolution upon inter-diffusion have been carried out on Al/Ge thin film bilayers, using concurrent measurements of positron beam based Doppler broadening lineshape and secondary ion mass spectrometry (SIMS) profiles. Measurements have been made on the as-grown film and films annealed at various temperatures from 370 to 670 K. SIMS studies establish the occurrence of extensive intermixing of the Al and Ge layers beyond 370 K. It is found that there is an asymmetric diffusion across the interface, with Ge being the dominant diffusing species. The intermixed Al/Ge region formed in the near-surface layers of the sample annealed at 670 K shows Ge precipitation, as confirmed by electron microscopy and SIMS imaging. Analysis of the Doppler broadening line shape variation, together with the SIMS concentration profiles, indicates increased production of small vacancy clusters at the Al/Ge interface around 520 K, brought about by the enhanced diffusion of Ge. The interfacial vacancy structure is inferred to be a tri-vacancy cluster.

In Situ Studies of the Nucleation Mechanisms of Tris(cyclopentadienyl)Cerium as Cerium Dopant Source in SrS:Ce Thin Films for Electroluminescent Displays

A systematic evaluation was made of the performance and efficiency of tris(cyclopentadienyl)cerium, Ce(CPD), as potential dopant source in atomic layer epitaxy (ALE) and chemical vapor deposition (CVD) of Ce-doped strontium sulfide (SrS:Ce) for thin-film electroluminescent display applications. In situ growth and characterization studies were carried out, without a vacuum break, of the adsorption and associated dissociation mechanisms of Ce(CPD) within the substrate temperature window typically employed in ALE and CVD SrS:Ce. Associated findings were compared to results from tetrakis(2,2,6,6-tetramethyl-3,5-heptadionato)cerium, which was used as a comparative performance baseline. In this respect, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry studies indicated that, within the typical thermal budget used in ALE and CVD of SrS:Ce films, the Ce(CPD) source decomposed more efficiently than its counterpart, as supported by the observation of reduced hydrocarbon-based surface contamination and a cleaner Ce phase. It was concluded that Ce(CPD) might be a better candidate than for applications as Ce dopant source in ALE and CVD SrS:Ce films. © 2001 The Electrochemical Society. All rights reserved.