SIMS Study Research Articles

An investigation of the Cs bombardment induced altered layer in Si by MEIS, RBS, SIMS and IMPETUS simulation

After O2 ions, Cs is the second most important probe in high-sensitivity SIMS depth profiling analysis due to the achievable high (negative) secondary ion yields. However the depth distribution of Cs is not very well known. We have investigated the buildup of the (internal) Cs concentration profile in Si following 5 keV Cs bombardment at 45° for various fluences ranging from 1014 to 3 × 1016 ions cm2. The implants were carried out in an UHV low-energy implanter after thermal removal of the native oxide layer. Ex-situ RBS analyses were carried out to establish the retained Cs dose as a function of fluence. These showed that saturation conditions are reached after a fluence of 7 × 1015 ions cm2 (areal density 1.7 × 1015at.cm2). The near-surface Cs distribution at saturation was analyzed in-situ by high depth resolution MEIS (< 7 A). 10% of the Cs concentration was found to be segregated within the first 20 A. SIMS studies of the Cs implant at saturation using O2+beams were undertaken after in-situ capping of the implant with a 100–150 A ion beam deposited isotopic 28Si layer, by which depth profile distortion is minimized. Both MEIS and SIMS results show the Cs distribution to extend to beyond 150 A, far in excess of the TRIM predicted projected range. The experimentally obtained profiles have been compared with extensive IMPETUS simulations. Although the FWHM of the experimental and simulated profiles are similar (70 A), the poor agreement on the maximum range of the Cs in Si suggests that a more complex, variable Cs volume model needs to be adopted and/or that additional effects such as segregation and radiation enhanced diffusion need to be incorporated in the model.

Depth resolution in SIMS study of a Fe-Ti multilayer structure

Abstract Depth profiles of Fe-Ti multilayer structure composed of 29 alternate Fe and Ti layers (68 and 84 A thick) were obtained by secondary ion mass spectrometry under 5.5 and 3 keV O2+ bombardment. The effect of oxygen flooding on the in-depth resolution and matrix effects was investigated. Without oxygen flooding during ion bombardment, induced roughness has been developed. With oxygen flooding at 10−5 Torr, the layers are easily visible, the depth resolution is constant with the depth and the Ti signal is representative of the composition profile in the multilayer sandwich (no matrix effects on Ti intensities).

Adsorption states of carbon monoxide on oxygenated Cu(110) faces

Oxygen preadsorption on Cu(110) surfaces strongly reduces the CO desorption peak at 220 K, typical for clean Cu(110) and induces the development of less tightly bound states, which probably correspond to sites on Cu(111) micro-facets, formed in the course of oxygen stimulated surface reconstruction. A smaller part of the CO molecules (⩽ 20%) seems to interact with adsorbed oxygen to give adsorbed CO 2 − which can be stabilized in the presence of CO2 by formation of van der Waals complexes, e.g. [CO2 · CO 2 − ]. At increasing temperature this complex decomposes or disproportionates to give desorbing CO and adsorbed CO 3 − . The interpretation is tentative, but some evidence is given to it by TDS from Cu(111), by XPS, STM and SIMS studies and by theoretical calculations.

Secondary synthesis of gallium-substituted wide-pore zeolites

Isomorphous substitution of Al by Ga into the framework of zeolites Y, ZSM-20, CSY, USY and beta has been achieved by reaction with aqueous gallium fluoride solution. Characterisation by XRD, solid-state NMR, FTIR, SIMS and sorption studies demonstrates that Ga is incorporated into the framework of the zeolite, except for USY where Ga substitutes for non-framework aluminium. Preliminary catalytic results for the conversion of hexane show that reaction rates increase with increased amounts of framework Ga.

TOF SIMS and XPS study of the interaction of hydrolysed γ-aminopropyltriethoxysilane with E-glass surfaces

The interaction of E-glass surfaces with hydrolysed γ-aminopropyltriethoxysilane (HAPS) has been studied by time-of-flight secondary ion mass spectrometry (TOF SIMS) and X-ray photoelectron spectroscopy (XPS). The SIMS spectrum was found to consist of four series of fragmentation patterns, two of which could be assigned to the poly(aminosiloxane). The remaining two series were consistent with the well-known fragmentation of polydimethylsiloxane. Using aqueous extraction procedures, it was possible to show that the largest observable fragment increased in size after treatment with warm water but subsequently decreased again after hot water extraction. This is considered to demonstrate the removal of low molecular weight oligomeric species overlying a crosslinked network of graded density. The positive aluminium ion intensity remained strong, suggesting its incorporation into the silane film. XPS analysis confirmed the incorporation of aluminium ions from the substrate into the coating.

An EELS and static SIMS study of the adsorption and decomposition of propene on Ru(0001)

Electron energy loss spectroscopy (EELS) and static secondary ion mass spectrometry (SSIMS) were used to investigate the adsorption and decomposition of propene on the Ru(0001) single-crystal surface. Propene was found to adsorb at 153 K predominantly in a molecular form, but with some dehydrogenation. Annealing the surface to 203 K produced adsorbed propylidyne species. At 233 K ethylidyne and propylidyne were found to coexist but by 293 K the propylidyne species had decomposed completely to give ethylidyne and some C x H species on the surface.

SIMS studies of hydrogen diffusion through oxides on ZrNb alloy

AbstractHydrogen migration has been followed through the thermally‐grown oxide on a Zr–2.5% Nb alloy. A secondary ion mass spectrometer, calibrated for deuterium, was used to measure the concentration as a function of depth into the film. Thin film oxide specimens, grown in steam to ∼1 μm thickness, were heated to 350 °C and exposed to deuterium gas at pressures ranging from 6 × 10−3 to 6 Pa and times from 30 to 870 min. Some irreversible uptake was detected for all exposures using SIMS. At low exposures, the shape of the deuterium concentration profile is Fickian and diffusion coefficients have been calculated. In this low‐exposure regime, the effect of temperatures between 280 °C and 350 °C on the diffusion equation has been measured. At longer exposures, the rate of deuterium ingress was sharply curtailed and a more complex diffusion profile was observed. Using Raman spectroscopy during a depth profile, the ZrO2 component of the oxide is found to change from a monoclinic–tetragonal mixture at the oxide surface to a primarily tetragonal oxide near the oxide/metal interface. Such changes in phase probably contribute to the complex deuterium diffusion kinetics observed during the longer exposures of the oxide film to deuterium gas.

Surface chemical reactions of Al induced by low-energy D 2+, N 2+, CO +, and CO 2+ ion bombardment

AES and SIMS studies have been carried out on chemical reactions induced by 0.5–4 keV D + 2, N 2 +, CO +, and CO 2 + ion beams on an Al surface. D 2 + impact on Al foils in an ultrahigh vacuum or in a D 2 atmosphere produces secondary ions, AID +,AID 2 + and Al 2D +, in addition to Al + and Al 2 +. These ions are also produced by Ar + impact on Al foils in a D 2 atmosphere. Results obtained on their yields suggest that these D-atom containing secondary ions are produced from aluminium deutendes formed by successive chemical reactions induced by D 2. The Al surface bombarded with N + 2 was covered with A1N completely or partially, depending on the impact energy of N 2 +. The Al surface partially covered with A1N was found to undergo rapid, complete oxidation when exposed to O 2 gas. The results obtained for CO + and CO 2 + impact showed that CO + impact produces Al 4C 3, selectively, while CO 2 + impact produces both Al 4C 3 and aluminium oxide.

Optimization of Zn dopant profiles in a pin-diode/FET by combination of depth profiling techniques: a SIMS, ECV and AES study

Three depth profiling techniques have been combined to optimize the buried p-(Zn)-layer for the monolithic integration of a photodiode (PD) and a field-effect transistor (FET) for optoelectronic application. The Zn diffusion behaviour during MOVPE (metal organic vapour phase epitaxy) growth has been investigated. To meet the requirements of a shallow and a wide Zn profile simultaneously in one substrate a procedure including SiN x masking, selective reactive ion etching (RIE) and substrate etching has been developed. The depth profiling analyses proved to be valuable tools for process optimization.

A SIMS study of nickel deposition on TiO 2(100) : Influence of the stoichiometry of the support

A SIMS study of nickel deposition on TiO 2(100) : Influence of the stoichiometry of the support

Joint nuclear microprobe and SIMS study of microcircuit metallization and passivation layers

Both the nuclear microprobe and secondary ion mass spectrometry have the capability to give information on subsurface metallization and passivation layers, and they have been used at Harwell to study a microcircuit test structure. Results are given which both highlight the complementary nature of these two techniques in this particular case, and illustrate their respective advantages and drawbacks.

XPS and SIMS studies of biodegradable suture materials

AbstractXPS and SIMS have been used to examine the surface composition of copolymers of glycolide (cyclic dimer of glycolic acid) and trimethylene carbonate (TMC) as solvent‐cast films. XPS results on the polymers agree with bulk composition data. SIMS measurements suggest surface enrichment of the TMC component.

ESCA and SIMS studies of plasma treatments of intraocular lenses

AbstractThe surfaces of polymethylmethacrylate (PMMA) intraocular lenses (IOL) modified by treatment in a plasma containing various fluorine‐containing gases were studied by surface analytical techniques. The hydrophobicity imparted to the lens surface was monitored by water contact angle measurements and the degree of fluorination was determined by XPS measurements.The fluorine chemistry on the surface, monitored by XPS and SIMS, was function of the gas mixture employed in the plasma. SIMS imaging was used to monitor coating homogeneity and demonstrated the fragile nature of the coated surface.

SIMS and NRA studies of surface contaminants in gold-rich alloys

Having prepared low melting temperature gold-cadmium alloys by a non-conventional recipe directly from cadmium ores, we expect a possible contamination of the alloys by oxygen, carbon, and sulphur. The non-destructive nuclear (d, p) reaction is used for the quantitative study of these contaminants, while dynamic secondary ion mass spectrometry gives the relative depth profile of these light elements in the alloys.

Influence of thermal treatments on the distribution of contaminating copper near the surface of silicon: a comparative SIMS and XPS study

Quantitative analysis of the concentration profile of copper introduced into silicon by mechanochemical polishing is performed by XPS and SIMS techniques. The evolution of the copper distribution after thermal treatments (450, 750, 900°C) is followed by the same techniques. The results show that an important segregation towards the surface and the near-surface regions occurs during the thermal annealings. Electron-probe X-ray images and SIMS ionic images, as well as the quantitative analysis show that copper is in a precipitated state, sometimes associated with oxygen and carbon.

Interaction of Pd-overlayers with SnO2: comparative XPS, SIMS, and SNMS studies

We report about interaction processes between palladium (Pd) and tin dioxide (SnO2) studied with various surface spectroscopic techniques. Total sputter yields necessary for absolute depth calibration in SIMS are determined for SnO2. Clustering of palladium occurs at low temperatures. Small changes in the XPS relative core level intensities of Pd and Sn allow to determine cluster sizes. Oxidation of Pd in the presence of oxygen at T≥470 K is a prerequisite for diffusion of Pd2+ ions into SnO2 layers. The latter process is confirmed and described quantitatively by evaluating the SIMS and SNMS measurements.

A comprehensive SIMS study of high-T c superconductors

High- T c superconductors YBa 2 Cu 3 O 7− x and ErBa 2 Cu 3 O 7− x as well as their annealed non-superconducting counterparts have been studied by SIMS and complemented by ISS under Ar + ion bombardment. Secondary ion mass spectra and energy distributions of secondary ions of main components and some of the molecular ions have been taken. Peculiarities found in the mass spectra and energy spectra are discussed with regard to the crystalline structure of the compounds. The results obtained suggest a significantly increased binding energy of vttrium and erbium atoms in the lattice of the superconductor. The differences in emission of some ionic species have been found between superconducting and non-superconducting states of the compounds. Two-dimensional and three-dimensional images of the compound have been obtained. The possibility of extracting information on the local compositional inhomogeneity of the superconductor at the background of topographic and chromatic contrasts is discussed. Some effects observed in ion scattering spectra are discussed and compared with SIMS data.

Electrochemical and SIMS studies of cathodically formed hydride layers on titanium

The aims of the present work are to study the influence of the hydride layer (the formation of which during cathodic polarization has been known for quite a long time) on the rate of HER, to explore the applicability of SIMS to detect the presence of hydride and to determine the thickness of such layers. The present measurements show that the formation of hydride suppresses the HER, and that the suppression becomes constant as the hydride layer forms a continuous layer. This is not compatible with the previous literature where the formation of hydride has been reported to stimulate the HER. The present measurements show that the SIMS technique is well suited to detection of absorbed hydrogen in titanium. However, the present effort to use SIMS depth profile measurements to determine the thickness of the hydride layer was unsuccessful. The H − signal shows a smooth decrease from which it is impossible to determine the film thickness. Possible causes for this smooth decrease have been discussed.

SIMS and FAB-MS surface studies of Pt-Sn/Al 2O 3 and Pt 3Pb model catalysts

SIMS and FAB-MS methods have been applied to study surface complexes in chloride containing Pt-Sn/Al 2O 3 and Pt 3Pb in dependence on the temperature of treatment in oxygen. The existence and the limited (700 to ∼850 K) thermal stability of a (PtO x Cl y ) surface complex was confirmed. Pt-Sn/Al 2O 3, air treated (calcined) at 770 K, contains already neighbouring Pt and Sn species being precursors of alloy clusters formed during subsequent reduction.

Nature of active coke in the oxydehydrogenation of ethylbenzene to styrene

The carbonaceous material formed on Al 2 O 3 in the course of the oxydehydrogenation reaction of ethylbenzene to styrene has been considered as the true catalytically active substance. The results of the various analyses made (burn-off experiments; temperature-programmed oxidation, ammonia desorption, ESCA, EPR and SIMS Studies) indicate that the groups containing oxygen in the active coke are quinone/hydroquinone and aroxyl/phenol