Secondary Ion Mass Spectrometry Study Research Articles

An imaging SIMS study on the tribological properties of boron carbide thin films

In this study, boron carbide thin films were deposited on AISI M2 grade high‐speed steel substrates by plasma‐enhanced DC magnetron sputtering of an ‘in‐house’ produced boron carbide target material. Tribological properties of the coatings have been evaluated by a ‘pin‐on‐disc’ tribometer. Wear tracks on boron carbide thin films were investigated by scanning electron microscopy‐energy dispersive spectroscopy, electron probe microanalysis and secondary ion mass spectrometry (SIMS) elemental ion imaging. The results of analyses provided information about the reliability of the SIMS ion imaging compared to the other investigation techniques on nano‐layers and nano‐sized thin films. Copyright © 2012 John Wiley & Sons, Ltd.

SIMS studies of titanium biomaterial hydrogenation after magnetoelectropolishing

Hydrogenation of the commercial purity (99%) CP Titanium Grade 2 biomaterial was investigated using the secondary ion mass spectrometry (SIMS) after two finishing electrochemical operations: standard electropolishing (EP), and magnetoelectropolishing (MEP). The SIMS depth profile analyses were carried out right after electropolishing, and again one month later. The mass spectrograms of secondary positive and negative ions were recorded. SIMS spectra reveal higher emission of positive O+, Ti+ and TiO+ secondary ions which corresponds to higher oxidation of MEP sample. Negative spectra show higher concentration of compounds containing carbon on MEP sample than those of EP sample. Lower content of hydrogen in the near-surface layers in the MEP sample right after the process was revealed. It was found that the concentrations of oxygen and hydrogen alter in time. One month of storage in air causes the contents of hydrogen in EP and MEP samples to be equalized. The SIMS studies performed after a one month period show that the differences in hydrogen contents between EP and MEP samples are not significant.

C60‐ToF SIMS imaging of frozen hydrated HeLa cells

Sample preparation continues to be a major challenge for secondary ion mass spectrometry studies of biological materials. Maintaining the native hydrated state of the material is important for preserving both chemical and spatial information. Here, we discuss a method which combines a sample wash and dry protocol discussed by Berman et al1 (1) followed by plunge freezing in liquid ethane for a frozen-hydrated analysis of mammalian cells (HeLa). This method allows for the removal of the growth media and maintains the hydrated state of the cells so that they can be prepared frozen-hydrated without the need for a freeze-fracture device. The cells, which were grown on silicon, have been successfully re-grown after the cleaning procedure, confirming that a significant portion of the cells remain undamaged during the wash and dry. Results from preliminary SIMS measurements show that is it possible to detect a large variety of bio-molecular signals, including intact lipids from the plasma membrane in the mass range of 700-900 Da from single cells, with little external water interference at the surface.

EMP and SIMS studies on Mn/Ca and Fe/Ca systematics in benthic foraminifera from the Peruvian OMZ: a contribution to the identification of potential redox proxies and the impact of cleaning protocols

Abstract. In this study we present an initial dataset of Mn/Ca and Fe/Ca ratios in tests of benthic foraminifera from the Peruvian oxygen minimum zone (OMZ) determined with SIMS. These results are a contribution to a better understanding of the proxy potential of these elemental ratios for ambient redox conditions. Foraminiferal tests are often contaminated by diagenetic coatings, like Mn rich carbonate- or Fe and Mn rich (oxyhydr)oxide coatings. Thus, it is substantial to assure that the cleaning protocols are efficient or that spots chosen for microanalyses are free of contaminants. Prior to the determination of the element/Ca ratios, the distributions of several elements (Ca, Mn, Fe, Mg, Ba, Al, Si, P and S) in tests of the shallow infaunal species Uvigerina peregrina and Bolivina spissa were mapped with an electron microprobe (EMP). To visualize the effects of cleaning protocols uncleaned and cleaned specimens were compared. The cleaning protocol included an oxidative cleaning step. An Fe rich phase was found on the inner test surface of uncleaned U. peregrina specimens. This phase was also enriched in Al, Si, P and S. A similar Fe rich phase was found at the inner test surface of B. spissa. Specimens of both species treated with oxidative cleaning show the absence of this phase. Neither in B. spissa nor in U. peregrina were any hints found for diagenetic (oxyhydr)oxide or carbonate coatings. Mn/Ca and Fe/Ca ratios of single specimens of B. spissa from different locations have been determined by secondary ion mass spectrometry (SIMS). Bulk analyses using solution ICP-MS of several samples were compared to the SIMS data. The difference between SIMS analyses and ICP-MS bulk analyses from the same sampling sites was 14.0–134.8 μmol mol−1 for the Fe/Ca and 1.68(±0.41) μmol mol−1 for the Mn/Ca ratios. This is in the same order of magnitude as the variability inside single specimens determined with SIMS at these sampling sites (1σ[Mn/Ca] = 0.35–2.07 μmol mol−1; 1σ[Fe/Ca] = 93.9–188.4 μmol mol−1). The Mn/Ca ratios in the calcite were generally relatively low (2.21–9.93 μmol mol−1) but in the same magnitude and proportional to the surrounding pore waters (1.37–6.67 μmol mol−1). However, the Fe/Ca ratios in B. spissa show a negative correlation to the concentrations in the surrounding pore waters. Lowest foraminiferal Fe/Ca ratios (87.0–101.0 μmol mol−1) were found at 465 m water depth, a location with a strong sharp Fe peak in the pore water next to the sediment surface and respectively, high Fe concentrations in the surrounding pore waters. Previous studies found no living specimens of B. spissa at this location. All these facts hint that the analysed specimens already were dead before the Fe flux started and the sampling site just recently turned anoxic due to fluctuations of the lower boundary of the OMZ near the sampling site (465 m water depth). Summarized Mn/Ca and Fe/Ca ratios are potential proxies for redox conditions, if cleaning protocols are carefully applied. The data presented here may be rated as base for the still pending detailed calibration.

SIMS Study of 30keV H<sup>+</sup> Ion-Implanted n-GaAs

A detailed analysis on the depth profiles of 30 keV H+ ion implanted n-GaAs for various doses from 1014 to 1017 cm-2 was carried by using Secondary ion mass spectrometry (SIMS), to identify the buried amorphous layer. The results are correlated with Raman and XRD strain parameter studies. Various thermal parameters are computed for the 30 keV H+ ion implanted n-GaAs and SIMS study reported for the first time.

Microstructures and Magnetism of Silicon co-implanted with Manganese and Carbon ions

Dilute magnetic semiconductors based on transition metal doped silicon have attracted intense interest in recent years due to their compatibility with current silicon technology. Here we present transmission electron microscopy, secondary ion mass spectrometry and ferromagnetic resonance studies of silicon implanted with 1×1016 ions/cm2 of Mn ions and silicon co-implanted with both 1×1016 ions/cm2 of Mn ions and 2×1016 ions/cm2 of carbon ions at a substrate temperature of 350 °C. Afterward, the samples were annealed at temperatures between 800 and 1000°C. The SIMS results show a marked difference between the two specimens while the TEM results show similar features in terms of Mn precipitation and particle evolution. The carbon implanted specimens show additional features that appear to be amorphous silicon pockets within the crystalline implant region. Only one specimen (Mn only implant, unannealed) showed any ferromagnetic properties.

Enhancement of photoluminescence in Er-doped Ag–SiO 2 nanocomposite thin films: A post annealing study

Silver–silica (with Ag 2.8 at.% and 8.7 at.%) nanocomposite (NC) thin films doped with Er +3 (0.1–0.9 at.%) were synthesized by atom beam co-sputtering using 1.5 keV Ar atoms. Optical absorption and photoluminescence (PL) studies of pristine and annealed films were performed, together with Rutherford backscattering and secondary ion mass spectroscopy studies for elemental characterization of the NC films. Optical absorption results of pristine and annealed NC film (with Ag ∼8.7 at.%) confirmed the formation of Ag nanoparticles evidenced by the appearance of characteristic surface plasmon resonance absorption features. Photoluminescence (PL) studies, carried out using Ar Laser pumping at 0.488 μm, the wavelength that the Er ions can absorb resonantly, indicated the presence of PL emission around 1.54 μm in the case of all the as-synthesized samples. The observed PL peak corresponds to the atomic transitions of Er as reported in literature. A relative enhancement in the intensity of PL peak has been observed after annealing the NC films. In the case of NC film with 0.9 at.% Er and 8.7 at.% Ag, the enhancement in PL intensity is almost twice, with respect to the as-deposited sample, for a heat treatment of about 1 h at 600 °C in a nitrogen atmosphere. However for a NC film with Er 0.1 at.% + Ag 2.8 at.%, the PL intensity is enhanced by approximately 3.7 times after annealing at 400 °C for 1 h in nitrogen atmosphere. Since the samples with surface plasmon resonance (SPR) did not show the PL enhancement, the role of SPR in the enhancement of the PL is ruled out. The enhanced PL emission from Er and Ag codoped silica indicates that the Er photo-stimulation is mediated by the energy transfer from Ag nanostructures or ions to Er. Lifetimes of PL peaks for the pristine and annealed samples were also studied. The observed lifetime ∼10 ms is a good indication of excellent PL efficiency.

Role of Titanium Dioxide in Enhancing the Performance of the Alkaline Manganese Dioxide Cathode

In this work the role of TiO2 in improving cathode performance has been investigated through the use of electrode imaging, porosity changes, electrochemical characterisation and changes in the chemical composition of constituent γ-MnO2 particles. Time-of-flight secondary ion mass spectrometry studies revealed that TiO2 is mobile in the electrolyte and associates itself with the porous γ-MnO2 surface. This association gives rise to improved electrode performance by allowing electron/proton pairs to more easily (de)intercalate into the MnO2 structure. Depth profiling confirmed that upon cycling surface TiO2 becomes incorporated into the bulk γ-MnO2 structure inhibiting proton diffusion.

SIMS study on the surface chemistry of stainless steel AISI 304 cylindrical tensile test samples showing hydrogen embrittlement

The local surface chemistry of a low-Ni austenitic stainless steel AISI type 304 used for tensile testing in hydrogen atmosphere is characterized by secondary ion mass spectrometry (SIMS). A chemical map on cylindrical austenitic stainless steel samples can be obtained even after a tensile test. In an effort to obtain the proper chemical element distribution on the samples, the influence of contamination and sample orientation is discussed. An iron oxide on top of a chromium oxide layer is present and Si segregation at grain boundaries is detected. Oxides are judged to reduce the initial hydrogen attack but to be of minor importance for crack propagation during the embrittlement process.

Secondary ion mass spectrometry and X-ray photoelectron spectroscopy studies on TiO 2 and nitrogen doped TiO 2 thin films

Anatase phase TiO 2 and nitrogen (N) doped TiO 2 thin films were synthesized by an ultrasonic spray pyrolysis technique on c-Si (100) substrates in the temperature range 300–550 °C. The former used a precursor solution of titanium oxy acetylacetonate in methanol whereas the later used a titanium oxy acetylacetonate hexamine mixture in methanol. Homogeneity across the film’s thickness and the nature of the film–substrate interface were studied by dynamic depth profiling acquired using secondary ion mass spectrometry SIMS. The stoichiometry and bonding state of various species present in the films were studied using X-ray photoelectron spectroscopy (XPS). N-doping was confirmed by both SIMS and XPS. XPS studies revealed that the nitrogen content of the films synthesized at 300 °C (3.2%) is high compared to that of films made at 350 °C (1.3%).

Nonlinearities in depth profiling nanometer layers

An analysis is made of the sputter depth profiling of ultrathin silicon dioxide layers on silicon to evaluate the variation in the sputtering rate in the first few nanometers. Such changes in sputtering rate are important for the development of the analysis of nanoparticles. Cs+ ions are chosen as an example of a metal ion popular in secondary ion mass spectrometry (SIMS) studies that provide excellent depth resolution. It is found that, if it is assumed that the signal is linear with oxygen content, the sputtering rate falls rapidly by a factor of 4.8, with an exponential decay near 1.2 nm when using 600 eV Cs+ ions at 60° incidence angle. The interface may be described by the integral of the response function of Dowsett et al. developed for SIMS depth profiling of delta layers with λu=0.5 nm, λd=0.7 nm, and σ=0.4 nm, showing the excellent depth resolution. However, if published data for the nonlinearity of the signal with oxygen content are used, the rapid change is still seen but with an initial sputtering rate that is reduced from the above 4.8 to 3.5 times that at equilibrium.

Secondary ion mass spectrometry study of photorefractive-damage-resistant locally Er/Mg-doped near-stoichiometric Ti:Mg:Er:LiNbO3 strip waveguides

Secondary-ion mass spectrometry (SIMS) was used to study the profile characteristics and diffusion properties of Mg, Ti, and Er ions in photorefractive-damage-resistant locally Er/Mg-diffused near-stoichiometric (NS) Ti:Mg:Er:LiNbO3 strip waveguides fabricated on two Z-cut initially congruent, undoped LiNbO3 substrates in sequence by local Er doping at 1100 °C or 1130 °C in air, Mg/Ti pre-diffusion at 1100 °C in wet O2, and post Li-rich vapor transport equilibration (VTE) treatment at 1100 °C. For comparison, a SIMS study was also carried out on the waveguides fabricated without the post-VTE treatment. In order to compensate for the refractive index decrease arising from both the Mg doping and the post-VTE treatment, and hence to get a positive net index increment profile in the Ti-diffused layer, a thicker Ti-film of around 170 nm was coated. Nevertheless, SIMS results show that the Ti diffusion reservoir, as well as the Er and Mg reservoirs, was exhausted. From the SIMS profiles, characteristic diffusion parameters such as the 1/e diffusion width (for Ti only) and depth, diffusivity, and surface concentration of the Mg, Ti, and Er ions are obtained. It is interesting that the Mg distribution in the NS waveguide layer is desirably homogeneous with a concentration [(1.7–2.0) ± 0.3 mol%] higher than the optical damage concentration threshold. The Ti profile follows a sum of two error functions along the lateral direction of NS waveguides with a diffusion width of (12–13) ± 0.5 μm, and a Gaussian function in the depth direction with a 1/e depth of (5.1–6.0) ± 0.2 μm. The Er profile follows also a Gaussian function with a 1/e depth of (3.7–4.4) ± 0.3 μm. In the NS waveguide layer, the mean diffusivity is (7.1 ± 2.2) to (8.3 ± 2.8) μm2/h for Mg, (3.5 ± 0.3) to (4.5 ± 0.4) μm2/h in the lateral direction and (0.54 ± 0.04) to (1.13 ± 0.08) μm2/h in the depth direction for Ti, and (4.1 ± 0.4) to (5.5 ± 0.5) × 10−2 μm2/h for Er. The effects of Li outward diffusion in the initial Er doping procedure, and the Mg codiffusion and post-VTE treatment on the mean Mg, Ti, and Er diffusivities are discussed in comparison with the previously reported results on single Mg, Ti, or Er diffusion and Mg/Ti codiffusion in a pure or homogeneously MgO-doped congruent LiNbO3 crystal. Finally, the keys to the success of the fabrication procedure adopted are discussed.

Postgrown Li-rich vapor transport equilibration-induced Mg diffusion within MgO:LiNbO3 crystal

A number of congruent LiNbO3 crystals homogeneously doped with 5 mol% Mg in growth melt were subjected to Li-rich vapor transport equilibration (VTE) treatments at 1100 °C for different durations. Secondary ion mass spectrometry study shows that the VTE induces the Mg diffusion within the crystal and an inhomogeneous Mg depth profile. The surface Mg concentration, determined from measured ordinary refractive index, shows a strong VTE duration dependence. Neutron activation analysis shows that the amount of MgO diffusing out of the crystal is ignorable, allowing to conclude that the Mg ions counter diffuse to the crystal surface at the early stage of VTE and then come back toward equilibrium as the Li concentration comes to equilibrium. The VTE-induced Li2O content increase in crystal was determined by the gravimetric method. The crystalline phase, crystal composition, and site occupation of Mg and Li are discussed.

SIMS study of annealing effect on element distribution in free-standing Al/Si and Zr/ZrSi2 multilayer films

The results of secondary ion mass spectrometry (SIMS) depth profile analysis of free-standing Al/Si and Zr/ZrSi2 multilayer films by a TOF.SIMS-5 instrument are reported for the first time. A prestudy of elemental composition in Zr and ZrSi2 single layers and Zr/ZrSi2 multilayer films deposited on Si substrates with sublayers revealed enhanced diffusion of carbon in Zr layers. Ion sputtering and charge neutralization conditions were determined to provide fixed position of free-standing thin films during analysis. An elemental composition of 100-nm-thick Zr/ZrSi2 multilayer structures with Mo and B4C protective layers was measured prior and after laser annealing.

Near-stoichiometric Ti:LiNbO3 strip waveguide with varied substrate refractive index in waveguide layer

We report the near-stoichiometric Ti:LiNbO3 strip waveguides fabricated by vapour transport equilibration (VTE) at 1060 °C for 12 h and co-diffusion of 4–8 μm wide, 115-nm thick Ti-strips. Optical studies show that these waveguides are monomode at 1.5 μm and have losses of 1.3 and 1.1 dB/cm for the TM and TE modes, respectively. In the waveguide width/depth direction, the mode field follows a Gauss/Hermite–Gauss profile. A secondary ion mass spectrometry study reveals that the Ti profile follows a sum of two error functions along the width direction and a complementary error function in the depth direction. Micro-Raman analysis shows that the Li-composition in the depth direction also follows a complementary error function. The mean Li/Nb ratio in the waveguide layer is about 0.98. The inhomogeneous Li-composition profile results in a varied substrate index in the guiding layer, and the refractive index profile in the guiding layer is given.

Time-of-flight secondary ion mass spectrometry study on the distribution of alendronate sodium in drug-loaded ultra-high molecular weight polyethylene

The aim of this study was to investigate the drug distribution in ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN), which was developed to treat particle-induced osteolysis after artificial joint replacements, since the drug distribution in UHMWPE could play a key role in controlling drug release. A mixture of UHMWPE powder and ALN was dried and hot pressed to prepare UHMWPE loaded with ALN (UHMWPE–ALN). Fourier transform infrared spectroscopy analysis demonstrated that the hot press had no effect on the functional groups of ALN in UHMWPE–ALN. X-ray diffraction indicated that there was no phase change of the UHMWPE after hot pressing. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra revealed the existence of characteristic elements and functional groups from ALN in UHMWPE–ALN, such as Na+, C3H8N+, PO−3 and PO3H−. In addition, SIMS images suggested that ALN did not agglomerate in UHMWPE–ALN. A small punch test and hardness test were carried out and the results indicated that ALN did not affect the mechanical properties at the present content level. The present study demonstrated that it was feasible to fabricate the un-agglomerated distributed drug in UHMWPE with good mechanical properties. This ALN loaded UHMWPE would have potential application in clinics.

Time of flight secondary ion mass spectroscopy studies of poly(allyl methacrylate-g-dimethylsiloxane) copolymers using cryogenic sample handling techniques: Effects of hydration on surface chemical structure and surface chain length distribution

A series of amphiphilic graft copolymers having a poly(allyl methacrylate) [poly(AMA)] backbone and polydimethylsiloxane (PDMS) side chains were studied by time of flight secondary ion mass spectroscopy (ToF-SIMS) in both hydrated and dehydrated states using cryogenic sample handling methods. Both the copolymers and the PDMS macromers used for grafting to the acrylate backone were synthesized using anionic methods, yielding copolymers with a tightly controlled molecular weight distribution and a tightly controlled PDMS graft chain length in a polymer brush surface configuration. The effects of hydration on surface chemical structure and graft length distribution at the surface were examined. Low mass ToF-SIMS studies provided direct structural evidence that the polymer surface reorganized between hydrated and dehydrated states. High mass ToF-SIMS (1000–5000Da) studies detected oligomeric ion distributions of the PDMS macromer graft at both air and water exposed interfaces, but with a greatly decreased ion yield at the water exposed interface. This marks the first time that detection of high mass oligomeric ion distributions from water exposed (frozen) interfaces has been reported. The chain length distribution of PDMS at the surface was determined and no statistical difference in surface graft length distribution was detected between hydrated and dehydrated copolymers. The effects of polymer bulk structure and composition on graft length distribution at the surface were also examined. High mass ToF-SIMS (1000–5000Da) results indicated that shorter chain lengths were more prominently represented in distribution of graft chains at the surface, regardless of polymer bulk structure, composition, or hydration condition. This is the first report of quantitative and high mass ToF-SIMS study of the effect of water absorption on polymer surface structure in both hydrated and dehydrated states, with control of the polymer structure and composition.

Effect of rapid thermal annealing on the electrical and structural properties of Ru/n‐InP (100) Schottky rectifiers

AbstractThe effects of rapid thermal annealing on the electrical and structural properties of Ru/n‐InP Schottky diode have been investigated by current–voltage (I–V), capacitance–voltage (C–V), X‐ray diffraction (XRD) and secondary ion‐mass spectroscopy (SIMS) techniques. Results showed that the Schottky barrier height of the as‐deposited Ru/n‐InP has been found to be 0.53 eV (I–V) and 0.69 eV (C–V). The Schottky barrier height increased to 0.54 eV (I–V) 0.73 eV (C–V), 0.56 eV (I–V) and 0.78 eV (C–V) after annealing at 300 and 400 °C for 1 min in nitrogen ambient. Further increase in the annealing temperature up to 500 °C resulted in the increase of barrier height to 0.57 eV (I–V) and 0.80 eV (C–V). However, after annealing at temperature 600 °C, the barrier height decreases to 0.51 eV (I–V) and 0.67 eV (C–V). Based on the results of XRD and SIMS studies, the formation of indium phases at Ru/n‐InP interface could be the reason for the increase of barrier height upon annealing at 500 °C. The atomic force microscopy results showed that the surface morphology of the contact annealed at 600 °C is fairly smooth with a root mean square roughness of 1.8 nm.

Secondary ion mass spectrometry study of Ti4+diffusion properties in congruent Er:LiNbO3codoped with moderate concentration of MgO

At 1100 °C, the diffusion properties of Ti4+into congruent LiNbO3crystals codoped with 0.5 mol% Er2O3and different MgO concentrations of 0.5, 1.0, and 1.5 mol% have been studied by secondary ion mass spectrometry (SIMS). ThreeY-cut and threeZ-cut plates with different Mg doping levels were coated with a 60-nm-thick Ti film at first and then annealed at 1100 °C for 28 h in a wet O2atmosphere. SIMS was used to analyze depth profile characteristics of diffused Ti ions and the constituent elements of the substrate as well. The results show that the diffusion reservoir was exhausted and the Ti metal film was completely diffused. All measured Ti profiles follow a Gaussian function. No Mg out-diffusion accompanied the Ti in-diffusion procedure for all crystals studied. The 1/ediffusion depth is similar to 8.3/10.2, 7.4/8.7, and 6.6/8.2 ± 0.2/0.2 μm/μm for theY/Z-cut crystal with the Mg doping level of 0.5, 1.0, and 1.5 mol%, respectively, yielding a Ti4+diffusivity of 0.62/0.93, 0.49/0.67, and 0.39/0.60 ± 0.03/0.03 (μm2/h)/(μm2/h), respectively. The diffusion shows definite anisotropy and a considerable MgO doping level effect. Under the same Mg doping level, the diffusion in aZ-cut crystal is faster. The diffusivity decreases with the increase of the Mg doping level. This effect is qualitatively explained from the viewpoint of the Mg doping effect on concentration of the intrinsic defects in LiNbO3crystal.

Comparison of implantation and diffusion behavior of Ti, Sb and N in ion-implanted single crystal and polycrystalline ZnO: A SIMS study

Implantation and diffusion behavior of Sb, Ti and N in ZnO single crystal and sputter deposited thin films were studied through secondary ion mass spectrometric studies on ion-implanted and thermally annealed samples. Sb was implanted and Ti and N were co-implanted into ZnO single crystals and polycrystalline thin films on Si substrates at room temperature. The implanted samples were then annealed at 800 °C. Depth profiles of implant distributions before and after annealing were examined by Secondary Ion Mass Spectrometry (SIMS). As expected, implant range is sensitive to the mass of the dopants; and the dopant distribution is broadened as implanted elements migrate deeper into the film on thermal annealing. While diffusion of N in the ZnO thin film is not significant, Ti tends to diffuse deeper into the sample during annealing. For Ti and N co-implanted single crystal, annealing induced diffusion causes more redistribution of the lighter N than Ti. In general, implanted dopants diffuse more easily in thin films compared to the single crystal due to the presence of grain boundaries in the latter.