SIMS Analysis Research Articles

Effect of surface finishing on the oxidation behaviour of a ferritic stainless steel

The corrosion behaviour and the oxidation mechanism of a ferritic stainless steel, K41X (AISI 441), were evaluated at 800°C in water vapour hydrogen enriched atmosphere. Mirror polished samples were compared to as-rolled K41X material. Two different oxidation behaviours were observed depending on the surface finishing: a protective double (Cr,Mn)3O4/Cr2O3 scale formed on the polished samples whereas external Fe3O4 and (Cr,Fe)2O3 oxides grew on the raw steel. Moreover, isotopic marker experiments combined with SIMS analyses revealed different growth mechanisms. The influence of surface finishing on the corrosion products and growth mechanisms was apprehended by means of X-ray photoelectron spectroscopy (XPS) and residual stress analyses using XRD at the sample surfaces before ageing.

Front and back side SIMS analysis of boron-doped delta-layer in diamond

Nowadays the availability of very thin diamond layers in the range of nanometers as well as the possibility to characterize such delta-layer structures are required for the field of photonics and spintronics, but also for the development of next generation high power devices involving boron doping. The fabrication of diamond structures with abrupt interfaces such as superlattices and quantum wells has been recently improved. A very accurate characterization is then essential even though the analysis of such structures is arduous and challenging. SIMS analyses are commonly used to obtain depth profiles of dopants. However, below 10nm in thickness, SIMS induced ion mixing effects which are no longer negligible. Then the raw SIMS profile might differ from the real dopant profile. In this study, we have analyzed a diamond structure containing a thin boron epilayer, especially synthesized to achieve SIMS analysis on both sides and to overcome the effects of ion mixing. We evidence the ion mixing induced by primary ions. Such a structure is a delta diamond layer, comparable to classical boron-doped delta-layer in silicon. Our results show that the growth of boron-doped delta-layer in diamond is now well controlled in terms of thickness and interfaces.

Sulfur isotope signatures in the lower crust: A SIMS study on S-rich scapolite of granulites

Scapolite is an important reservoir for volatiles in the deep crust and provides unique insights into the S isotope signatures at the mantle/crust interface. Here we document the first scapolite reference material (herein referred to as CB1) for in situ S isotope analysis. The chemical and isotopic composition of this euhedral, S-rich scapolite megacryst was characterized via LA-ICP-MS, EPMA, SIMS, and bulk fluorination gas source isotope ratio mass spectrometry. The CB1 scapolite is isotopically homogeneous and our results show that crystal orientation does not affect in situ S isotope SIMS analysis. This makes CB1 an ideal primary calibration standard for in situ analysis of S isotope ratios (36S/32S, 34S/32S and 33S/32S) in scapolite. With this reference material in hand, we then applied in situ SIMS analysis of S isotopes for the first time on scapolite in granulite samples from the lower crust/upper mantle. The analysed sample suite comprises rocks from classic granulite xenolith locations in southeastern Australia, as well as a sample from the high-grade suture zone of the Dahomeyides in south-eastern Ghana. The results show that scapolites in the lower crust have δ34S values between ~−0.5 and +4 (‰ VCDT). These values fall within the range of S isotope signatures present in mantle rocks and provide no evidence for the recycling of seawater-derived S into the lower crust. We propose that scapolite formed during granulite facies metamorphism of igneous cumulates, where S was sourced from precursor igneous sulfides. Sulfur isotope heterogeneities between individual scapolite grains in some of the studied samples may reflect non-uniform S-isotope compositions of igneous S-phases, which precipitated from mantle-derived melt.

MBE growth and doping of AlGaP

In this work, we investigate the impact of growth parameters on surface morphology, doping levels and dopant activation in AlGaP epilayers grown on GaP substrate by solid source molecular beam epitaxy. Atomic Force Microscopy analysis reveals that a smooth surface can be obtained only in the [580–680]°C growth temperature range for a sufficiently large V/III ratio. From C(V), Hall measurements and SIMS analysis, it is shown that a reasonable activated p-doping (Be) value (typically 1018cm−3) can be reached if the growth temperature remains larger than 580°C. For the n-doping (Si), the situation is much more critical, as a growth temperature below 650°C leads to a strongly insulating layer. This dopant activation issue is related to the appearance of deep traps that are generated when growth temperature is not high enough, as evidenced by deep level transient spectroscopy and isothermal deep level transient spectroscopy. It is therefore suggested that electrically-driven devices using AlGaP epilayers have to be carefully designed in order to match both roughness and dopants activation constraints on growth temperatures and growth rates.

The Effect of Implanted Al and/or Y on the Scale Formation on Low-Al Fe20Cr2Al Alloy

The very early stages of the oxidation of an Fe20Cr2Al alloy, unmodified and ion-implanted by aluminium, yttrium and a combination of both elements, Al and Y, were studied at 1100 °C in oxygen using two-stage-oxidation exposures with 18O2 as a tracer and subsequent characterisation of the scales using SIMS analyses of distribution of oxygen isotopes and oxide-related negative ion clusters, SEM observations of the surface morphology and photoluminescence spectroscopy analysis of the phase composition. The scales formed in all cases, except for the Al-implanted alloy, exhibited layered structures, with the outer part comprising Fe- and Cr-rich oxide, and the inner part being Al2O3, which grew due to a mixed outward–inward mechanism . The alumina sub-layers contained the transient oxides and α-Al2O3. Implanted Al significantly affected the mechanism of the scale growth, providing that the scale consisted essentially of α-Al2O3, and grew via a mixed inward-outward mechanism typical for scales on alumina formers.

Primary multiple sulfur isotopic compositions of pyrite in 2.7 Ga shales from the Joy Lake sequence (Superior Province) show felsic volcanic array-like signature

Multiple sulfur isotopes provide a powerful tool to study photochemical and biological processes controlling the Archean sulfur cycle and infer related atmospheric and marine environments. However, our understanding of early Earth’s environment remains limited by the availability of well-preserved geological samples, as most Archean sedimentary rocks have experienced some degree of metamorphic alteration. To evaluate sulfur isotopic behavior during post-depositional processes and elucidate the sulfur cycle at 2.7Ga, we use high-resolution in situ analytical techniques (EPMA and SIMS) to determine elemental compositions and multiple sulfur isotopic compositions of large diagenetic pyrite nodules and fine-grained secondary pyrite disseminated in quartz veins (formed during a lower greenschist metamorphic event) in shales from the 2.7Ga Joy Lake sequence in the southwest Superior Province. Results show that trace metals and sulfur in the secondary pyrite were derived from both metamorphic fluid and pre-existing diagenetic pyrite. Diagenetic pyrite nodules could have been partially dissolved by metamorphic fluid. But the surviving nodules show elemental and isotopic features different from those of the deduced metamorphic fluid endmember, suggesting the nodules were not geochemically altered by metamorphism, and thus preserve primary isotopic signatures acquired during diagenesis. The sulfur isotopic ratios of pyrite nodules show strong variations, with decreasing δ34S values and increasing Δ33S values from cores to rims. This negative Δ33S–δ34S relationship is different from the commonly observed ‘Archean reference line’ defined by most Archean pyrite data, but similar to the ‘felsic volcanic array’. Our observation provides a first possible case from 2.7Ga, the age of peak crustal growth in the Archean, to support the hypothesis that photochemical pathways could be different under conditions of intense volcanic emission. This study also shows that high-resolution SIMS and EPMA analyses are a robust method for distinguishing primary geochemical signatures from post-depositional alteration, and thus may be used to evaluate the sulfur cycle in Archean sedimentary rocks with low-grade metamorphic overprints.

Studies on Activation of High-Mobility III-V Group Semiconductor Materials by Using Microwave Annealing

As semiconductors devices scale down, silicon transistors would reach its limitation below 10 nm. Researching for the novel materials, which could replace silicon, is important. In this study, the new potential materials III-V Group compound semiconductors which are ion implanted with low energy and low dose. In order to keep the ultra-shallow junction and get the best activation, the new annealing technology ─ microwave annealing (MWA) is employed. Microwave annealing is a processing with low energy and longer period. In contrast to the conventional high thermal annealing methods such as rapid thermal annealing (RTA), it is a process with high temperature and ultra-short time. However, the high temperature could cause the dopants diffusion and the ultra-short time might make the destroyed lattices repaired not completely. Ion implant with silicon at different temperature (80°C, and 150°C) into In0.47Ga0.53As(300 nm)/InP substrate, and annealed by low-energy MWA and traditional RTA, respectively to research SPER and electrical activation. By using Raman spectrum, we discover that using MWA energy 2.5P(1.5kW) for 100 s could make the III-V materials achieve SPER by repairing fully. From TEM images, the amorphous layer caused by ion implantation could be recovered to crystal lattices during implantation temperature at 150°C. After annealing by MWA 2.5P(1.5kW) for 100 s, the defects of stacking faults are repaired completely to attain SPER, and it can correspond the Raman results. By using SIMS analysis, it can demonstrate that MWA has better ability to control dopants diffusion. Finally, by using Photoluminescence spectroscopy analysis, the MWA energy 3P(1.8kW) for 100 s could just make silicon dopants get activation. After annealing by MWA 3.5P(2.1kW) for 100 s of implantation at 150°C has the best activation that it has the highest peak.

Multiphase Calcite Cementation and Fluids Evolution of a Deeply Buried Carbonate Reservoir in the Upper Ordovician Lianglitag Formation, Tahe Oilfield, Tarim Basin, NW China

Oil and gas have been found in the Upper Ordovician Lianglitag Formation carbonates in the Tahe Oilfield, Tarim Basin, NW China. This study documents the origin of diagenetic fluids by using a combination of petrology, SIMS, fluid inclusion, and radiogenic isotope analysis. Six stages of calcite cements were revealed. C1-C2 formed in marine to early burial environments. C3 has relatively low δ18OVPDB values (−8.45‰ to −6.50‰) and likely has a meteoric origin. Meteoric water probably fluxed into aquifers during the Early Paleozoic and Late Paleozoic uplift. C4 has δ18OVPDB values typically 3‰ higher than those of C3, and probably formed during shallow burial. C5 displays relatively negative δ18OVPDB values (−8.26‰ to −5.12‰), and the moderate-to-high fluid-inclusion temperatures imply that it precipitated in burial environments. C6 shows homogenization temperatures (up to 200°C) higher than the maximum burial and much lower salinities (<10.61 wt% NaCl), which may suggest that the fluid was deeply recycled meteoric water. The average 87Sr/86Sr ratios of fracture- and vug-filling calcite cements are much higher, indicative of incorporation of radiogenic Sr. Caves and fractures constitute the dominant reservoir spaces. A corresponding diagenesis-related reservoir evolution model was established that favors exploration and prediction.

Predicting instrumental mass fractionation (IMF) of stable isotope SIMS analyses by response surface methodology (RSM)

Instrumental mass fractionation (IMF) of isotopic SIMS analyses (Cameca 1280HR, CRPG Nancy) was predicted by response surface methodology (RSM) for the 18O/16O determination of plagioclase, K-feldspar, and quartz.

XPS and SIMS Analysis of Solid Electrolyte Interphases on Lithium Formed by Ether-Based Electrolytes

The chemical composition and microstructure of the solid electrolyte interphase (SEI) on lithium metal in ether-based electrolytes are investigated using X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (ToF-SIMS) and scanning electron microscopy (SEM). Electrolytes based on 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) solvents with lithium bis(trifluoromethane)sulfonamide (LiTFSI) conducting salt are employed to passivate lithium surfaces for different periods of time. Two types of model experiments (immersion-type and galvanostatic current load) are performed to generate self- and current-induced SEIs. Reference measurements of predicted SEI components and an advanced XPS signal coupling method facilitate the deconvolution of the spectroscopic and spectrometric data. Both ether solvents showed specific SEI formation for each experimental setup. DME appears to decompose immediately on the lithium surface and forms a thin passivation film of various salts in a lithium-alkoxide framework. DOL shows a slow SEI formation of organic and inorganic salts revealing problems in the lithium surface protection. Under current load the reaction rate is increased in DME maintaining the three-dimensional microstructure. For DOL the current load leads to a multi-layer structure of organic host materials comprising LiTFSI and lithium fluoride. Finally, two-dimensional schematic pictures of the SEI microstructure are developed.

Coordinated U–Pb geochronology, trace element, Ti-in-zircon thermometry and microstructural analysis of Apollo zircons

We present the results of a coordinated SIMS U–Pb, trace element, Ti-in-zircon thermometry, and microstructural study of 155 lunar zircons separated from Apollo 14, 15, and 17 breccia and soil samples that help resolve discrepancies between the zircon data, the lunar whole rock history and lunar magma ocean crystallization models. The majority of lunar grains are detrital fragments, some nearly 1mm in length, of large parent crystals suggesting that they crystallized in highly enriched KREEP magmas. The zircon age distributions for all three landing sites exhibit an abundance of ages at ∼4.33Ga, however they differ in that only Apollo 14 samples have a population of zircons with ages between 4.1 and 3.9Ga. These younger grains comprise only 10% of all dated lunar zircons and are usually small and highly shocked making them more susceptible to Pb-loss. These observations suggest that the majority of zircons crystallized before 4.1Ga and that KREEP magmatism had predominantly ceased by this time. We also observed that trace element analyses are easily affected by contributions from inclusions (typically injected impact melt) within SIMS analyses spots. After filtering for these effects, rare-earth element (REE) abundances of pristine zircon are consistent with one pattern characterized by a negative Eu anomaly and no positive Ce anomaly, implying that the zircons formed in a reducing environment. This inference is consistent with crystallization temperatures based on measured Ti concentrations and new estimates of oxide activities which imply temperatures ranging between 958±57 and 1321±100°C, suggesting that zircon parent magmas were anhydrous. Together, the lunar zircon ages and trace elements are consistent with a ⩽300My duration of KREEP magmatism under anhydrous, reducing conditions. We also report two granular texture zircons that contain baddeleyite cores, which both yield 207Pb–206Pb ages of 4.33Ga. These grains are our best constraints on impact ages within our sample population, and suggest at least one large impact is contemporaneous with the most common time of magmatic zircon formation on the Moon’s crust visited by the Apollo missions.

Relative Stability of Thiolate and Selenolate SAMs on Ag(111) Substrate Studied by Static SIMS. Oscillation in Stability of Consecutive Chemical Bonds

The stability of chemical bonds at the molecule–metal interface is of fundamental importance for a majority of applications based on organic materials. It remains, however, extremely difficult to determine this stability using experimental and theoretical methods. A detailed analysis of the static SIMS (S-SIMS) data obtained for the homologous series of thiolate- and selenolate-based self-assembled monolayers (SAMs) on the Ag(111) substrate reveals positional oscillations in the stability of consecutive chemical bonds in the vicinity of the molecule–metal interface. The observed oscillations are much more pronounced compared to recently reported analogous data for the Au(111) substrate, which confirms the universal nature of this phenomenon and its strong dependence on the type of molecule binding atom (S or Se) and the substrate (Ag or Au). Importantly, such an analysis has not been conducted to date using any other technique, and this study not only reveals the universal mechanisms of molecule–metal int...

Assessing the fidelity of marine vertebrate microfossil δ18O signatures and their potential for palaeo-ecological and -climatic reconstructions

Conodont biogenic apatite has become a preferred analytical target for oxygen isotope studies investigating ocean temperature and palaeoclimate changes in the Palaeozoic. Despite the growing application in geochemically-based palaeoenvironmental reconstructions, the paucity or absence of conodont fossils in certain facies necessitates greater flexibility in selection of robust oxygen-bearing compounds for analysis. Vertebrate microfossils (teeth, dermal denticles, spines) offer a potential substitute for conodonts from the middle Palaeozoic. Vertebrate bioapatite is particularly advantageous given a fossil record extending to the present with representatives across freshwater to fully marine environments, thus widening the scope of oxygen isotope studies on bioapatite. However, significant tissue heterogeneity within vertebrates and differential susceptibility of these tissues to diagenetic alteration have been raised as potential problems affecting the reliability of the oxygen isotope ratios as palaeoclimatic proxies. Well-preserved vertebrate microfossils and co-occurring conodont fossils from the Upper Devonian and Lower Carboniferous of the Lennard Shelf, Canning Basin, Western Australia, were analysed using bulk (gas isotope ratio mass spectrometry, GIRMS) and in-situ (secondary ion mass spectrometry, SIMS) methodologies, with the latter technique allowing investigation of specific tissues within vertebrate elements. The δ18Oconodont results may be interpreted in terms of palaeolatitudinally and environmentally sensible palaeo-salinity and -temperature and provide a baseline standard for comparison against vertebrate microfossil δ18O values. Despite an absence of obvious diagenetic modification, GIRMS of vertebrate denticles yielded δ18O values depleted in 18O by 2–4‰ relative to co-occurring conodonts. SIMS analysis of dentine tissues exhibited significant heterogeneity, while hypermineralised tissues in both scales and teeth produced δ18O values comparable with those of associated conodonts. The susceptibility of permeable phosphatic fossil tissues to microbial activity, fluid interaction and introduction of mineral precipitates post-formation is demonstrated in the dentine of vertebrate microfossils, which showed significant heterogeneity and consistent depletion in 18O relative to conodonts. The hypermineralised tissues present in both teeth and scales appear resistant to many diagenetic processes and indicate potential for palaeoclimatic reconstructions and palaeoecological investigations.

Complementary study of the photoluminescence and electrical properties of ZnO films grown on 4H-SiC substrates

We have studied the photoluminescence and electrical properties of ZnO films grown epitaxially by atmospheric pressure MOCVD on 4H-SiC substrates. The dominating D°X line on the low temperature PL spectrum is attributed to the emission of an exciton bound to the neutral donor. The intensity of this line correlates with the electrical properties of the films: the decrease of D°X intensity occurs simultaneously with the increase of the carrier׳s mobility. This we explain as donor activation providing free electrons to the conduction band. Based on the comparison of the calculated value of donor binding energy, the literature data and complementary SIMS analysis a suggested donor impurity is aluminum (Al). The exciton localization energy is 16.3meV, and agrees well with localization energy of 15.3meV for Al impurity reported by other authors (e.g. Ref. [33]). The thermal activation energy ED=22meV, determined from the Hall data and is in agreement with the optical activation energy ~20 meV, which is derived from the temperature-dependent PL study. The calculated value of the donor binding energy of 54.3eV is in agreement with the ionization energy of 53meV mentioned in earlier reports for Al in ZnO films. Our results prove that the commonly observed line at ~3.3599eV on low temperature PL spectra of ZnO is a neutral donor bound exciton emission due to the Al impurity.

Highly Mg-doped GaN dots and films grown by VLS transport at low temperature

In this study, a new approach toward localized p-type doping of GaN was explored by implementing vapor–liquid–solid (VLS) transport for both reducing the growth temperature and reaching very high Mg incorporation levels. The starting seeds are GaN(0001) epilayers grown on Si(111). The growth cycle includes three steps. At first, Ga is deposited by MOCVD onto the GaN surface, resulting in a network of Ga droplets with sub-micrometer diameters. Then, Mg is incorporated into the droplets, from the gas phase, using (MeCP)2Mg precursor. Finally, droplets are nitridated at 600–700 °C in flowing NH3. Performing one complete growth cycle leads to a network of well-separated dots and/or ring-shaped GaN features. It is demonstrated that the Mg content in the droplets drastically influences the GaN growth mode. Increasing Mg incorporation promotes growth at the liquid/solid interface versus growth at the triple line. To improve the seed coverage, several successive cycles have been performed leading to GaN films with thickness up to ∼250 nm. SIMS analyses demonstrate the very high incorporation of Mg in the VLS-grown material, with concentrations from 3 × 1019 to 8 × 1021 cm−3. Nevertheless, pronounced O incorporation (a few 1020 cm−3) is also found.

Nature of three Proterozoic (1680 Ma, 1230 Ma and 775 Ma) mafic dyke swarms in North China: Implications for tectonic evolution and paleogeographic reconstruction

Three Proterozoic mafic dyke swarms are identified in the periphery of the Yan-Liao rift in eastern Hebei Province, and all these dykes intruded the Archean basement with clear chilled margins. Precise U–Pb SIMS analysis yields 207Pb/206Pb average ages of 1677±12Ma (baddeleyite), 1236±7Ma (baddeleyite), and 775±5Ma (zircon) for the representatives, which all exhibit ages of crystallization. These dykes are referred to as Tujiagou (∼1680Ma; NW trending, >20m wide for each), Maojiagou (∼1230Ma; 0°–10° trending, around 40m wide), and Dingjiagou (∼775Ma; 30°–70° trending, 12–20m wide) dyke swarms, respectively.All these dykes are diabase, showing ophitic texture and mineral assemblages that are mainly composed of plagioclase and clinopyroxene, and underwent various degrees of epidotization, chloritization, and uralitization. They are tholeiitic (for the 1680Ma and 775Ma dykes) and alkaline (for the 1230Ma dykes) in composition, with different degrees of fractionation and indistinctive crustal contamination. The Tujiagou dykes (1680Ma) have low Mg# (44–49) and show negative Sr− anomalies and minor negative Eu− anomalies (Eu/Eu∗=0.91–0.96), which indicate clinopyroxene- and plagioclase-dominated fractionation. They exhibit (La/Yb)N of 5.3–7.7 and are depleted in some HFSEs, such as Zr and Hf. The Maojiagou dykes (1230Ma) present relatively high Mg# values with the fractionation of clinopyroxene. The dykes exhibit light REE enrichment ((La/Yb)N=6.48–12.8) and slight or no depletion in HFSEs. Both the 1680Ma and 1230Ma dykes exhibit similar εNd(t) values (−1.9 to 1.3), indicating similarly depleted mantle sources. The Dingjiagou dykes (775Ma) show negative Eu− anomalies (0.88–1.07) and negative Ce− anomalies with medium light REE enrichment ((La/Yb)N=2.3–4.12). They are depleted in HFSEs such as Nb, Ta, Zr, etc. and have enriched εNd(t) values (−7.2 to −5.1). The Mg# values are 47–60. The 775Ma dykes could be from the metasomatized sub-continental lithospheric mantle and have experienced plagioclase-dominated fractionation.The 1680Ma Tujiagou dykes are coeval and chemically similar to and could be equivalents of the Laiwu dykes in Luxi. The 1230Ma Maojiagou dykes are similar to some other 1230–1210Ma mafic dykes/intrusions in this craton. The 775Ma Dingjiagou dykes are newly reported. These dyke swarms developed in an area adjacent to the Yan-Liao rift, and could represent a stepwise rifting in the northern parts of the craton. In a global scale, these dyke swarms could be potential geological records that were dismembered during the breakup of supercontinents and are markers to paleogeographic reconstruction. Specifically, the 1230Ma dykes, which are comparable with the synchronous Sudbury dykes in Laurentia, could be parts of a large igneous province. The North China Craton separated from the Laurentia only until approximately 775Ma. However, this hypothesis must be confirmed further, particularly in paleomagnetic studies.

Boric acid solution concentration influencing p-type emitter formation in n-type crystalline Si solar cells

Boric acid (BA) is a spin on dopant (BSoD) source which is used to form p+ emitters in n-type c-Si solar cells. High purity boric acid powder (99.99% pure) when mixed with deionized (DI) water can result in high quality p-type emitter with less amount of surface defects. In this work, we have used different concentrations of boric acid solution concentrations to fabricate p-type emitters with sheet resistance values < 90 Ω/□. The corresponding junction depths for the same are less than 500 nm as measured by SIMS analysis. Boron rich layer (BRL), which is considered as detrimental in emitter performance is found to be minimal for BA solution concentration less than 2% and hence useful for p-type emitter formation.

Intact lipid imaging of mouse brain samples: MALDI, nanoparticle-laser desorption ionization, and 40keV argon cluster secondary ion mass spectrometry.

We have investigated the capability of nanoparticle-assisted laser desorption ionization mass spectrometry (NP-LDI MS), matrix-assisted laser desorption ionization (MALDI) MS, and gas cluster ion beam secondary ion mass spectrometry (GCIB SIMS) to provide maximum information available in lipid analysis and imaging of mouse brain tissue. The use of Au nanoparticles deposited as a matrix for NP-LDI MS is compared to MALDI and SIMS analysis of mouse brain tissue and allows selective detection and imaging of groups of lipid molecular ion species localizing in the white matter differently from those observed using conventional MALDI with improved imaging potential. We demonstrate that high-energy (40 keV) GCIB SIMS can act as a semi-soft ionization method to extend the useful mass range of SIMS imaging to analyze and image intact lipids in biological samples, closing the gap between conventional SIMS and MALDI techniques. The GCIB SIMS allowed the detection of more intact lipid compounds in the mouse brain compared to MALDI with regular organic matrices. The 40 keV GCIB SIMS also produced peaks observed in the NP-LDI analysis, and these peaks were strongly enhanced in intensity by exposure of the sample to trifluororacetic acid (TFA) vapor prior to analysis. These MS techniques for imaging of different types of lipids create a potential overlap and cross point that can enhance the information for imaging lipids in biological tissue sections.Graphical abstractSchematic of mass spectral imaging of a mouse brain tissue using GCIB-SIMS and MALDI techniquesElectronic supplementary materialThe online version of this article (doi:10.1007/s00216-016-9812-5) contains supplementary material, which is available to authorized users.

Fabrication of lateral porous silicon membranes for planar microfluidics by means of ion implantation

We introduce a new fabrication method based on ion implantation to create lateral porous silicon membranes and integrate them into planar microfluidic devices. Our proposed method relies on the fact that the formation of porous silicon by anodization highly depends on the dopant type and concentration, which can be manipulated by ion implantation. In order to confine the porosification at desired locations within silicon steps bridging microchannels, we use boron and phosphorus implantation to respectively create a p++ layer buried in an n-type silicon substrate, and a protective n-type surficial layer. The use of a metal electrode patterned onto the silicon step for current injection during anodization enables pores to propagate laterally during the membrane formation. The optimal implantation doses and energies leading to the required boron and phosphorus profiles are determined by means of process simulation and further confirmed by SIMS analysis. We demonstrate that the proposed fabrication process leads to the creation of lateral porous silicon membranes with open-ended pores adequately bridging microchannels and that we are able to manipulate the pore size (∼3–30nm) and membrane porosity (∼15–65%) by adjusting the current density during anodization. The adequate dead-end filtration capability of the fabricated membranes was tested and demonstrates the interest of the presented fabrication process for microfluidic applications.

Uniform annealing effect of electron irradiation on ferromagnetic GaMnAs thin films

For more than a decade, researchers have been searching for means to improve the Curie temperature of ferromagnetic GaMnAs samples, among which post-growth annealing in furnace has been treated as the most important one. In this work, we demonstrate that the Curie temperature can be improved by electron irradiation for the first time. Different doses of electron irradiation (1×1014,1×1015 and1×1016electrons/cm2) at 1.7MeV were applied, the enhancement of magnetic and electrical properties of ferromagnetic GaMnAs films was experimentally confirmed by HR-XRD, SQUID and Magneto-transport measurements. Further SIMS characterizations and analyses reveal that electron irradiation causes bi-directional out-diffusion and redistribution of compensating Mn interstitials towards both the upper surface and the lower interface, a newly found uniform effect clearly different from that of conventional post-growth annealing. The technique of electron irradiation annealing may provide an alternative way to improve the properties of electronic and magnetic compounds such as GaMnAs films.