Hubert Gnaser

RPTU - Rheinland-Pfälzische Technische Universität Kaiserslautern Landau | TUK · Department of Physics

Carbon cluster dianions (C7)²⁻ and (C10)²⁻ were produced by sputtering of a graphite sample and detected by accelerator mass spectrometry (AMS). The collisional activation of these dianions was studied via their interaction with He gas in an ion beam cooler device which is part of the AMS instrument. Contrary to the respective monoanion cluster, th...

In secondary ion mass spectrometry (SIMS), the detection of large organic molecules is accomplished using cluster ion bombardment. Ion formation often proceeds via cationization, through the attachment of (alkali) metal ions to the molecule. To study this process, the emission of secondary ions sputtered from polyethylene glycol (PEG) samples with...

In an attempt to investigate the possibility of an in situ cationization of molecular ions in time-of-flight secondary ion mass spectrometry, low-energy 500 eV Cs⁺ ions were implanted in organic materials before their analysis by Bi3⁺ cluster bombardment. Specifically, three different organic samples were used: arginine, leu-enkephalin, and polyeth...

In secondary ion mass spectrometry (SIMS), the detection of large organic molecules is accomplished using cluster ion bombardment. Ion formation often proceeds via cationization, through the attachment of (alkali) metal ions to the molecule. To study this process and its efficiency, the emission of secondary ions sputtered from polyethylene glycol...

Up to now, no consensus exists about the electronic nature of phosphorus (P) as donor for SiO2- embedded silicon nanocrystals (SiNCs). Here, we report on hybrid density functional theory (h-DFT) calculations of P in the SiNC/SiO2 system matching our experimental findings. Relevant P configurations within SiNCs, at SiNC surfaces, within the sub-oxid...

The formation of molecular hydrogen anions (H2⁻, D2⁻, HD⁻, H3⁻, HD2⁻, and D3⁻) was investigated. These anion species were produced by sputtering of TiD2 and HfH2 targets with Cs⁺ ions and were identified by secondary-ion mass spectrometry (SIMS), yielding the corresponding abundance distributions. The intensity ratios of both the diatomic (HD⁻/D2⁻)...

The emission of sputtered ions from isoleucine and leucine specimens under bombardment by 10 keV argon gas-cluster ions Ar1000+ was investigated by orthogonal time-of-flightsecondary ion mass spectrometry, in an attempt to examine the possibility of discriminating these amino acids by means of specific differences in their mass spectra. Apart from...

We report on phosphorous (P) doping of Si nanocrystal (SiNC)/SiO2 systems [1]. Relevant P configurations within SiNCs, at SiNC surfaces, within the sub-oxide interface shell and in the SiO2 matrix were evaluated by hybrid density functional theory (h-DFT). Atom probe tomography (APT) and its statistical evaluation provide detailed spatial P distrib...

Surfaces of InP(1 0 0) were bombarded by 2.1 keV Ar+ ions under normal incidence. The total accumulated ion fluence the samples were exposed to was varied roughly from 1 × 1017 cm−2 to 3 × 1018 cm−2 while ion fluxes in the range of (0.1−2) × 1014 cm−2 s−1 were used. The surface morphology resulting from these ion irradiations was examined by scanni...

Surfaces of InP were bombarded by 1.9keV Ar(+) ions under normal incidence. The total accumulated ion fluence the samples were exposed to was varied from 1×10(17)cm(-2) to 3×10(18)cm(-2) and ion flux densities f of (0.4-2)×10(14)cm(-2)s(-1) were used. Nanodot structures were found to evolve on the surface from these ion irradiations, their dimensio...

Ten pure amino acid specimens (alanine, arginine, asparagine, glutamine, glutamic acid, isoleucine, leucine, phenylalanine, threonine, and tyrosine) and three binary mixtures (phenylalanine/tyrosine, phenylalanine/arginine, and arginine/tyrosine) were bombarded by 10 keV argon gas-cluster ions Ar1000+ and the sputter-induced emission of positive se...

Up to now, no consensus exists about the electronic nature of phosphorus (P) as donor for SiO2-embedded silicon nanocrystals (SiNCs). Here, we report on hybrid density functional theory (h-DFT) calculations of P in the SiNC/SiO2 system matching our experimental findings. Relevant P configurations within SiNCs, at SiNC surfaces, within the sub-oxide...

We study the electronic properties of phosphorus doped Si nanocrystal/SiO2 superlattices and determine the carrier concentration by transient current analysis. This is achieved by encapsulating the multilayers between two electrical insulation layers and controlling the carrier mobility by a defined layer to layer separation. A saturation of the vo...

Atom probe tomography (APT) constitutes a rather unique analytical technique for the 3D elemental characterization of solid materials with potentially sub-nm spatial resolution. APT is, therefore, very well suited for the analysis of a nanostructured specimen such as matrix-embedded nanoparticles, ultra-thin films and junctions, grain boundaries, a...

Surfaces of InP were bombarded by 1.9 keV Ar(+) ions under normal incidence. The total accumulated ion fluence Φ the samples were exposed to was varied from 1 × 10(17) cm(-2) to 3 × 10(18) cm(-2), and ion fluxes f of (0.4 - 2) × 10(14) cm(-2) s(-1) were used. The surface morphology resulting from these ion irradiations was examined by atomic force...

Glass surfaces were patterned by milling periodic trench structures with wavelengths from 150 to 750 nm in a focused ion-beam (FIB) system. Upon exposure to 30 keV Ga+ ion irradiation under an incidence angle of 52° with respect to the surface normal, those patterns were found to transform into “ripple”-like nanostructures. Their evolution was moni...

We simulate the impact of an Ar1000 cluster (energy 10 keV, impact angle 55°) into an amorphous l-phenylalanine target. By use of a ReaxFF potential, it is possible to model not only the emission dynamics of intact Phe molecules but also the fragmentation and reaction pathways taken. The simulated sputter yield is in close agreement with experiment...

Large Arn+ cluster ions (with n ∼ 1500 Ar atoms per cluster) with a bombarding energy of 10 keV were used to investigate the sputter-induced emission of positive secondary ions from a phenylalanine specimen by orthogonal time-of-flight SIMS. An abundant flux of phenylalanine cluster ions (Mn + H)+ with n ≤ 12 was observed. The yield of dimers relat...

In the preceding paper an approach was described that allows measured secondary-ion energy spectra to be correlated with the original energy distribution. Here the model was applied to analyse energy spectra of Cs+ ions sputtered from a Cs bombarded Si sample. The aim was to show that relevant properties of the employed IMS-4f sector field mass spe...

Silicon nanocrystals (SiNCs) embedded in a silicon oxide matrix were studied by 3D atom probe tomography (APT). The distribution of the SiNC diameter was found to have a mean value of 3.7 ± 0.8 nm. The elemental composition of these particles was determined by employing two different approaches: (i) The proximity histogram method and (ii) a cluster...

Die Charakterisierung von Strukturen der heutigen Dünnschicht- und Nanotechnologie fordert die zur Verfügung stehenden instrumentellen Oberflächen- und Schichtanalysetechniken bis an die Grenzen ihrer Möglichkeiten. Nachweisempfindlichkeit und Ortsauflösung der etablierten Verfahren reichen inzwischen manchmal nicht mehr aus, um den Anforderungen i...

The displacement of atoms in a magnetic trilayer Fe (10 nm)/Cr (0.7 nm)/Fe (10 nm) system by 30 keV Ga+ ion irradiation was studied by 3D Atom Probe Tomography (APT). From APT, the positions of individual Cr and Fe atoms could be located with sub-nm spatial resolution, both before and after ion bombardment. In the pristine specimen the presence of...

Die Atomsonden – Tomografie gewinnt vor allem mit Blick auf die ständig steigenden Anforderungen an die Leistungsfähigkeit der Analyseverfahren in der Nanotechnologie in den letzten Jahren deutlich an Bedeutung. Die heute verfügbaren Präparations- und Analysegeräte gestatten den Einsatz der Atomsonden-Tomografie auch für technische Proben und biete...

The analysis of organic and biological substances by secondary ion mass spectrometry (SIMS) has greatly benefited from the use of cluster ions as primary bombarding species. Thereby, depth profiling and three-dimensional (3D) imaging of such systems became feasible. Large Arn (+) cluster ions may constitute a further improvement in this direction....

The emission of positive secondary ions from four amino acids (arginine, glycine, phenylalanine, and tyrosine) and from NaCl under irradiation with large Arn+ cluster ions was investigated by time-of-flight secondary ion mass spectrometry. Size-selected 5.5-keV Arn+ cluster ions with 300 ≤ n ≤ 2000 were used, and the flux of sputtered positive ions...

The energy spectra of Cs+ ions sputtered from silicon under 5.5-keV Cs+ bombardment were recorded for emission energies E ≤ 100 eV. The emitted ions were detected in a high-sensitivity double-focusing SIMS (Cameca IMS-4f). The influence of several instrumental parameters on the energy resolution and the peak position of the measured spectra were in...

Ion-bombardment effects in a magnetic trilayer Fe (10 nm)/Cr (0.7 nm)/Fe (10 nm) system have been studied by 3D atom probe tomography (APT). The films were bombarded by 30 keV Ga+ ions at low fluences. From APT, the positions of individual Cr and Fe atoms could be located with sub-nm spatial resolution, both before and after ion bombardment. In the...

SiGe alloy, owing to its high electron and hole mobility, has potential applications in high-speed microelectronic device technology. The optimization of such technology requires the precise determination of Ge concentration in the full range of composition and the understanding and control of the Ge–Si interdiffusion phenomenon. The most appropria...

The irradiation of glass surfaces by 30 keV Ga+ ions under oblique incidence angles results in the development of “ripple”-like nanostructures. The evolution of these ripples was monitored in situ in the ion fluence range from 3 × 1016 to 1 × 1018 Ga+ ions/cm2 using a focused ion beam system which incorporates a scanning electron microscope. With i...

Measurements of Si2+ and Si+ ions sputtered due to bombardment of 3–5 keV Ar+ ions on silicon substrate have been performed for understanding exact charge-state formation mechanisms. Examination on the penetration depth dependence of incident particle on secondary ion formation has been performed. A closure look at the energetics of the secondary i...

The analysis of organic and biological substances by secondary-ion mass spectrometry (SIMS) has greatly benefited from the use of cluster ions as primary bombarding species. Thereby, depth profiling and three-dimensional (3D) imaging of such systems became feasible. Large Ar(n)(+) cluster ions may constitute a further improvement in this direction....

SiGe alloy, owing to its high electron and hole mobility, has potential applications in high-speed microelectronic device technology. The optimization of such technology requires the precise determination of Ge concentration in the full range of composition and the understanding and control of the Ge–Si interdiffusion phenomenon. The most appropria...

The influence of the ion irradiation by 30 keV Ga + ions on the crystal structure, chemical ordering, magnetic properties, and topography of epitaxial Fe/Cr/Fe trilayers was investigated by different analytical techniques. We present direct experimental evidence, supported by theoretical estimates, that two processes take place concurrently due to...

The radioisotope 182Hf (t1/2=8.9Ma) is of great interest for astrophysical applications as a chronometer for the early solar system or as possible live supernova remnant on earth. However, AMS measurements of 182Hf are seriously influenced by the presence of the stable isobar 182W, which cannot be separated at typical AMS energies. Previous studies...

We present the results of a Coulomb explosion experiment that allows for the imaging of the rovibrational wave function of the metastable H2- ion. Our measurements confirm the predicted large internuclear separation of 6 a.u., and they show that the ion decays by autodetachment rather than by spontaneous dissociation. Imaging of the resulting H2 pr...

Nanocrystalline TiO2 films were prepared from colloidal suspensions using a mixture of anatase and rutile TiO2 particles. Their structure was examined by X-ray diffraction (XRD). The as-prepared specimens exhibit the presence of both anatase and rutile crystallites with average sizes of ∼30 and ∼50 nm, respectively, as determined from their charact...

The emission-energy spectra of atomic and molecular secondary ions sputtered from various metals and semiconductors (Al, Cu, In, Si, InP, and InSb) under 5.5-keV Cs+ irradiation were investigated. The emitted ions were detected in a high-sensitivity double-focusing secondary-ion mass spectrometer. Specifically, the energy distributions of Cs+, Cs2+...

Focused ion beam implantation of 30 keV Ga+ ions in single-crystalline InP was investigated by SIMS, using Cs+ primary ions for sputtering. Nine different implantation fluences ranging from 1 × 1013 to 1 × 1017 Ga+ ions/cm2 were used, with implanted areas of 50 × 50 µm2. The Ga concentration distributions of these implants were determined by SIMS d...

The bombardment of the surface of a solid by energetic ions often results in pronounced surface modifications, leading to characteristic topographical features. In this report, the development of specific morphological nanostructures on surfaces under ion irradiation is discussed. The following aspects will be emphasized: (i) on an atomic scale, th...

The emission of negatively charged HfFn- (n <= 5) and WFn- (n <= 7) molecular ions sputtered from a mixed Hf-W-PbF2 fluoride sample by a 13 keV Cs+ ion beam was studied. The emitted ions were detected in a high-sensitivity double-focusing secondary ion mass spectrometer. In the HfFn- and WFn- series, HfF5- and WF6- are the anions formed most abunda...

The emission of negatively charged ions from different fluoride samples (Li2SiF6, KBF4, KPF6, K2TiF6, PbF2, and W-PbF2) induced by sputtering with a 14.5-keV Cs+ ion beam was studied. Sputtered ions were detected in a high-sensitivity double-focusing mass spectrometer. A distinct flux of molecular anions of the type MFn- (n being the number of F at...

The implantation and retention of Cs atoms during low-energy irradiation of different materials (Si, Ge, and InP) was investigated by dynamic computer simulations using the Monte-Carlo code T-DYN that takes into account the gradual change of the target composition due to the Cs irradiation. The Cs incorporation was studied for four impact energies...

The implantation of Cs atoms in silicon was investigated by dynamic computer simulations using the Monte-Carlo code T-DYN that takes into account the gradual change of the target composition due to the Cs irradiation. The incorporation of Cs atoms was studied for incidence angles ranging from 0° to 85° and for four impact energies (0.2, 0.5, 1 and...

The photocatalytic degradation of methylene blue and 4-chlorophenol on nanocrystalline TiO2 (nc-TiO2) under UV irradiation was investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Nanocrystalline TiO2 films were prepared from suspensions containing TiO2-crystallites of different average sizes, the smallest one being 12 nm. The...

Focused ion beam implantation of 30-keV Ga+ ions in single-crystalline Si and Ge was investigated by SIMS, using Cs+ primary ions for sputtering. Nine different implantation fluences ranging from 1 × 1013 to 1 × 1017 Ga+-ions/cm2 were used, with implanted areas of 40 × 40 µm2. The Ga concentration distributions of these implants were determined by...

The incorporation of Cs atoms in silicon was investigated by dynamic computer simulations using the Monte-Carlo code T-DYN that takes into account the gradual change of the target composition due to the Cs irradiation. The implantation of Cs atoms at normal incidence was studied for four energies (0.2, 0.5, 1, and 3 keV) and three different Cs surf...

Titanium oxide films were prepared by annealing DC magnetron sputtered titanium films in an oxygen ambient. X-ray diffraction (XRD), Auger electron spectroscopy (AES) sputter profiling, MCs+-mode secondary ion mass spectrometry (MCs+-SIMS) and atomic force microscopy (AFM) were employed, respectively, for the structural, compositional and morpholog...

The small doubly-charged molecular anion SiF62− was studied by two distinct approaches, one experimental the other theoretical. The dianion was produced in the gas phase by sputtering a Li2SiF6 specimen with Cs+ ions and was detected by means of accelerator mass spectrometry. The identification was via the 29Si19F62− isotopomer; it has an odd total...

Focused ion beam implantation of 30-keV Ga+ ions in nanocrystalline diamond films was investigated by secondary-ion mass spectrometry (SIMS), using Cs+ primary ions for sputtering. Nine different implantation fluences ranging from 1×1013 to 1×1017 Ga+-ions/cm2 were used, with implanted areas of 40×40μm2. The Ga concentration distributions of these...

The proteins lysozyme, amylase, and bovine serum albumin (BSA) were adsorbed on two experimental dental materials, made of fluoroapatite particles embedded in polymer matrices, and on silicon wafers. The protein films were prepared as single-component layers, as binary mixtures, and as double layers. These systems were investigated by time-of-fligh...

The isotopic fractionation of C− and anions sputtered from graphite by 14.5-keV Cs+ bombardment was investigated by high-resolution mass spectrometry. Specifically, the 13C−/12C− and the 13C12C−/12C12C−ratios were monitored under steady-state sputtering conditions for different emission energies, ranging from ∼ 0 eV to about 55 eV. Generally, the h...

Emission of MCsn+ (n=1, 2, … etc.) molecular ions has been studied under the joint influence of electropositive (cesium) and electronegative (oxygen) elements in the secondary ion mass spectrometry (SIMS) process. The kinetic energy distributions, measured for Cs+, Cs2+, AgCs+ and AgCs2+ ions at different oxygen pressures exhibited changing slopes...

Nanocrystalline anatase TiO2 films were prepared from colloidal suspensions using particles with a nominal size of 12nm. Their structure was examined by Raman spectroscopy and X-ray diffraction (XRD). The as-prepared specimens exhibit exclusively features due to the anatase phase of TiO2 (e.g., the Eg, B1g and A1g vibration modes in Raman spectrosc...

Energy and angular distributions of sputtered species from a wide variety of target materials (metals, semiconductors, alkali halides, frozen gases, and organic solids) are discussed. Bombardment energies in the range from a few 10 eV to roughly 100 keV are considered, covering irradiation conditions for which nuclear (elastic) collisions dominate...

“The techniques and equipment developed for AMS studies are well suited for identifying exotic negative ions”. With this sentence begins a pioneering paper by Roy Middleton and Jeff Klein (M&K) on small doubly-charged negative carbon clusters [Nucl. Instr. and Meth. B 123 (1997) 532]. M&K were the first to utilize Accelerator Mass Spectrometry to p...

Nanocrystalline anatase TiO2 films were prepared from colloidal suspensions using particles with a nominal size of 12 nm. Their structure was examined by Raman spectroscopy and X-ray diffraction (XRD). The as-prepared specimens exhibit exclusively features due to the anatase phase of TiO2 (e.g., the Eg, B1g and A1g vibration modes in Raman spectros...

The detection of small doubly-charged molecular anions by means of highly sensitive mass spectrometry is discussed. The production of these gas-phase dianions is accomplished by sputtering the specimen with Cs+ ions with an energy of a few keV. It is demonstrated that dianions can be detected most easily when the molecular ion has an odd total mass...

Nanocrystalline anatase TiO2 films were prepared from colloidal suspensions using particles with a size of 12 nm. Their structure was examined by Raman spectroscopy and X-ray diffraction (XRD). The as-prepared specimens exhibit exclusively features due to the anatase phase of TiO2 (e.g., the Eg, B1g and A1g vibration modes in Raman spectroscopy and...

The emission of MCs+ secondary ions (M designates the analyte species) from TiOx (0.2≤x≤2) and GeOx (0.001≤x≤0.8) films under Cs+ bombardment was examined. The relative calibration factors of OCs+/TiCs+ and OCs+/GeCs+ were determined and were found to depend pronouncedly on the O/Ti and O/Ge atomic concentration ratios. Specifically, with increasin...

Nanocrystalline TiO2 is known to be a very efficient photocatalyst. In order to elucidate the details of reaction pathways occurring on the surface, nanocrystalline TiO2 films (with 12nm average crystallite size) were covered by methylene blue (MB) and studied, both in the pristine state and upon UV exposure, by TOF-SIMS. Distinct mass signals rela...

The lifetimes of three isotopologs of the molecular hydrogen anion have been measured using an electrostatic ion-beam trap. Much longer lifetimes (up to {approx}2 ms for D{sub 2}{sup -}) than predicted by the most recent calculation are found, and it is proposed that more than one electronic state contributes to the overall lifetimes of these speci...

The lifetimes of three isotopologs of the molecular hydrogen anion have been measured using an electrostatic ion-beam trap. Much longer lifetimes (up to ˜2ms for D2- ) than predicted by the most recent calculation are found, and it is proposed that more than one electronic state contributes to the overall lifetimes of these species.

The existence of long-lived (metastable) molecular hydrogen anions H{sub 2}{sup -}, D{sub 2}{sup -}, H{sub 3}{sup -}, and D{sub 3}{sup -} is demonstrated. These anion species were produced by sputtering of TiD{sub 2} or HfH{sub 2} targets with Cs{sup +} ions and were identified by secondary-ion mass spectrometry (SIMS). From the respective flight t...

Thermal desorption spectroscopy (TDS) under ultra high vacuum (UHV) condition has been used to investigate the desorption characteristics of Cu/CeO2/γ-Al2O3 thin film catalysts coated onto the microchannel of a microreactor. TDS results demonstrate that surface desorption profiles and chemical properties (acid–base and redox properties) are remarka...

The use of tandem accelerators for accelerator mass spectrometry (AMS) allows to literally "analyze" molecules. When a molecular ion with mass M and charge Q is injected at the low-energy side, it is efficiently broken up into its atomic constituents during the stripping process in the terminal. At the high-energy side the positively charged atomic...

Nanocrystalline TiO2 (anatase) films were prepared using either colloidal suspensions or a sol–gel route. The electronic structure of these films was analyzed using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Apart from pristine films, films containing defects introduced by annealing under ultra-high vac...

Photocatalytic degradation reactions of methylene blue on nanocrystalline TiO2 (nc-TiO2) films were studied in situ by surface mass spectrometric techniques including secondary ion mass spectrometry, laser desorption direct ion mass spectrometry, and laser desorption/laser photoion mass spectrometry. The parent ion of methylene blue and/or its redu...

The existence of (metastable) molecular hydrogen anions H2(-), D2(-), and H3(-) is demonstrated. These anion species were produced by sputtering of TiH2 and TiD2 targets with Cs+ ions and were identified by accelerator mass spectrometry. From the respective flight times through the spectrometer, lifetimes for H2(-) and D2(-) of at least 3 micros an...

The investigation of nanocrystalline anatase TiO2 films with different crystallite sizes, in terms of their structure, chemical composition, electrical properties and the thermal desorption of O2, was discussed. The frequency-dependent complex resistance of the films was determined by utilizing impendance spectroscopy. The XRD and TEM analysis indi...

The activity behavior of steam reforming of methanol was studied over Cu/CeO2/γ-Al2O3 catalysts with different compositions in a parallelized 10-channel microreactor. It was found that the catalytic performance is strongly influenced by the catalyst compositions, i.e. copper and ceria loading. Cu/CeO2/γ-Al2O3 catalyst thin films before and after us...

Kinetic energy distributions of MCsn+ (n=0,1,2,3, …, etc.) molecular ions (M—target element of interest and Cs+—primary ion) emitted in the secondary ion mass spectroscopy process have been studied for various metallic samples (Al, Cu, and Ag) under varying Cs+ impact ion energies (1–5 keV). From the peak shifts of the energy distributions it is ar...

Steam reforming of methanol (SRM) was investigated over Cu/CeO2/γ-Al2O3 catalysts with different compositions in a parallelized 10-channel micro-structured reactor. The catalytic activity was found to be strongly dependent on the copper loading. The parallel screening result was tentatively discussed with surface analysis characterization results a...

Nanocrystalline anatase TiO2 films with crystallites of three different sizes (approximately 6, 12, and 18 nm) were deposited on various substrates (glass, sapphire, and silicon) using colloidal suspensions. These films were thoroughly characterized with respect to their surface morphology, crystal structure, phase homogeneity, elemental compositio...

Free doubly-charged negative molecules are a challenge for both theory and experiment. Their stability depends on a very delicate balance between interatomic structure, electronic interaction and Coulomb repulsion. Detecting di-anions of mass M with conventional mass spectrometry always bears the risk of erroneously measuring contributions from sin...

The detection of small molecular dianions by secondary-ion mass spectrometry (SIMS) and by accelerator mass spectrometry (AMS) is compared. In SIMS, the existence of these dianions can be identified safely if the total mass number of the molecule is odd and the dianion is hence detected at a half-integral mass number. The occurrence of fragmentatio...

Secondary-ion mass spectrometry (SIMS) was used for the characterization of the catalytically active parts of a microreactor, both before and after being used in the reactor. The catalyst coatings for the microreactor were prepared in a standard way: nanoporous washcoats were deposited on the microstructures by a particle route and the active compo...

In the present work, the existence of small molecular dianions of the form XC2−n (where X designates another element) produced by sputtering was investigated. Specifically, the possible emission of OC2−n, NC2−n, FC2−n and TiC2−n doubly charged ions in sputtering of appropriate specimens containing these elements (graphite, teflon, titanium carbide)...

A fundamental study concerning the preparation of porous alumina washcoats in microchannels for the application in heterogeneous gas phase catalysis was performed, focusing on the pre-treatment of the microstructures, properties, and adhesion of the washcoats as well as the testing of the prepared catalysts. Steel microstructures, which are manufac...

Heterogeneous gas phase catalyst screening with catalysts applied on titer-plates is presented. It will be shown that titer-plates can as well be used for the sample preparation outside the reactor and for the catalyst testing in the reactor. For the catalyst preparation, the known wash-coating-impregnation procedure is applied. An alumina coated p...

Two kinds of nanocrystalline alumina powders, boehmite (gamma-AlOOH, particle size d approximately 10 nm, BET surface area A(BET) = 180-200 m(2) g(-1)) and corundum (alpha-Al(2)O(3), d approximately 400 nm, A(BET) = 7 m(2) g(-1)) were used for comparative investigation by thermogravimetry (TG). The remarkable difference in the dehydration profiles...

Nanoporous thin films were deposited onto glass substrates by painting with a solution of nanocrystalline anatase TiO(2) particles (with a size of either 6 nm or 16 nm) suspended in an organic solvent. Upon drying in air for about 1 day, the films were tempered at 450 degrees C in air for 1 h. This procedure results in stoichiometric TiO(2) films w...

The yields of negatively charged carbon Cn− (n≤21) and silicon Sin− (n≤9) cluster ions sputtered by 14.5keV Cs+ ions from graphite and silicon, respectively, were monitored during the initial stages of Cs incorporation in the near-surface regions of the samples. The associated work function (WF) variations ΔΦ were determined in situ from the shifts...

The emission of negatively charged ions from different fluoride samples (LiF, CaF2, LaF3 and HfF4) induced by sputtering with a 14.5-keV Cs+ ion beam was studied. Sputtered ions were detected in a high-sensitivity double-focusing mass spectrometer. In particular, the possible existence of small doubly charged negative molecular ions was investigate...

Small doubly charged negative cluster ions OCn2− were studied both by experimental and by theoretical means. In the experiments these dianions (with n = 5–19) were produced by sputtering of a graphite specimen with a 14.5 keV Cs+ ion beam at an elevated oxygen partial pressure in the vicinity of the sample’s surface. The dianions and the correspond...

The first small doubly charged negative cluster ions OCn2- (with n=7–14) were produced by sputtering of a graphite specimen with a 14.5 keV Cs+ ion beam at an elevated oxygen partial pressure in the vicinity of the sample’s surface. These dianions and the corresponding singly charged OCn- (n<~21) cluster ions were detected in a double-focusing mass...

The detection limits of secondary-ion-mass spectrometry for carbon, nitrogen, and oxygen in silicon are determined and are shown to be as low as about 1×1014 atoms/cm3 for nitrogen and 2×1015 atoms/cm3 for carbon and oxygen. This very high sensitivity is achieved by an analytical approach: to suppress the interference from residual-gas adsorption o...

Titania films, doped with erbium, were fabricated on porous anodic alumina from a precursor. The samples, subjected to thermal processing up to 1270 K, exhibited strong luminescence at 1.53 μm associated with transitions of ions in the xerogel. The intensity of photoluminescence increased with the number of xerogel film depositions onto alu...

The yields of negatively charged carbon cluster ions Cn- (2<~n<~21) and Cn2- (n=8 and 10) emitted from graphite irradiated by 14.5keV Cs+ ions were monitored during the initial stages of Cs incorporation in the near-surface region of the specimen. The associated work-function variations ΔΦ were determined in situ from the shifts of the sputtered-io...

The charge-density distribution and the respective plasma potential distribution in an electrodeless low-pressure rf plasma as it is employed in electron-gas secondary-neutral mass spectrometry (SNMS) were determined theoretically by a comparatively simple plasma model. A second-order finite element program combines a Maxwell–Boltzmann like electro...

Secondary-ion mass spectrometry and secondary-neutral mass spectrometry use the atoms and molecules sputtered from the surface of a solid by energetic-ion impact to derive information on the elemental composition at the surface and, in conjunction with continuous sample erosion, in thin films. This contribution summarizes the basic principles of th...

The emission of negative cluster ions in sputtering of silicon, silicon carbide and graphite by 14.5 keV Cs+ ion bombardment was investigated by mass spectrometry. Specifically, for various homonuclear () and heteronuclear (SiCn−,Si2Cn−,CsCn−,CsSin−) anionic cluster species emission-energy spectra were recorded and their abundance distributions as...

Small doubly charged negative cluster ions SiC2-n (with n=6, 8, and 10) are produced by sputtering the surface of a SiC specimen with a 14.5-keV Cs+-ion beam. They are detected in a double-focusing mass spectrometer that covers a dynamic abundance range of about 109. The emission yields of these dianionic clusters amount to roughly 10-4 of the corr...