Focused ion beam implantation of Ga in Si and Ge: fluence‐dependent retention and surface morphology

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 SIMS depth profiling. Such 30‐keV Ga implantations were also simulated by a dynamic Monte‐Carlo code that takes into account the gradual change of the near‐surface composition due to the Ga incorporation. In both approaches, an essentially linear increase of the Ga peak concentrations with fluence is found up to ～1 × 10¹⁶cm^?2; for higher fluences, the Ga content approaches a saturation level which is reached at about (1–2) × 10¹⁷cm^?2. The measured and simulated peak concentrations of the Ga distributions are in good agreement. The most probable ranges obtained from the experiments correspond closely with the respective values from the simulations. The surface morphology caused by Ga⁺ implantation was investigated by atomic force microscopy (AFM). The AFM data indicate that for low fluences (<3 × 10¹⁵cm^?2) the surface within the implanted areas is growing outward (i.e. is swelling). For increasingly higher fluences, sputter‐induced erosion of the surface becomes dominant and distinct craters are formed for fluences above ～1 × 10¹⁶cm^?2. At the boundary of the implanted region a wall‐like structure is found to form upon Ga implantation; its height is growing with increasing fluence, reaching a value of ～15 nm at 1 × 10¹⁷ Ga⁺‐ions/cm². Copyright © 2008 John Wiley & Sons, Ltd.     

聚酞菁锗氧烷的电子辐照损伤及高分辨电子显微学研究

利用选区电子衍射观察了聚酞菁锗氧烷晶体的电子辐照损伤规律,结果表明,各晶面损伤次序既与所对应衍射班点的衍射级数有关,又与晶面间距有关。同时用选区电子衍射测量该聚合物晶体的耐电子辐照能力,对比不同加速电压对耐电子辐照能力的影响,讨论了获取晶面间距小于1nm的晶面的晶格像的可能性。最后利用高分辨电子显微技术拍摄了该聚合物的间距为0.66nm的晶格像和二维晶格像。     

Gas Electron Diffraction and its Influence on the Solution of the Phase Problem in Crystal Structure Determination

We studied, and performed research for our Ph.D. degrees in the area of gas electron diffraction. Our mentor was Lawrence Brockway. a pioneer in this subject. At that time, research in gas electron diffraction was in its early stages of development. In 1941, the distinguished Peter Debye wrote a theoretical paper concerning gas electron diffraction which challenged ones capability to develop the necessary experimental equipment and to further advance the theoretical developments so as to greatly extend the science of gas electron diffraction. We carried these thoughts in mind when we joined the Naval Research Laboratory, where the opportunity to design and produce excellent equipment was readily available. In the course of pursuing this research area, one of the findings was the existence of non-negativity as a condition for the results of a diffraction experiment for gaseous substances. When we became interested in the field of crystal structure determination, the familiarity with non-negativity which was needed in the study of gases, led to a search for the necessary and sufficient condition for a Fourier series to be non-negative. The search was successful and has played an important part in crystal structure determination. Some early applications to complicated structures are described.     

Phase formation and impurity effects in Ar+ ion irradiated Mo/Si thin film bilayer system

We report a dose‐dependent phase evolution in Mo/Si bilayer system upon Ar⁺ ion beam irradiation and subsequent flash annealing at 800 °C for 60 s. Micro‐structural characterization with Grazing Incidence X‐ray Diffraction and Raman scattering reveals a dose‐dependent nucleation of polymorphic phases occurring at the amorphized interface region. The ion beam mixing process has been investigated by Secondary Ion Mass Spectrometry and Rutherford Backscattering Spectrometry. While low ion doses favour nucleation of only metastable MoSi₂ phase, co‐existence of polymorphic phases are observed at high ion doses. The persistence of such polymorphic phases even after a high‐temperature anneal for high dose implanted specimen is indicative of phase retardation. The phase retardation of h‐MoSi₂ to t‐MoSi₂ is accounted in terms of nucleation and growth process. Copyright © 2012 John Wiley & Sons, Ltd.     

Combined use of ion beam slope cutting and scanning electron microscopy for the investigation of the 3-dimensional micro-structure of alterated mediaeval glass

Ion beam slope cutting (IBSC) has been developed as a preparation method for SEM and TEM to avoid the problems which occur using the common mechanical preparation techniques. IBSC has been practised on metals, plastic composites ceramics and alterated mediaeval glass, too. For the investigation of the 3-dimensional microstructure of the glass samples, IBSC has been the only method, which will enable a small cut without destroying the valuable cultural heritage. By SEM investigations of the ion beam cut, the alteration process of mediaeval glass has been observed starting on the surface and spreading into deeper zones of glass. Vertical and lateral cracks are only developing and spreading in the surroundings of crater erosions. The cracks cause splitting of parts near the surface of glass. Inside the cracks, harmful atmospheric gases, like SO₂ and CO₂, are reacting with the main glass components to alterations salts, which will build up a white and black crust on the surface and in zones near the surface.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Simultaneous determination of cobalt and chromium by ion chromatography with chemiluminescence detection and its application to glass analysis

A method is described for the simultaneous determination of very low levels of Co and Cr by high performance ion chromatography coupled with a chemiluminescence detection system. 0.1M K₂SO₄ solutions, adjusted to pH 3.0, were used as eluent to separate Co(II) and Cr(III) between them and from interferents. The detection system was the chemiluminescence of luminol/ H₂O₂ in alkaline medium catalyzed by such transition metals. Using a matrix solution analogous to soda-lime silica glass (dissolved in acids) calibration graphs were linear up to 0.5 ng ml^–1 for cobalt and up to 250 ng ml^–1 for chromium. The corresponding calculated detection limits (3 s) in such matrix were 0.05 ng ml^–1 and 15 ng ml^–1 for Co and Cr, respectively. The relative standard deviations were 1.4% at 0.5 ng ml^–1 Co level and 2.8% at the 200 ng ml^–1 Cr level. No interferences were observed from the more common metals, particularly those present in glass samples. The ion chromatography/ chemiluminescent method proposed has been successfully applied to the analysis of Co and Cr in glasses.     

Investigation of copper patinas using ion beam analysis and scanning electron microscopy

Ion beam analysis (IBA) techniques were applied successfully to the investigation of non‐corroded and artificially corroded patina layers grown on copper substrates in order to explore their potential use in the study of degradation phenomena of copper and copper alloys subjected to chemical treatment and exposed to selected environmental conditions. Rutherford backscattering spectroscopy (RBS) with deuterons as projectiles and the nuclear reactions ¹⁶O(d,p)¹⁷O and ³²S(p,p′γ)³²S were applied to the investigation of the depth distribution of oxygen and sulphur in near‐surface layers of synthetic patina consisting of mineral phases corresponding to chalcanthite as well as to cuprite + chalcanthite and antlerite + brochantite + chalcanthite. Electrochemical techniques (potentiodynamic polarization and cyclic voltammetry in 0.5 M Na₂SO₄) were used for artificial acceleration and study of the corrosion processes, and scanning electron microscopy (SEM/EDS) was used for examination of the surface morphology of the samples. A patinated roof sample from the Vienna Hofburg also was investigated using the same techniques. The measurement showed that IBA can provide valuable information for the study of patina near‐surface layers of thickness up to a few micrometres and indicated that cuprite was the mineral phase primarily formed on the copper substrates and the main component of the interface between the patina layer and the metallic substrate. The investigated copper patinas looked rather heterogeneous and were characterized by high porosity. Mixed patinas exhibited considerable stability to further corrosive attack. Copyright © 2005 John Wiley & Sons, Ltd.     

Direct Atomic-Level Imaging of Zeolites: Oxygen,Sodium in Na-LTA and Iron in Fe-MFI

Zeolites are becoming more versatile in their chemical functions through rational design of their frameworks. Therefore, direct imaging of all atoms at the atomic scale, basic units (Si, Al, and O), heteroatoms in the framework, and extra-framework cations, is needed. TEM provides local information at the atomic level, but the serious problem of electron-beam damage needs to be overcome. Herein, all framework atoms, including oxygen and most of the extra-framework Na cations, are successfully observed in one of the most electron-beam-sensitive and lowest framework density zeolites, Na- LTA . Zeolite performance, for instance in catalysis, is highly dependent on the location of incorporated heteroatoms. Fe single atomic sites in the MFI framework have been imaged for the first time. The approach presented here, combining image analysis, electron diffraction, and DFT calculations, can provide essential structural keys for tuning catalytically active sites at the atomic level.     

Three‐dimensional structural analysis of a block copolymer by scanning electron microscopy combined with a focused ion beam

A three‐dimensional (3D) lamellar structure of a poly(styrene‐block‐isoprene) block copolymer was observed at submicrometer and micrometer levels by scanning electron microscopy combined with a focused ion beam (FIB–SEM). The 3D lamellar structure with an exceptionally large periodicity, about 0.1 μm, was successfully reconstructed, and the size of the reconstructed image by FIB–SEM was 6.0 × 6.0 × 4.0 μm³, which was greater than the transmission electron microtomography data, 3.8 × 3.9 × 0.24 μm³, by a factor of about 40. This result indicates that 3D reconstruction using FIB–SEM is quite useful for direct 3D observations, especially analyses of polymeric materials at the submicrometer and micrometer levels. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 677–683, 2007     

The Molecular Structure and the Puckering Potential Function of Octamethylcyclotetrasilane,Si4Me8, Determined by Gas Electron Diffraction and Relaxation Constraints from Ab Initio Calculations

Gas electron diffraction data are applied to determine the geometrical parameters of the octamethylcyclotetrasilane molecule using a dynamic model in which the ring puckering is treated as a large amplitude motion. The structural parameters and parameters of the potential function were refined, taking into account the relaxation of the molecular geometry estimated from ab initio calculations at the Hartree–Fock level of theory using a 6-311G** basis set. The potential function has been described as V() = V ₀[(/ _e )² – 1]² with V ₀ = 1.0 ± 0.5 kcal/mol and _e = 28.3 ± 1.9°, where is the puckering angle of the ring. The geometric parameters at the minimum of V() (r _a in Å, in degrees and errors given as three times the standard deviations including a scale error) are as follows: r(Si—C)_av = 1.894(3), r(Si—Si) = 2.363(3), r(C—H) = 1.104(3), CSiC = 109.5(6), SiSiSi = 88.2(2), SiCH = 111.7(6), C = 4.1, where the tilt C was estimated from ab initio constraints. The structural parameters are compared with those obtained for related compounds.     

Reaction of SbPO4 with lithium in non-aqueous electrochemical cells: preliminary study and evaluation of its electrochemical performance in anodes for lithium ion batteries

SbPO₄, a phosphate with a layered structure, was tested as an electrode material for lithium cells spanning the 3.0-0.0 V range. Two main electrochemical processes were detected as extensive plateaus at ca. 1.6 and 0.7 V in galvanostatic measurements. The first process was found to be irreversible, thus excluding a potential intercalation-like mechanism for the reaction and being better interpreted as a decomposition reaction leading to the formation of elemental Sb. This precludes the use of this compound as a cathodic material for lithium cells. By contrast, the process at 0.7 V is reversible and can be ascribed to the formation of lithium-antimony alloys. The best electrochemical response was obtained by cycling the cell at a C/20 discharge rate over the voltage range 1.25-0.25 V. Under these conditions, the cell delivers an average capacity of 165 Ah/kg—a value greater than those reported for other phosphates—upon successive cycling.     

Li+3 ion beam irradiation induced changes in the thermodynamic and electrical parameters of 4-n-(nonyloxy) benzoic acid

Li⁺³ ion beam irradiation studies on 4-n-(nonyloxy) benzoic acid (NOBA) have been carried out. Thermodynamic measurements demonstrate that all the phase transition temperatures are depressed for low value of irradiation fluence as compared to those for the pure NOBA and thereafter increase linearly with increase in irradiation fluence. It has also been observed that the temperature range of N and SmC phases in the heating and cooling cycles is improved due to irradiation. Dielectric investigations show that both the transverse as well as the longitudinal components of the dielectric permittivity are increased as compared with those of the pure sample due to irradiation. The observed change in the thermodynamic and dielectric parameters is attributed to the increased concentration of NOBA monomers over the NOBA dimers due to fragmentation of the hydrogen bonding in some of the NOBA dimers.     

Electron microscopy of submicron particles in natural waters—Morphology and elemental analysis of particles in fresh waters

Submicron particles larger than about 0.1m in pond and river waters were collected on a carbon film mounted on a specimen grid by centrifugation and then studied morphologically and analyzed for major elements heavier than sodium, with a high-resolution transmission electron microscope equipped with an energy dispersive X-ray analyzer. If available, the data were compared with those of particles artificially prepared under various conditions. Four typical particles—aluminosilicate, quartz, fine-particle aggregates containing silica and iron(III) oxide, and microorganisms—were found in fresh waters.     

Molecular Structures of Acetylene Derivatives of Tin. VIII Trimethylstannylacetylene: Use of Results of Quantum-Chemical Calculations and Spectroscopic Measurements in Analysis of Gas-Phase Electron Diffraction Data

Structural analysis of electron diffraction data on trimethylstannylacetylene, (CH₃)₃SnCCH (1), obtained in the previous investigation (the nozzle temperature being 22°C), has been performed with consideration of nonlinear kinematic effects at the first-order level of perturbation theory (h1). The geometry and force field of 1 have been calculated by the RHF and MP2 (frozen core) methods. The effective core potential in SBK form and the optimized 31G* valence basis set have been applied in the case of Sn atom. The 6-311G** basis set have been used for carbon and hydrogen atoms. Vibrational spectra of the light and two deuterated isotopomers of 1 have been interpreted using the C _3v equilibrium molecular symmetry. For this purpose, the procedure of scaling the quantum-chemical force field by fitting the calculated frequencies to the experimental ones has been employed. The root-mean-square (RMS) vibrational amplitudes and shrinkage corrections used in the electron diffraction analysis have been calculated from the scaled quantum-chemical force field. It has been shown that flexibility of the linear fragment in 1 decreases considerably compared to that of the symmetrically substituted acetylene fragment in the (CH₃)₃SnCCSn(CH₃)₃ molecule (2). Using these data, we refined the geometrical parameters of 1 in terms of a static C _3v symmetry molecular model. The following r _h1 values have been obtained (the bond distances are given in Å and the valence angles in degrees): Sn—C_Me 2.147(7), Sn—C2.096(17), CC 1.237(11), C_Me—H (av.) 1.091(4), C_Me—Sn-C107.1(7), Sn—C_Me—H (av.) 113.4(6). The values in parentheses are experimental total errors including least-squares standard deviation values and scale uncertainties. The structural parameters of linear fragments in both ethynyl derivatives of Sn 1 and 2 are found to be virtually equal.     

High performance ultra trace analysis in molybdenum and tungsten accomplished by on-line coupling of ion chromatography with simultaneous ICP-AES

For the characterisation of trace elements in high purity Mo and W analytical methods with a detection limit in the ng/g-range have to be used. Today mass spectrometric methods are state of the art for such applications. However, these methods in case of refractory metal analysis are time consuming, expensive, limited by isobaric interferences and therefore not very suitable for quality control in an industrial laboratory. With respect to these drawbacks a cost and time efficient method was developed by on-line coupling of an ion chromatographie system to a simultaneous ICP-AES (Inductively Coupled Plasma — Atomic Emission Spectrometry) instrument. Within the limitations caused by the hard- and software of the system all parameters such as eluent concentration and flow rate, nebulizer and plasma gas flow, sampling frequency, integration time and the number of simultaneously measured emission lines were optimised. Further enhancement of the sensitivity was achieved by the use of an ultrasonic nebulizer pushing the detection limits down to the pg/g- and ng/g-range for 22 representative elements.Dedicated to Professor Dr. rer. nat. Dr. h. c. Hubertus Nickel on the occasion of his 65th birthday     

Investigation of the three-dimensional microstructure of Cu-Sn(Pb) diffusion zones by means of ion beam sputtering, scanning electron microscopy and lattice source interferences

On model substances of Cu-Sn(Pb) solders it is shown by the combined use of several physical analytical methods that the intermetallic compounds formed during the annealing process have a crystalline structure, which can be observed also three-dimensionally by ion etching. Moreover, grain boundaries as well as phases become visible, and it is possible to determine the crystallographic orientation of the individual crystals in the Cu starting material and in the diffusion zones by means of the Kossel technique. As a result of the investigations, conclusions can be drawn with respect to the diffusion process, especially also to the crystallographic structure of the diffusion zones and the dendritic growth.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

The effects of steric aliphatic–aliphatic interactions in the coordination polymer of bis(N,N-diethylglycinato)copper(II): Experimental evidence and theoretical modeling

New coordination polymer catena-poly[(N,N-diethylglycinato-κO,κN)copper(II)-μ-[N,N-diethylglycinato-κO¹,κN:O²]] has been obtained by single-crystal X-ray diffraction. The copper(II) was surrounded with two amino N and two carboxyl O atoms in trans position in the coordination plane. Discrete polymeric chains were produced by axial coordinative bonding between copper(II) and carbonyl oxygen atom from adjacent asymmetric unit. Molecular mechanics (MM) force field developed to study the properties of copper(II) amino acid complexes reproduced well intermolecular aliphatic–aliphatic interactions between ethyl chains and C–H?O hydrogen bonding. The relative unit cell volume reproduction was 0.3%. Theoretical conformational analysis showed that experimentally obtained conformer was not the most stable in vacuo. The calculations of the unit cell packings and intermolecular interactions for a series of conformers elucidated the reasons that governed the experimentally obtained conformer to appear in the real crystal structure. MM results suggest that intermolecular aliphatic–aliphatic interactions between ethyl groups affected a conformational change concurrent with the change in the copper(II) coordination sphere upon crystallization.