Auger Analysis Research Articles

Structure and superconducting characteristics of magnesium diboride, substitution of boron atoms by oxygen and carbon

An x-ray analysis of MgB2-based materials shows that they contain MgB2 and MgO phases. According to a quantitative Auger analysis (taken after removing the oxidized surface layer by Ar ion etching in the microscope chamber) the MgB2 phase contains some amount of oxygen that approximately corresponds to the composition MgB2.2-1.7O0.4-0.6. Rietveld refinement of the MgB2 phase, based on EDX data with varying B/O content, leads to the composition MgB1.68-1.8O0.2-0.32. Ab-initio modelling of boron substitution by oxygen in MgB2 (ΔHf = −150.6 meV/atom) shows that this is energetically favourable up to the composition MgB1.75O0.25 (ΔHf = −191.4 meV/atom). In contrast to carbon substitution, where very small levels of doping can dramatically affect the superconducting characteristics of the material with concomitant changes in the electron density, oxygen substitution results in very little change in the superconducting properties of MgB2. The formation of vacancies at the Mg site of both MgB2 and substituted MgB1.75O0.25 was modelled as well, but has shown that such processes are energetically disadvantageous (ΔHf of Mg0.875B2 and Mg0.75B1.75O0.25 are equal to −45.5 and −93.5 meV/atom, respectively).

The use of AES and EELS for complex analysis of two-dimensional coatings and their growth process

Additional possibilities for complex analysis of two-dimensional coatings (thickness <1nm or <10ML) grown by physical vapor deposition (PVD) on a single-crystal silicon substrate under two deposition regimes have been revealed: 1) low-temperature (at a low beam temperature) and 2) high-temperature (at an elevated temperature of the beam), respectively. Coatings, including those in the form of pure metal and a silicide mixture, and their interface with the substrate have been analyzed by Auger electron spectroscopy (AES) and characteristic electron energy loss spectroscopy (EELS). A technology of the deposition from a ribboned source has been developed to ensure both deposition regimes. The conventional uses of AES are limited to the characterization of elemental composition, electron energy structure and coating thickness. For EELS, the conventional uses are the determination of phase types (valence electron density) and phase formation stages. The simultaneous use of the two methods and the choice of equal (and minimal) probing depths, ~ 2.5nm (primary electron energy 300eV), provided new possibilities for studying subnanometric two-dimensional coatings, in particular, for comparison of coating composition and density. The chosen probing depth also made it possible to characterize the interface between the coating and the substrate. At the same time, the use of similar probing depths made allowed using the thickness of the coating obtained from AES data for analyzing EELS data. In addition, other possibilities have been considered, i.e., the use of the following dependences: a) the energy of the plasmon satellite of the Auger peak vs the thickness of the coating for analyzing changes in the electron density in the near-interface layer of silicon; b) the attenuation of the Auger signal generated by marker atoms at the interface between the coating and the substrate for localizing the adsorption sites of the deposited atoms; c) the intensity and energy of the loss peaks in the EELS as a function of the primary electron energy for depth profiling of coating compositions. The use of two depth attenuation functions for two probing depths has enabled a quantitative Auger analysis of binary coatings. These advantages have provided the possibility of a more complete characterization of two-dimensional coatings and their interfaces with substrates, as well as the coating formation processes. In particular, it has for the first time become possible to identify the wetting nanophase layer of metals on silicon substrates, to investigate the process of its formation and to show how its composition depends on vapor-phase physical deposition modes.

The use of AES and EELS for complex analysis of two-dimensional coatings and their growth process

Additional possibilities for complex analysis of two-dimensional coatings (thickness &lt;1 nm or &lt;10 ML) grown by physical vapor deposition (PVD) on a single-crystal silicon substrate under two deposition regimes are revealed: 1) low-temperature (at low beam temperature) and 2) high-temperature (at an elevated temperature of the beam), respectively. Coatings, including in the form of pure metal and a silicide mixture, and their interface with the substrate were analyzed by Auger electron spectroscopy (AES) and characteristic electron energy loss spectroscopy (EELS). To ensure both deposition regimes, a technology of the deposition from the ribboned source was developed. The traditional use of AES is limited to determining the composition of the elements, the energy electronic structure, and the thickness of the coating. And EELS — the types of phases (the density of valence electrons) and the stages of their formation. The simultaneous use of both methods and the choice of equal (and minimal) probing depths, ~ 2.5 nm (primary electron energy 300 eV), provided new possibilities for studying subnanometric two-dimensional coatings, in particular, — for comparison of the composition of coatings and their density. The chosen probing depth made it possible to characterize also interface between coating and substrate. At the same time, the same probing depth made it possible to use the thickness of the coating obtained from the AES data to analyze the data of the EELS. In addition, other possibilities are considered. This is the use of dependencies: a) the energy of the plasmon satellite of Auger peak, depending on the thickness of the coating, for analyzing changes in the electron density in the near-interface layer of silicon; B) attenuation of the Auger signal generated by marker atoms at the interface between the coating and the substrate to localize the places of adsorption of deposited atoms; and c) the intensity and energy of the loss peaks in the EELS in dependence on the primary-electron energy for profiling the composition of coatings over the depth. The use of two attenuation functions for two depths of probing provided a quantitative Auger analysis of binary coatings. All this made it possible to characterize more fully both the two-dimensional coatings themselves and the interface layer of the substrate, as well as the processes of their formation. And, in particular, this made it possible to identify for the first time the wetting nanophase layer of metal on a silicon substrate, to investigate the process of its formation and to show how its composition depends on the modes of vapor-phase physical deposition.

The role of the nitrogen flow rate on the transport properties of CrN thin films produced by DC magnetron sputtering

Thin films of CrN were synthesized in a DC magnetron sputtering system using a mixture of Ar+N2. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS) revealing CrN bonds. The stoichiometry variation dependence on the N2 flow was also analyzed using Auger spectroscopy. Both, The XPS and Auger analyses were performed in situ. A gradual increase was observed in the nitrogen concentration in the coatings as the N2 was increased into the reaction chamber. The electrical behavior was studied while varying the N2 concentration. A lower resistivity was observed as the nitrogen concentration was increased into the sample before reaching the stoichiometric concentration; however, the resistivity increased at higher nitrogen concentrations (overstoichiometric coatings). Considering that chromium is a magnetic material, a slope change in the resistivity was observed around the Néel temperature. Furthermore, the obtained Hall coefficient showed changes in the carrier type (negative or positive) depending on the nitrogen concentration of the CrN coatings.

Matrix coatings based on anodic alumina with carbon nanostructures in the pores

The nanoporous anodic alumina matrixes thickness of 1.5mm and pore sizes of 45, 90 and 145nm were formed on Si substrates. The tubular carbon nanostructures were synthesized into the matrixes pores by pyrolysis of fluid hydrocarbon xylene with 1% ferrocene. The structure and composition of the matrix coatings were examined by scanning electron microscopy, Auger analysis and Raman spectroscopy. The carbon nanostructures completely filled the pores of templates and uniformly covered the tops. The structure of carbon nanostructures corresponded to the structure of multiwall carbon nanotubes. Investigations of mechanical and tribological properties of nanostructured oxide-carbon composite performed by scratching and nanoindentation showed nonlinear dependencies of the frictional force, penetration depth of the cantilever, hardness and plane strain modulus on the load. It was found that the microhardness of the samples increases with reduced of alumina pore diameter, and the penetration depth of the cantilever into the film grows with carbon nanostructures size. The results showed the high mechanical strength of nanostructured oxide-carbon composite.

Nanoscale Chemical Characterization of Solid-State Microbattery Stacks by Means of Auger Spectroscopy and Ion-Milling Cross Section Preparation.

The current sustained demand for "smart" and connected devices has created a need for more miniaturized power sources, hence for microbatteries. Lithium-ion or "lithium-free" all-solid-state thin-film batteries are adapted solutions to this issue. The capability to carry out spatially resolved chemical analysis is fundamental for the understanding of the operation in an all-solid-state microbattery. Classically cumbersome and not straightforward techniques as TEM/STEM/EELS and FIB preparation methods could be used to address this issue. The challenge in this work is to make the characterization of Li-based material possible by coupling ion-milling cross section preparation method and AES techniques to characterize the behavior of a LiCoO2 positive electrode in an all solid state microbattery. The surface chemistry of LiCoO2 has been studied before and after LiPON deposition. Modifications of the chemical environments characteristic of the positive electrode have been reported at different steps of the electrochemical process. An original qualitative and a semiquantitative analysis has been used in this work with the peak deconvolution method based on real, certified reference spectra to better understand the lithiation/delithiation process. This original coupling has demonstrated that a full study of the pristine, cycled, and post mortem positive electrode in a microbattery is also possible. The ion-milling preparation method allows access to a large area, and the resolution of Auger analysis is highly resolved in energy to separate the lithium and the cobalt signals in an accurate way.

Corrosion and Stress Corrosion Cracking Susceptibility of Type 347H Stainless Steel in Supercritical Water

The corrosion resistance and stress corrosion cracking (SCC) susceptibility of Type 347H stainless steel (SS) in supercritical water (SCW) were investigated. The general corrosion behavior was investigated by exposure test and the specimens after testing were characterized utilizing scanning electron microscopy (SEM), Auger and x-ray diffraction analysis, optical microscopy, and energy dispersive spectroscopy (EDS). The results show that with the increase of testing temperature, the corrosion rate of the materials is greatly enhanced. The corrosion process is analyzed and the formation of oxide islands on the surface of the corroded sample is attributed to the higher diffusion rate of Cr along the grain boundary. The effects of temperature and dissolved oxygen on SCC susceptibility were investigated by slow strain rate tensile test. The fractographs were characterized by SEM and the cross-section morphologies were characterized with back-scattered electron imaging, SEM, and EDS. The results indicate that, as temperature is increased, the tensile strength and strain of materials is greatly reduced, while the oxygen content in SCW has a limited effect on the mechanical properties. Intergranular cracking and ductile fracture are the main fracture modes for Type 347H SS tested in SCW, independent of temperature and oxygen content. The implications of the results to the mechanisms of SCC are discussed.

Structure and Properties of MgB2Bulks, Thin Films, and Wires

This paper describes the established correlations between the characteristics of MgB2-based superconducting materials and their structural features, in particular the oxygen distribution and content. As indicated by SEM and Auger analysis, a sizeable amount of oxygen is usually present in superconducting MgB2 -based materials (bulks, thin films, and wires). The matrix phase of bulk MgB2 contains rather small amounts of oxygen, but contains a high amount of dispersed inclusions or areas with compositions close to MgBO. X-ray phase analysis with Rietveld refinement (using the FullProf Suite program package) of several highly dense MgB2 -based bulk samples (with high critical current densities) showed that the superconducting phase had a composition within the range MgB1.68O0.26 and MgB1.74O0.32 instead of pure MgB2 . Besides, a small amount of a phase with MgO structure was observed in the materials by X-rays as well. The calculation of the enthalpy of formation confirms the possibility of oxygen solubility in MgB2 and shows that the formation of MgB1.75B0.25 is most favorable. The results of ab initio calculations of the electronic structure and stability of the MgB2 compounds with partial oxygen substitution for boron show that it is energetically preferable for oxygen atoms to replace boron pairwise.

Graphene Microcapsule Arrays for Combinatorial Electron Microscopy and Spectroscopy in Liquids.

Atomic-scale thickness, molecular impermeability, low atomic number, and mechanical strength make graphene an ideal electron-transparent membrane for material characterization in liquids and gases with scanning electron microscopy and spectroscopy. Here, we present a novel sample platform made of an array of thousands of identical isolated graphene-capped microchannels with high aspect ratio. A combination of a global wide field of view with high resolution local imaging of the array allows for high throughput in situ studies as well as for combinatorial screening of solutions, liquid interfaces, and immersed samples. We demonstrate the capabilities of this platform by studying a pure water sample in comparison with alkali halide solutions, a model electrochemical plating process, and beam-induced crystal growth in liquid electrolyte. Spectroscopic characterization of liquid interfaces and immersed objects with Auger and X-ray fluorescence analysis through the graphene membrane are also demonstrated.

Kinetics of Phosphorus Segregation in the Grain Boundaries of VVER-1000 Pressure Vessel Steels

Methods of AES quantitative analysis were developed and applied for the determination of element concentrations at the surfaces of brittle fractures along grain boundaries. An attempt was made to take into account the presence of carbide precipitates and cleavage areas in the zone of the Auger analysis of their impact on the results of quantitative measurements. Obtained data were used for evaluation of the phosphorous segregation kinetics. The obtained results are consistent with thermodynamic modeling with CALPHAD method.Kinetics of segregation is analyzed with three models: (1) Langmuir - McLean theory; (2) model akin to kinetics of first order chemical reactions in solids; and (3) the model, which takes into account contribution of fast transport within subgrain networks and slow diffusion through the grain bulk. The two later models are in a good agreement with the experimental results.

Synthesis and characterization of sulfur/carbon/porous nanostructured V2O5 composite cathodes for lithium sulfur batteries

Porous nanostructured V2O5 (PN-V2O5) was prepared by a facile spray pyrolysis and used as additive to synthesize sulfur/carbon/PN-V2O5 (S/C/PN-V2O5) composite by a combination of wet-ball-milling and heat treatment. The meso- and macropores in PN-V2O5 were confirmed by pore size distribution, which provided the favorable space to accommodate sulfur. The X-ray diffraction analysis showed that the crystal structures of S and V2O5 could be preserved below the heating temperature of 160°C and that high heating temperature (200°C) will result in reaction between S and V2O5. The pore size distribution curves of S/C/PN-V2O5 composites revealed that the penetrated S in PN-V2O5 pores mainly occupied the mesopores and macropores, which was further confirmed by a typical cross-sectional PN-V2O5 with Auger analysis. The S/C/PN-V2O5 composite cathode exhibited a discharge capacity of 632mAhg−1 after 60cycles at the current density of 100mAg−1 and the capacity retention of S/C/PN-V2O5 electrode was 27.3% higher than that of S/C electrode, demonstrating a better cycling performance.

Electronic and structural characterization of barrier-type amorphous aluminium oxide

The structural, electronic, and dielectric properties of barrier-type anodic Al oxides prepared with various thicknesses have been investigated. The planar and cross morphologies as well as the surface charge distribution were investigated as a function of the voltage applied during growth, i.e. the thickness. Three distinct anodizing potential domains can be clearly identified. A transition in ionic mobilities induces, at anodizing voltage higher than 100V, the built-up of space charge region in the anodic films.A correlated increased oxide density with growing anodization potential is consistently pointed out by Volta Potential Difference and XPS/Auger measurements.The full dielectric response of the oxides, including both the lattice and electronic components, has been accessed by electrochemical impedance spectroscopy and Auger analysis. The lattice contribution of the dielectric constant is found to be strongly affected by the growth voltage, as a clear increase in the lattice component of the dielectric constant is observed, reaching values close to those of bulk crystalline Al2O3 structures. At variance, the electronic contribution is only slightly affected. The results have been compared to dielectric constants calculated for atomistic amorphous models within the framework of density functional theory.It is shown that amorphous Al2O3 models of higher density lead to dielectric constants that could explain the trend observed in theseries of barrier-type anodic oxides prepared in this work.

Photoemission Fingerprints for Structural Identification of Titanium Dioxide Surfaces.

The wealth of properties of titanium dioxide relies on its various polymorphs and on their mixtures coupled with a sensitivity to crystallographic orientations. It is therefore pivotal to set out methods that allow surface structural identification. We demonstrate herein the ability of photoemission spectroscopy to provide Ti LMV (V = valence) Auger templates to quantitatively analyze TiO2 polymorphs. The Ti LMV decay reflects Ti 4sp-O 2p hybridizations that are intrinsic properties of TiO2 phases and orientations. Ti LMV templates collected on rutile (110), anatase (101), and (100) single crystals allow for the quantitative analysis of mixed nanosized powders, which bridges the gap between surfaces of reference and complex materials. As a test bed, the anatase/rutile P25 is studied both as received and during the anatase-to-rutile transformation upon annealing. The agreement with X-ray diffraction measurements proves the reliability of the Auger analysis and highlights its ability to detect surface orientations.

Formation of a Tribofilm in the Surface Layer of Al–Ti–Cr–N–B Magnetron Coating on Boron Nitride During Turning of Hardened Steel

The effect of cutting ShKh15 hardened steel on the element and phase composition of the surface layer of the coating deposited on the cBN-based tool is studied. The microstructure and oxidation kinetics of the surface layer of the AlN–Ti(Cr)B 2 magnetron coating are investigated during both formation and turning. The coating is formed by HF magnetron sputtering of an AlN–Ti(Cr)B 2 target. The formation of a two-layer tribofilm with a nanosize outer layer is examined. The phase composition of the tribofilm is determined using layer-by-layer Auger analysis. Its outer nanosize layer is a glass-like phase in the form of limited solid solutions based on Al 2 O 3 oxides and playing a role of solid lubricant. As the cutting speed is increased, the wear rate for the coated tool decreases compared with the uncoated tool.

Production and characterization of thin film group IIIB, IVB and rare earth hydrides by reactive evaporation

A recent short history of reactive evaporation by D. M. Mattox [History Corner—A Short History of Reactive Evaporation, SVC Bulletin (Society of Vacuum Coaters, Spring 2014), p. 50–51] describes various methods for producing oxides, nitrides, carbides, and some compounds, but hydrides were not mentioned. A study was performed in the mid-1970s at the General Electric Company Neutron Devices Department in Largo, FL, by the author to study preparation of thin film hydrides using reactive evaporation and to determine their unique characteristics and properties. Films were produced of scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), and the rare earth praseodymium (Pr), neodymium (Nd), gadolinium (Gd), dysprosium (Dy), and erbium (Er) hydrides by hot crucible filament and electron beam evaporation in atmospheres of deuterium and tritium gases. All-metal vacuum systems were used and those used with tritium were dedicated for this processing. Thin film test samples 1000 nm thick were prepared on 1.27 cm diameter molybdenum disk substrates for each occluder (i.e., an element that can react with hydrogen to form a hydride) material. Loading characteristics as determined by gas-to-metal atomic ratios, oxidation characteristics as determined by argon–sputter Auger analysis, film structure as determined by scanning electron microscope analysis, and film stress properties as determined by a double resonator technique were used to define properties of interest. Results showed hydrogen-to-metal atomic ratios varied from 1.5 to 2.0 with near maximum loading for all but Pr and Nd occluders which correlated with the oxidation levels observed, with all occluder oxidation levels being variable due to vacuum system internal processing conditions and the materials used. Surface oxide levels varied from ∼80 Å to over 1000 Å. For most films studied, results showed that a maximum loading ratio of near 2.0 and a minimum surface oxide level of ∼80 Å could be obtained with a bulk film oxygen level of ∼0.54 oxygen as determined by microprobe analysis when an evaporation rate of ∼0.313 mg/cm2 min was used in an atmosphere of D2 or T2 gas at a system deposition pressure of 1 × 10−3 Torr (1.33 × 10−1 Pa) in an evaporation time of ∼2 min. Platelet type (i.e., a film microstructure showing an overlay of flat plates with large grain sizes) film structures were observed for most films with some film mechanical properties determined (i.e., grain size and Vickers μ-hardness), and reduced stress levels were seen with initial normalized differential (tensile) stress levels being (1.0–4.0) × 108 dyne/cm2 for tritium loaded samples and (1.5 ± 0.5) × 109 dyne/cm2 for deuterium loaded samples. Also, stress aging characteristics were determined for some hydride films prepared in a radioactive tritium gas atmosphere. Tritium loading, however, had the undesirable characteristic of having to dispose of the internal processing system fixtures, which can be minimized, but the reactive evaporation technique produced desirable thin films.

Thin Oxide Film Reduction Via the Polyol Method: An Electrochemical Study of a Polyol Reduction Process

Polyols are non-aqueous hydrogen bonded liquids, analogous to alcohols, which have the ability to dissolve both organic and inorganic solids. Polyol synthesis [1] has been widely employed for the preparation of metallic nanoparticles using the temperature-dependent reducing ability of polyols in the presence/absence of capping agents, such as polyvinylpyrrolidone (PVP). In a typical polyol synthesis process, ethylene glycol (EG) is used as a solvent to dissolve metal precursors and as a mild reducing agent. By heating the mixture, the reducing power of the EG increases and ultimately reduces the metal precursors, forming metal nanoparticles with narrow-size distribution. In a modified-polyol method [2], an external reducing agent that is stronger than EG is used. This is usually practiced when the metal precursor can’t be reduced by the ethylene glycol alone. In a polyol or a modified polyol method, the metal precursor can be oxides, hydroxides, nitrates, and acetates that are either dissolved or suspended in the solvent. In case of oxide or hydroxide precursors, they have to be at least slightly soluble in EG at high temperature, otherwise, the addition of an acid is needed. In the work we are presenting here, we are investigating the possibility of using a (modified-)polyol method to reduce thin oxide films of solid surfaces and surface oxide of bulk oxide materials. We investigated the reduction of Sn oxide thin film [3] on a Sn metal substrate as well as the surface reduction of Sn oxide particles to produce meta-stable SnO2@Sn particles that spontaneously form stable SnO2@SnO particles once in contact with air. The reduction of the Sn oxide thin film on a Sn metal substrate was indicated by the sudden change in the Sn electrode potential when measured vs. a reference electrode (Ag/AgCl). Fig. 1 shows a typical OCP (open circuit potential) measured during heating and cooling cycles of hydrazine-containing ethylene glycol. The sudden change of the OCP at ~110°C is attributed to the reduction of the Sn oxide film as the interface changes from SnO2/EG to Sn/EG. More details about the origin of this OCP change will be provided in the presentation with the help of information obtained from quartz crystal microbalance (QCM) and/or impedance spectroscopy (EIS). The surface reduction of bulk Sn oxide in the form of SnO2 particles (50-100 nm) was also investigated. It was found that NaBH4 can reduce the surface oxide resulting in surface SnO. Raman spectroscopy showed that a very small amount of SnO was formed, which is reasonable if it was a surface oxide. Auger and XPS analyses did not show any SnO formation on the surface. The two pieces of information together suggest that SnO has formed on top of the SnO2, but due to the exposure to the atmosphere, the SnO on the top surface oxidized to SnO2 and therefore protected the remaining SnO underneath it and so it was detectable by the Raman and only SnO2 was found on the outermost surface. Further details and supporting results about the oxide reduction in both cases will be provided in the presentation. Acknowledgements The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2013-2016) for the Fuel Cell and Hydrogen Joint Technology Initiative under grant agreement CATAPULT n°.325268. Special thanks to Sebastian Schwaminger for the assistance with XPS and Raman analyses, Katia Rodewald for the superb SEM pictures and analyses and Marianne Hanzlik for the TEM analysis.

Reducing the aspect ratio of contact holes by in situ low-angle cross sectioning

Auger analysis of high-aspect ratio contact holes of integrated microelectronic devices is a challenging analytical task. Due to geometrical shadowing the primary electron beam and the energy analyser have not the required direct line of sight to the analysis area simultaneously. To solve this problem sample preparation is needed to flatten the three-dimensional geometry. Here the new approach of in situ low-angle cross sectioning is applied. By this method material gets removed inside the Auger instrument while the sample is sputtered by Ar+ ions at nearly grazing incidence utilizing the edge of a mask, which partly covers the sample. A very shallow bevel with respect to the sample surface is produced. Thus along the bevel contact holes with suitable aspect ratios are available for the Auger analysis.

Molecular beam epitaxy growth of niobium oxides by solid/liquid state oxygen source and lithium assisted metal-halide chemistry

In order to consistently grow high quality niobium oxides and lithium niobium oxides, a novel solid/liquid state oxygen source, LiClO4, has been implemented in a molecular beam epitaxy (MBE) system. LiClO4 is shown to decompose into both molecular and atomic oxygen upon heating. This allows oxidation rates similar to that of molecular oxygen but at a reduced overall beam flux, quantified by in situ Auger analysis. LiClO4 operation is decomposition limited to less than 400°C, and other material limitations are identified. The design of a custom near-ambient NbCl5 effusion cell is presented, which improves both short and long term stability. Films of Nb oxidation state +2, +3, and +5 are grown using these new tools, including the multi-functional sub-oxide LiNbO2.

AlN-(TiCr)B2 ion-plasma coating for cutting tools of cBN-based polycrystalline superhard material

The microstructure and oxidation kinetics of the surface layers of AlN-(TiCr)B2 coating produced by magnetron RF sputtering have been studied in the course of the coating formation and use in tools of cBN-based polycrystalline superhard materials in machining ShKh 15 hardened steel. The coating is formed with the liquid phase present. After cutting the formation of two-layer tribofilm with a nanosized external layer has been revealed on the surface of the cutting insert. The tribofilm phase composition has been defined by a layer-by-layer Auger analysis. The film external nanosized layer is a glassy phase as solid solutions of Fe2O3-Al2O3 oxides that acts as a solid lubricant. As the cutting speed increases, the wear rate of a tool with a coating has been found to decrease as compared with tools without a coating.

Nano-scale chemistry of self-assembled nanostructures in epitaxial SiGe growth

Epitaxial growth of SiGe alloy films under certain kinetically limiting conditions has previously been shown to lead to the self-assembly of nanostructures called Quantum Dot Molecules, QDMs. These QDMs consist of an assembly of pyramidal pits and elongated pyramidal islands, which exist at the edges of the pits. We investigate the nano-scale chemistry of QDMs in Si0.7Ge0.3/Si (100) using Auger electron spectroscopy (AES). First, our AES analysis indicates that compressively strained QDM pit bases are most Ge rich regions in QDMs, consistent with previously reported observations. Second, our Auger analysis of the QDMs shows that Ge composition continuously increases from outside edges of the islands to the pit cusps. This results in asymmetric distribution of Ge about the apex of the islands. The segregation of Ge to the pit cusps is unexpected on the basis of strain energy minimization, and we propose that it is due to attachment of Ge to steps on the interiors of the QDMs. The continually varying Ge composition towards the pit cusps is also inconsistent with previous observations of islands in GeSi growth, where the composition is reported to be symmetric about the apex of islands.