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Suspended carbon nanotube field-effect transistors fabricated with a dry transfer technique demonstrate strong promise as ultra-low-power, hysteresis-free gas sensors. However, the difficulty of establishing a good electrical contact between a nanotube and the electrode surface often limits the yield of low-resistance devices that can operate as low-power gas sensors. In this work, the contact resistance at the nanotube-metal interface and the distribution thereof are reduced significantly by removing the top layer of electrode surface with Ar-ion etching directly before nanotube placement. Combined with post-transfer annealing, this pre-transfer electrode surface cleaning reduces the median ON-resistance of transistors by an order of magnitude--from 1.56 MOhm to 143 kOhm--and the interquartile range by more than two orders of magnitude--from 9.38 MOhm to 59 kOhm. The ability to consistently improve nanotube-metal contact demonstrated in this work is a significant advance in the fabrication of ultraclean nanotube transistors and carbon nanotube gas sensors., Sensors and Actuators B: Chemical, 331

Monolithic, nitrogen-doped carbon sorbents were prepared from resorcinol-urea-formaldehyde resins and physically activated with CO2 for different activation times. The effect of the activation time on the water sorption behavior and the physicochemical properties were investigated. Longer activation times lead to a steeper slope of the water sorption isotherm and, due to a higher specific surface area and micropore volume, an increased water sorption capacity. It was found that, after physical activation for 3 h at 800 °C, the physically activated, nitrogen-doped carbon has a high surface area (>1000 m2/g) and a high water sorption capacity (50 wt%). In a miniaturized adsorption heat pump test stand, the best candidate material was assessed alongside commercial silica gel for reference. At a temperature swing from 90 °C → 50 °C, the CO2-activated carbon exhibits a maximal specific cooling power which is a factor of 1.7 higher in comparison with the reference silica gel (429 W/kg versus 255 W/kg). At a more applicable temperature swing, 60 °C → 30 °C, the CO2-activated carbon yields a specific cooling power 3.8 times higher than that of the silica gel reference (932 W/kg versus 240 W/kg).

Ceramic composite materials are increasingly used in dental restoration procedures, but current ceramic surface designs do not yet achieve the osseointegration potential of state-of-the-art titanium implants. Rapid bone tissue integration of an implant is greatly dependent on its surface characteristics, but the material properties of ceramic composite materials interfere with classical surface modification techniques. Here, ultra-short pulsed laser machining, which offers a defined energy input mitigating a heat-affected zone, is explored for surface modification of ceramic composites. Inspired by surface textures of clinically relevant titanium implants, dual roughness surfaces are laser patterned. Raman mapping reveals a negligible effect of ultra-short pulsed laser ablation on material properties, but a laser-induced change in the wetting state is revealed by static contact angle measurements. Laser patterning of surfaces also influences blood coagulation, but not the attachment and spreading of osteoblastic cells. The presented laser machining approach thus allows the introduction of a rational surface design on ceramic composites, holding great promise for the manufacturing of ceramic implants., Applied Surface Science, 545, ISSN:0169-4332, ISSN:1873-5584

This overview article on diamond-like carbon (DLC) coatings in medical applications covers the interaction of cells and tissue with DLC and alloyed DLC to generate desired cell reactions as well as the release of toxic elements. The promising in vitro results of DLC to prevent thrombus formation in vascular applications are summarized and the problems of transferring these results to in vivo applications are described. Since DLC shows extremely low wear in technical applications, a desired implementation is also to build wear particle free, articulating joint replacements by coating the bearing surfaces. Several in vivo studies using DLC coatings on articulating joints resulted in a failure due to partial coating delamination some years after implantation. It will be shown that this delayed delamination was caused by crevice corrosion (CC) of the adhesion-promoting interlayer and the reason why different corrosion processes may prevent an easy transfer of a successful technical application of DLC onto an implant will be discussed. The main issue for successful, long-term, in vivo applications of DLC coatings on implants is to predict the in vivo survival time and especially the long-term adhesion stability of the coating. The formation at the interface of a few atomic layers of reaction products, usually a metal-carbide, will be addressed. Furthermore, any contamination from residual gas or any cross contamination will result in a different reactively formed interface material with different properties. Delamination can then occur by a slowly advancing crack in this thin carbidic layer governed by the laws of stress corrosion cracking (SCC). It will be shown that if a stable coating adhesion is obtained, DLC coated articulating implants show basically no wear of the coating up to 101 million articulations on a simulator corresponding to about 101 years of in vivo articulation.

Advanced Functional Materials, 27 (8), ISSN:1616-3028, ISSN:1616-301X

CrystEngComm, 18, ISSN:1466-8033

The evolving usefulness of organic conducting polymers, of metallic or semiconducting type, is primarily dependent on their mechanisms of electrical conduction and degradation. Understanding these mechanisms is crucial for improving the effi ciency and lifetime of technologies derived from this class of polymers. There is demand for a model that provides a vivid and more precise evaluation of the electrical conduction mechanism in these polymers – especially when they act as hosts to guest species, such as acid dopant ions and nanoparticles. If, for example, the motional behavior of a host–guest organic conducting polymer structure, as related to dynamic stability, is either asynchronous or synchronous, is this refl ected in the mechanism of electrical conduction and does it account for the pace of material’s degradation? Here, we demonstrate that the answer is affi rmative: asynchronous structural motions arising due to loosely bound or free guest species within the host polymer lead to anomalous electrical conduction mechanisms, increased fragility and short lifetime, at odds with the synchronous behavior.

Results from a study conducted between National Metrology Institutes (NMIs) for the measurements of the absolute thicknesses of ultra-thin layers of SiO2 on Si are reported. These results are from a key comparison and associated pilot study under the auspices of the Consultative Committee for Amount of Substance. ‘Amount of substance’ may be expressed in many ways, and here the measurand is the thickness of the silicon oxide layers with nominal thicknesses in the range 1.5–8 nm on Si substrates, expressed as the thickness of SiO2. Separate samples were provided to each institute in containers that limited the carbonaceous contamination to approximately < 0.3 nm. The SiO2 samples were of ultra-thin on (100) and (111) orientated wafers of Si. The measurements from the laboratories which participated in the study were conducted using ellipsometry, neutron reflectivity, X-ray photoelectron spectroscopy or X-ray reflectivity, guided by the protocol developed in an earlier pilot study. A very minor correction was made in the different samples that each laboratory received. Where appropriate, method offset values attributed to the effects of contaminations, from the earlier pilot study, were subtracted. Values for the key comparison reference values (agreed best values from a Consultative Committee study) and their associated uncertainties for these samples are then made from the weighted means and the expanded weighted standard deviations of the means of these data. These results show a dramatic improvement on previous comparisons, leading to 95% uncertainties in the range 0.09–0.27 nm, equivalent to 0.4–1.0 monolayers over the 1.5–8.0 nm nominal thickness range studied. If the sample-to-sample uncertainty is reduced from its maximum estimate to the most likely value, these uncertainties reduce to 0.05–0.25 nm or ∼1.4% relative standard uncertainties. The best results achieve ∼1% relative standard uncertainty. It is concluded that XPS has now been made fully traceable to the SI, for ultra-thin thermal SiO2 on Si layers, by calibration using wavelength methods in an approach that may be extended to other material systems. © Crown copyright 2009. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.

Increasing use of DLC coatings in oil-lubricated, mechanical systems has led to a great deal of interest in optimising the interactions between lubricant additives and coatings. We have looked at the formation of a tribofilm from ZnDTP on diamond-like carbon (DLC) when sliding in oil against DLC on a polished steel substrate under very low wear conditions. It was found that the tribofilm formed in the absence of iron adhered very weakly to the surface and could be removed by washing in an ultrasonic bath. The wear was too low to be detected with laser profilometry. AFM imaging of the surfaces of steel and DLC after sliding of steel/steel and DLC/DLC showed that the tribofilm formed on DLC had a very different morphology to that formed on steel. EDX was used to demonstrate that the tribofilm contained zinc, sulphur and phosphorus. ToF-SIMS measurements showed that iron was neither present at the DLC surface nor in the tribofilm.

Focused ion beam physical sputtering and iodine-enhanced etching of indium phosphide (InP) were performed. Up to 15× enhanced etching rates over sputtering were measured at room temperature, due to the addition of iodine to the sputter-process. Reaction mechanisms and products are discussed and characterized. The reaction is limited by the desorption of indium triiodide (InI 3 ) at room temperature. InI 3 has to be removed by sputtering, which simultaneously amorphizes the underlying substrate. Surface roughness and stoichiometry of InP are compared for sputtering and etching. Gallium-contamination and the damaged zone in InP are significantly reduced by iodine-enhanced etching. Based on the reaction mechanisms, an optimum beam scanning strategy is proposed which allows precise microfabrication in reduced time and minimizes damage to the substrate. The method is also applicable for other halide gas etching processes of III–V semiconductors.

A study was carried out for the measurement of ultrathin SiO on (100) and (111) orientation silicon wafer in the thickness range 1.5-8 nm. XPS, medium-energy ion scattering spectrometry (MEIS), nuclear reaction analysis (NRA), RBS, elastic backscattering spectrometry (EBS), SIMS, ellipsometry, gazing-incidence x-ray reflectometry (GIXRR), neutron reflectometry and transmission electron microscopy (TEM) were used for the measurements. Water and carbonaceous contamination about 1 nm were observed by ellipsometry and adsorbed oxygen mainly from water at thickness of 0.5 nm were seen by MEIS, NRA, RBS and GIXRR. The different uncertainty of the techniques for the scaling constant were also discussed.

Diamond-like carbon (DLC) films are well known for their outstanding tribological properties, which has been shown in many studies. Because of their extreme hardness, low coefficient of sliding friction (often after some running-in time) and especially their ability to form a transfer layer on the counter-body of the frictional pair, these coatings have found different areas of application. There are many different types of these coatings on the market depending on the deposition process and on the deposition parameters used. The dependence of the film properties on the deposition conditions allows the tailoring of certain film properties to specific applications. Additionally, alloying with different elements allows further adaptations. A special tribological problem is found in applications where almost no or only little motion takes place and therefore no transfer layer can build up. In this case a special coating is needed which has a low coefficient of friction already at the very beginning of any motion. A similar situation is found in low-load applications where neither a transfer layer is created nor the transformation of the topmost surface layer into a more graphitic-like state takes place. In this study, silicon containing DLC films are produced in a RF plasma-activated chemical vapor deposition system. A mixture of acetylene and an organosilicon gas is used to deposit silicon containing DLC films onto hardened steel sample plates. On top of a supporting coating, a 30-nm thick DLC layer with varying silicon content is deposited using different selected self-bias voltages. The coefficient of static friction against a hardened stainless steel surface is then measured in dependence of the silicon content in the film and of the self-bias used during deposition. The films display a constant coefficient of static friction even after many single measurements. The results are compared to results obtained for pure DLC films.

Hydrogenated amorphous carbon films or diamond-like carbon films have shown their outstanding tribological properties in many studies and in many applications. This is due to their extreme hardness, low coefficient of sliding friction (after some running-in time) and especially, their property to form a transfer layer on the counter-body of the frictional pair. Hydrogenated amorphous carbon coatings describe a large class of different coatings with properties ranging from relatively soft to extremely hard, from highly amorphous to more graphitic-like and from high hydrogen contents to hydrogen free, as well as any combination of these. A special problem is found in applications, where almost no or only little motion takes place, because either the static friction cannot be overcome or the running-in cannot be completed, because the transfer layer cannot form. In all these cases, a special coating is needed, which has a low coefficient of friction, already at the very beginning of any motion. A similar situation is found in low load applications, where neither a transfer layer is created nor a transformation of the topmost surface layer into a more graphitic-like state takes place. Diamond-like carbon films in this study are produced in a r.f. plasma-activated chemical vapour deposition system from acetylene and deposited onto hardened steel plates. The coefficient of static friction against a hardened stainless steel surface is then measured in dependence of the self-bias, used for the topmost coating layer. Different measurement methods have been used to prove the reproducibility. It was furthermore shown that these films displayed a constant coefficient of static friction even after 200 single measurements. The overall average coefficient of static friction in air was 0.158±0.002, and in a dry nitrogen atmosphere 0.126±0.003 as compared to 0.210±0.011 for uncoated surfaces in air.

Metal-on-metal (MOM) hip joint bearings are considered one of the alternatives to the generally used metal-on-polyethylene bearings. In order to control and minimize wear of MOM bearings, an in-depth understanding of the acting wear mechanisms is essential. In a recent study it was suggested that layers of decomposed proteins are generated due to high pressures between contact spots of the cobalt–chromium alloy bearing. It was further suggested that these tribochemical reaction products greatly influence the wear behavior of the MOM articulation. Since these conclusions were limited to in-vitro test observations, the purpose of this study was to compare retrieved McKee–Farrar prostheses with the previously utilized in-vitro specimens to investigate tribochemical layer presence, composition and role in the overall wear process. Forty-two retrieved McKee–Farrar prostheses with a complete clinical record were compared to the in-vitro specimens. Ninety-three percent of the cups and 83% of the heads of the retrieval collection showed macroscopically and microscopically similar layers than the in-vitro bearings. SEM revealed a varying layer thickness with scratched or smeared sections. Combined SEM and EDS analysis suggested the presence of carbon and oxygen in most of the layers, while some layers showed traces of sodium, magnesium, calcium, nitrogen, sulfur, phosphorus and chlorine, too. These observations were quantitatively verified using XPS. By means of protein standards the organic origin of the layers was shown. Since the latter covered large areas of the contacting surfaces, adhesion is minimized and abrasion is reduced. Thus, the layers have a solid lubricating effect and the general wear behavior of the MOM bearing is affected by generation and delamination of the tribochemical reaction layers.

We study the protein adsorption on surfaces in order to investigate their predominant role in biocompatibility. Nanostructures are created by local anodic oxidation on titanium using the atomic force microscope. A remarkable specificity of the actin filament adsorption on the nanostructure height is noticed. F-actin is observed to have a low adsorption on nanostructures of a height of 4 nm and the adsorbed proteins appear to be randomly oriented. In contrast high protein adsorption is observed for structure height between 1 and 2 nm, moreover the filaments adsorb preferentially parallel to the nanostructured pattern.

Diamond-like carbon (DLC) has become one of the most widely used wear-protective low-friction coatings due to its outstanding mechanical and tribological properties. However, a major disadvantage of DLC is the deterioration of its lubricating properties at high relative humidity, limiting its use in certain tribological applications for which ambient humidity may be subject to significant variations. The addition of small amounts of Si to DLC has been reported as an effective method for reducing friction coefficient at high humidities. In this paper we have characterised the tribological behaviour of a reference DLC coating prepared using a PACVD technique in the relative humidity range 5–85%, sliding against steel, alumina and DLC counterfaces, and directly compared this to similar coatings alloyed with small amounts of Si (

Nowadays a variety of different hard coatings are commercially available, the most widely used ones are TiN, TiC, TiCN, TiAlN, CrN, Al 2 O 3 , and combinations thereof, as well as some coatings with lubricating properties such as diamond-like carbon (DLC), WC/C or MoS 2 . To fulfil the industrial demands for improved coatings, a lower friction, a longer lifetime, a desired biological behavior or a better thermal stability in different environments, improved and application adapted coatings are developed. The different properties of a coating can be tuned to a desired value by alloying with suitable elements. Composite materials such as multilayer coatings and isotropic nanocomposite coatings, having structures in the nanometer range, can even show properties which can not be obtained by a single coating material alone. The authors review research and development work on the improvement of the overall coating performance, It mainly addresses alloying, the development of multilayer systems and the recently emerged field of nanocomposite coatings.

The different properties of a-C:H can be tuned, either by alloying additional elements into the amorphous a-C:H or by building multilayer structures composed of two different types of a-C:H. This allows the design of optimized coatings for a wide range of applications. Multilayered a-C:H films, composed of a 60 nm Si-a-C:H adhesion layer and 300 nm multilayer structure have been deposited by a periodical variation of the sample self-bias voltage during deposition. The single layer thickness has been varied from 4 to 20 nm. The wear rate (determined by pin-on-disk measurement against a steel ball) of multilayer structures having a single layer thickness in the range of 12–14 nm, showed a drastic decrease by one decade down to 4×10 −18 m 3 Nm −1 , compared to the multilayer systems composed of thicker or thinner single layers. Amorphous hydrogenated carbon films containing titanium in different concentrations (a-C:H/Ti) were deposited by a combined RF-PACVD and DC magnetron sputtering process. The titanium content in the carbon matrix caused cellular reactions of bone marrow cells (BMC) like enhanced cell proliferation together with a reduced osteoclast cell activity. This could make a-C:H/Ti a valuable hard coating for bone implants, by enhancing bone ingrowth through osteoblast differentiation while reducing bone resorption through osteoclast inhibition.

Amorphous hydrogenated carbon films (a-C : H) containing different amounts of Ti or V were produced by combined plasma-activated chemical vapour deposition and d.c. magnetron sputtering. New bioactive materials resulted from the combination of the excellent tribological and biological properties of the a-C : H matrix with the biological response to the incorporated metals. By adding Ti to the a-C : H matrix, an enhanced differentiation of osteoblast- and reduced osteoclast-like cell activity was achieved, leading to a coating that is valuable for bone implants: enhancing bone ingrowth through increased osteoblast activity and reducing bone resorption through osteoclast-like cell inhibition. The a-C : H/V films reduced lysosomal activity as well as neutral red uptake in bone marrow cell cultures, thus being an interesting coating for short-term implants where reduced cell attachment is required. Prior to cell culture tests, the surfaces of the metal-containing a-C : H films were investigated by x-ray photoelectron spectroscopy. The relation between chemical surface composition and cellular response is discussed.

A new microelectrode is presented, based on an electrochemically etched Pt/Ir needle with a high aspect ratio and a radius of curvature smaller than 1 μm. The needle is electrically insulated by a thin (15 to 20 nm) insulation film made of hydrogenated amorphous carbon (a-C:H). In order to use the needle as a microelectrode, the very end is made conductive again through a local oxygen plasma. The localization of the plasma is achieved in a specially designed scanning tunneling microscope (STM) working in a high pressure oxygen atmosphere. The reduction of the total resistance after the local plasma treatment was proved by measuring the transition resistance between the needle and a 0.1 M NaCl solution. It is supposed that the two processes responsible for the decrease of the resistance are: (a) the reduction of the thickness of the a-C:H insulation by reactive oxygen ion etching, (b) transformation of the a-C:H film into a more graphitic-like state (increased content of sp2 bondings) by a thermal process. The functioning of this new type of electrode was tested by measuring the transmembrane potential of mouse liver cells in vitro.

Multilayer coatings of metallic (Au, Ni, Pb or PbO) and MoS 2 nanometer-scale layers were deposited by r.f. magnetron sputtering on 440C steel with a Cr adhesion layer. The structure, composition and thickness of the multilayers were studied by Rutherford back-scattering (RBS) and X-ray diffraction (XRD) spectroscopies. Pin-on-disk tribometer tests were performed in humid air of 50% RH. In order to investigate chemical and mechanical aspects of wear in humid air, the worn surfaces of the multilayers and of the counter parts were studied by scanning Auger microscopy (SAM) and scanning electron microscopy (SEM) after different sliding distances. The chemistry of wear was found to be associated with elimination of Mo from the contact surfaces. Relative to pure sputter-deposited MoS 2 coatings, lower values and more stable mean friction coefficients were observed for the metal–MoS 2 multilayers studied at higher loads. A correlation between the morphology and sliding properties of multilayers was found to be associated with an increased preferred basal orientation of MoS 2 in nanoscaled layers. The role of metal is most likely associated with a structural modification of MoS 2 rather than “gettering” of oxygen during sliding. It is concluded that the improvement in the tribological performance of sputter-deposited metal–MoS 2 multilayers in humid air can be generally attributed to the optimization of MoS 2 morphology in nanostructured multilayer coatings.

Nanoscaled multilayer coatings consisting of alternating layers of hard and soft amorphous hydrogenated carbon (a-C:H) films have been deposited by modulation of the substrate bias voltage in a plasma activated chemical vapor deposition (PACVD) process. Alternating hard/ soft a-C:H nanolayers is a model system to investigate the correlation of the different layers and interfaces with the final tribological and mechanical properties. The substrate bias voltage determines the ratio of sp2/sp2 bonded carbon, the internal stress and the hydrogen content in the different a-C:H layers, all of which contribute to the mechanical properties. Different bias voltage functions (sinusoidal, triangular, rectangular, etc.) were used to obtain soft, graded or sharp interfaces between the layers. The mechanical and tribological behavior of the multilayer structures have been characterized by tribological tests.

Pure TiN and MoSX, as well as Au/TiN, Ti/TiN and MoSX/Pb multilayers (multilayer layer thickness 4–50 nm), have been prepared by magnetron sputtering at room temperature. The characteristics of these films have been investigated using atomic force microscopy, X-ray diffraction and reflection, Auger depth profiling and Rutherford backscattering. The wear properties of the films have been determined using pin-on-disc measurements and the hardness of the films have been examined using nanoindentation techniques. Results show that the mechanical properties depend on multilayer thickness and that oxygen contamination from the background vacuum result in a degradation of film performance.

We report successful introduction of negatively charged nitrogen-vacancy (NV(-)) centers in a 5 nm thin, isotopically enriched ([(12)C] = 99.99%) diamond layer by CVD. The present method allows for the formation of NV(-) in such a thin layer even when the surface is terminated by hydrogen atoms. NV(-) centers are found to have spin coherence times of between T2 ~ 10-100 μs at room temperature. Changing the surface termination to oxygen or fluorine leads to a slight increase in the NV(-) density, but not to any significant change in T2. The minimum detectable magnetic field estimated by this T2 is 3 nT after 100 s of averaging, which would be sufficient for the detection of nuclear magnetic fields exerted by a single proton. We demonstrate the suitability for nanoscale NMR by measuring the fluctuating field from ~10(4) proton nuclei placed on top of the 5 nm diamond film.

Amorphous hydrogenated carbon films are of high technological interest as protection coatings owing to their special properties such as high hardness, chemical inertness, and infrared transparency. However, the applications are restricted owing to the poor thermal stability of these coatings. Fluorinated amorphous hydrogenated carbon (a-C:H:F) films are produced by r.f. plasma deposition from a mixture of acetylene and trifluoromethane with a self bias of −300 V. The structural changes upon annealing in an argon atmosphere of films with fluorine concentrations varying from 0.1% to 20% are investigated. Raman spectra were measured on each film for different annealing temperatures. The spectra are decomposed into single Gaussians and the ratio of the intensities of the D peaks to the G peaks is used as a measure of the transition from the amorphous structure to the more graphitic-like structure. This transition temperature can be used as an indication of the structural stability of these films upon annealing. The transition temperature versus the fluorine concentration is found to decrease for increasing fluorine concentration, showing, therefore, a decreasing temperature stability upon fluorination. Furthermore, this decrease shows a linear dependence on the fluorine concentration.

Thin TiO 2 films were grown with a new solid titanium pyrazolylborate precursor by thermal metal organic chemical vapour deposition (MOCVD) in a temperature range of 300–800°C. Previous differential thermal analysis/thermogravimetric measurements have shown that this precursor is suitable for reduced pressure MOCVD systems. The amorphous character of the films deposited on quartz, sapphire, and Si [1 0 0] substrates was proven by X-ray diffraction. Oxygen and ammonia were used as reaction gases.

X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used to study the influence of fluorine contamination on aluminium microchip bond pads. Sputter depth profiles indicated that the oxide layer thickness on those band pads, which showed poor gold wire adhesion, was higher than the thickness of the native oxide layer of aluminium. This corrosion was induced by segregation of fluorine into the bulk during storage of the wafers in closed polypropylene boxes. The contamination was found to be of the Al(OF)x type, which was initially formed in the CF4/O2 plasma-etching process. On test samples of aluminium metallization that have been stored with the process wafers, the fluorine contamination was located on the surface only. No segregation and no further oxidation occurred. In this case the fluorine contamination is of the AlFx type.

Intermetallic Ni 3 Al thin layers and Ni 3 Al/Ni multilayers were deposited on a Si wafer by means of magnetron sputtering. The structure and morphology of the layers have been characterized by X-ray diffraction, transmission electron microscopy and atomic force microscopy. The polycrystalline films are textured in the (111) direction and have grain sizes below 20 nm. Superlattice reflections due to chemical order have been observed in the electron microscope. It is shown by x-ray diffraction that the multilayers grow coherently on the amorphous substrate.

For nonmagnetic disordered metals Nagel and Tauc have proposed an electronic influence on stability due to an electron-mediated indirect interaction between the ions. This interaction causes a structure-induced minimum in the electronic density of states and electronic-induced structure properties. In the present paper we show indications for another influence, electron-mediated as well, due to indirect magnetic interaction between local moments. Interrelations between electronic and structural properties and their influence on stability and magnetic properties are shown for FexX1−x metallic glasses (X: Sn, Ge, Sb).

Bimetallic Pd-Au and Pt-Au and monometallic Pd, Pt, and Au films were prepared by physical vapor deposition. The resulting surfaces were characterized by means of XPS, AFM, and CO adsorption from the liquid phase (CH2Cl2) monitored by ATR-IR spectroscopy. CO adsorption combined with ATR-IR proved to be a very sensitive method for probing the degree of interdiffusion occurring at the interfaces whose properties were altered by variation of the Pd and Pt film thickness from 0.2 to 2 nm. Because no CO adsorption was observed on Au, the evaporation of Pt-group metals on Au allowed us to study the effect of dilution on the adsorption properties of the surfaces. At equivalent Pd film thickness, the evaporation of Au reduced the amount of adsorbed CO and caused the formation of 2-fold bridging CO, which was almost absent in monometallic surfaces. Additionally, the average particle size on Pd-Au surfaces was smaller than that on monometallic Pd surfaces. The results indicate that a Pd/Au diffuse interface is formed that affects the Pd particle size even more drastically than the simple decrease in Pd film thickness in monometallic surfaces. Pt-Au surfaces were less sensitive to CO adsorption, indicating that the two metals do not mix to a significant extent. The difference in the interfacial behavior of Pd and Pt in the bimetallic gold films is traced to the largely different Pd-Au and Pt-Au miscibility gaps.

The copper precursors bis-hexafluoroacetylacetonato-copper Cu ~hfac) 2 , vinyl-trimethyl-silane-copper~I!-hexafluoroacetylacetonate ~hfac!Cu~VTMS!, 2-methyl-1-hexen-3-yne-copper-hexafluoroacetylacetonate ~hfac!Cu~MHY!, and dimethylbutene-copper~I!-hexafluoroacetylacetonate ~hfac!Cu~DMB! are compared with respect to deposition rates and metal content obtained by focused electron beam induced deposition. Exposure was performed with 25 keV electrons in a Cambridge S100 scanning electron microscope equipped with a lithography system. Tip deposition rates increase with increasing precursor vapor pressure and range between 47 nm/s for ~hfac!Cu~DMB! to about 4 nm/s for Cu~hfac) 2 . A decay of deposition rates with time, i.e., tip length, is observed. Electric 4-point measurements indicate an insulating behavior of deposited lines for all precursors. In contrast, Cu contents of up to 45-60 atom % were found by Auger electron spectroscopy in thin rectangular deposits using ~hfac!Cu~DMB! and ~hfac!Cu~VTMS! as precursors. A discussion in terms of monolayer coverage, completeness of precursor molecule dissociation, and precursor stability is presented.

We present a photoemission study of the CO adsorption on amorphous Ni-Zr alloys at various compositions. Our results indicate a distinct enhancement of dissociative adsorption even at very low Zr concentrations. These observations are supported by LCAO-type calculations of potential energy surfaces, which suggest a strong increase of backdonation into antibonding CO 2π∗ type orbitals near Zr sites.

57Fe Mossbauer and photoemission measurements were performed on meltquenched amorphous Fe(Zr, B) and (Fe, Ni)B alloys. The atomic and electronic structure of Fe90Zr10 and Fe88B12 glasses were found to be different. Half of the Zr content could be replaced by B in the Fe90Zr10 glass without changing its structure. Mossbauer investigation of the amorphous (Fe1−xNix)100−yBy (0

In the present interlaboratory comparison, the consistency and validity of the Shirley, straight-line and Tougaard methods for determination of peak intensities from measured XPS spectra have been studied by analysis of data on Au and Ni taken at eight laboratories. The reproducibility of the individual measuring systems was determined to be 2–6%. The RMS scatter around their mean values of the ratio of the peak intensity to the Au 4d peak intensity was 6% for the Tougaard method, 9–10% for the Shirley method and 8–9% for the straight-line method. The increase in root mean square (RMS) scatter of data due to data being recorded in different laboratories amounts to 3–4%, independent of the method applied for background correction. The RMS deviation from theory of intensity ratios of peaks from Ni and Au to the Au 4d peak intensity is 14% for the Tougaard method, 33% for the Shirley method and 31% for the straight-line method. The absolute accuracy of the methods cannot be established to better than the accuracy on the theoretical peak intensity ratios and the uncertainty in the energy dependence of the analyser response function. It is, however, reasonable to expect the combined uncertainty of these factors to be at least 10–15%. The peak intensity ratios obtained with the Tougaard method then falls within the expected accuracy of the theoretical ratios.

The interface between diamond-like amorphous hydrogenated carbon (a-C : H) and Al2O3 was analysed by sputter depth profile analysis via x-ray photoelectron spectroscopy. X-ray photoelectron spectra were also recorded during direct ion beam deposition (CH4, E = 400 eV) monitoring the initial build-up of the interface. No stoichiometric interface compound was detected, although Al2O3 is reduced to Al2O3-x (x ∼ 0.5–1) enabling an interaction with the carbon atoms. This results in an excellent adhesion of a-C : H to the chemically inert Al2O3.

The original state of the interface between ultrahard amorphous hydrogenated carbon (a-C : H) and aluminum was analyzed by non-destructive in-situ direct ion beam deposition (CH 4 , −400 V) as well as angle resolved XPS (X-ray photoelectron spectroscopy) analysis through a thin a-C : H coating. Depending on the deposition conditions a 0.6 to 1.9 nm thick Al 4 C 3 interlayer, held responsible for the good adhesion between a-C : H and Al, could clearly be resolved. Furthermore, an interaction between a-C:H and Al 4 C 3 at the a-C : H/Al 4 C 3 interface was detected. The ability of C and Al to form a reactive Al 4 C 3 interface as well as an interaction of a-C : H with Al 4 C 3 has also been confirmed by XPS and AES sputter depth profile analysis.

The near normal incidence reflectivity of the ferromagnets U 3 P 4 and U 3 As 4 and the isostructural but diamagnetic compounds Th 3 P 4 and Th 3 As 4 has been measured from 0.03 to 12 eV. Trithorium tetraphosphide and tetraarsenide are shown to be indirect gap semiconductors with gap energies of 0.43 and 0.39 eV, respectively. U 3 P 4 and U 3 As 4 display similar sets of p→d transitions than the corresponding thorium compounds, however, they are shifted by 0.85 eV to lower photon energies. It is concluded that the uranium compounds are metals due to a merging of the valence p band into the 6d conduction band giving direct experimental evidence for a p-f mixing effect of the same size. Energy level schemes are derived.

Silicon (Si) based implantable components are widely used to restore functionalities in the human body. However, there have been reported instances of Si corroding after only a few years of implantation. A key parameter often overlooked when assessing Si stability in-vitro, is the added constricting geometries introduced through in-vivo implantation. The influence of crevices and confined solutions on the stability of Si is presented in this study, considering two simulated physiological solutions: 0.01 M phosphate buffered saline (PBS) and HyClone Wear Test Fluid (WTF). It was found that Si is highly vulnerable to corrosion in confined/crevice conditions. High pitting corrosion susceptibility is found in a crevice, whereas a dissolution rate of ca. 3.6 nm/h at body temperature occurred due to local alkalization within a confined cathodic area. The corrosion rates could be increased by elevating the temperature and yielded linear Arrhenius relations, with activation energies of 106 KJ/mol in 0.01MPBS and 109 KJ/mol in HyClone WTF, corresponding to a phosphorous-silicon interaction mechanism. Phosphorous species favored corrosion and contributed to enhanced Si dissolution, while chlorides were not so influential, and applied anodic potential induced pseudo-passivation. These results highlight the importance geometrical configurations can have on a material's surface stability. (c) The Author(s) 2019. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.

In the present study, the adsorption behaviour of H2O on an amorphous alloy has been investigated by photoemission experiments using glassy Ni64Zr36 and the polycrystalline references nickel and zirconium. With ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS), we have found mainly three different adsorption states on the substrates. On polycrystalline nickel, water is adsorbed molecularly at 100 K even at very low coverages while on Zr the first layer is dissociated into adsorbed oxygen (Oads) and hydrogen (Hads) and/or (OH)ads and Hads. On the metallic glass the formation of OHδ− groups is favoured. The experiment clearly demonstrates that the combination of an early transition metal (Zr) with a late transition metal (Ni) leads to an adsorption behavior which is not a superposition of those of the constituents. The results are compared to the adsorption of carbon monoxide (CO).

The carbon/silicon interface has been investigated by photoelectron spectroscopy comparing two different depth profiling techniques. While the nondestructive angle-resolved photoelectron spectroscopy on thermally evaporated carbon on silicon shows no interface reactions, the same sample analyzed by standard sputter depth profiling revealed a pronounced interface consisting of a silicon carbide compound. The formation of SiC is found to be caused by the impinging energetic ions during sputtering.

The chemisorption of CO molecules on NiZr metallic glasses has been studied by ultraviolet photoelectron spectroscopy (UPS) as a function of CO exposure, temperature, and alloy concentration. Molecular and/or dissociative CO chemisorption has been observed. The relevance of the local electronic properties of the substrate surfaces for the chemisorption mechanism is shown and a correlation between the Ni-3d band of the alloys and the CO molecule orbitals is reported for the first time.

The aim of this work is to investigate the influence of surface precleaning procedures prior to deposition of hydrogenated amorphous carbon films onto stainless steel. In industrial coating processes the substrates are first degreased and then Ar-ion sputter-cleaned in the deposition chamber just prior to film deposition. This sputter cleaning, which removes the native surface oxide layer as well as unknown contaminations, is carried out rather thoroughly to assure a good adhesion of the hard carbon film. In these films holes or pores are found when inspected with the scanning electron microscope. We demonstrate that these are not pores in the coating but holes in the stainless steel substrate at locations of manganese-sulphur inclusions. They are produced during the sputter-cleaning procedure owing to a higher sputter yield of the manganese-sulphur inclusions with respect to the stainless steel substrate. By carefully selecting the surface preparation procedures, the depth of these holes may be reduced below the surface roughness and can then be neglected. We also show that the Ar-ion sputter etching increases the surface roughness by less than 2% of the thickness of the removed layer and that the amorphous carbon film growth is extremely uniform, the increase in surface roughness being less than 1% of the film thickness for 100 nm thick coatings.

The STM has been used to study the morphologies and nanostructures of splat-cooled and laser-quenched Nb40Ni60 alloys. The experiments are performed under ultra high vacuum at room temperature. On Ar+ ion etched splats, islands 10–20 A in diameter with a maximum corrugation of 4 A can be observed. Atomic-scale features of 3–4 A have been observed. In a few cases nanostructures 30–50 A which contain a fine structure of 3 A dimension are found. These nanostructures could be assigned as nanocrystallites. Laser quenching of amorphous splats results in the formation of distinctly different surface morphologies, also on the scale of 20–30 A and around 10 A in height. The STM has been shown to be an effective tool for characterizing surface structures in amorphous metals.

The chemisorption of carbon monoxide on amorphous and crystalline alloys such as Pd-Si, NiZr, IrSi, and PdUSi has been studied by ultraviolet photoelectron spectroscopy (UPS). Systematic trends in the CO chemisorption behavior have been found for the various alloy systems. A correlation between the position of the valence band d-electron states of the LTM (late transition metals) and the molecular orbitals of the chemisorbed CO molecules is reported. The influence of the substrate electron states on the C-O bond strength is explained in a qualitative model involving the symmetry and the binding energy of the substrate valence electrons and those of the molecular orbitals.