Showing papers in "Vacuum in 1999"
TL;DR: A review of the deposition of multilayered coatings by reactive sputtering and characterization of these coatings using transmission electron microscopy and X-ray diffraction is presented in this paper.
Abstract: Multilayer coatings with layer thicknesses in the nanometer range have been shown to exhibit extremely high hardnesses, making them useful as abrasion-resistant coatings. Hardness values in excess of 5000 kg/mm2 have been achieved in multilayers composed of two nitride materials, such as TiN and VN, with bilayer periods of 5–10 nm. This article begins with a review of the deposition of multilayered coatings by reactive sputtering and the characterization of these coatings by transmission electron microscopy and X-ray diffraction. The hardness enhancements observed in both isostructural and non-isostructural nanometer-scale multilayers are then reviewed. Several explanations for this enhancement in hardness have been developed in order to understand the hardening process and to develop coatings with even higher hardness. Models based on dislocation motion within layers and across layer interfaces, as well as Hall–Petch-type models, have successfully been applied to multilayers to explain this hardness enhancement, and they are briefly outlined.
TL;DR: In this article, a thin film (∼1.5μm) of a getter material, and subsequently exposed to ambient air, has been found to recover a pumping action after “in situ bakeout.
Abstract: Vacuum chambers sputter-coated with a thin film (∼1.5 μm) of a getter material, and subsequently exposed to ambient air, have been found to recover a pumping action after “in situ” bakeout. Coatings of Ti, Hf, Zr have been initially produced and studied, followed by their binary quasi-equiatomic alloys TiHf, HfZr, TiZr. All these coatings display activation at temperatures lower than 400°C, as observed by means of X-ray photoelectron spectroscopy, electron stimulated desorption (ESD), pumping speed and ultimate pressure measurements. The lowest activation onset temperature, about 200°C, has been measured for the quasi-equiatomic TiZr alloy. A further activation temperature decrease has been achieved for TiZr based ternary alloys/compounds, which are currently being investigated.
TL;DR: In this paper, the effect of the doping and annealing atmosphere on the electrical, optical and structural properties of the produced zinc oxide thin films has been investigated, and the most pronounced changes were observed in the films annealed in Argon.
Abstract: Undoped and doped (indium and aluminium) zinc oxide (ZnO) thin films have been prepared by spray pyrolysis, and the effect of the doping and annealing atmosphere on the electrical, optical and structural properties of the produced films has been investigated. The deposited films have a high resistivity. Annealing the films in an argon atmosphere or under vacuum leads to a substantial reduction of the electrical resistivity of the films and to an increase on the degree of cristallinity of the deposited material. The most pronounced changes were observed in the films annealed in Argon. The results also indicate that doping highly influences the electrical and structural properties of the films, which is more pronounced in the films doped with Indium.
TL;DR: In this paper, the reactive ion etching (RIE) of quartz and of silica-based glasses was examined in CF 4 /CHF 3 plasmas, and the etch rate was shown to reduce strongly with an increasing percentage of nonvolatile elements in the composition of the glass.
Abstract: The reactive ion etching (RIE) of quartz and of silica-based glasses (Suprasil 2, Herasil 2, BK7, LE, NA and soda-lime) has been examined in CF 4 /CHF 3 plasmas. The etch rate was shown to reduce strongly with an increasing percentage of non-volatile elements in the composition of the glass. The etching of the quartz and the Suprasil 2 and Herasil 2 glasses was consistent with a process of ion-enhanced chemical reaction as identified by Steinbruchel et al. J Electrochem Soc 1985; 132 (1): 180  . For these substrates, the etch rate was directly dependent on the square root of bias voltage in the RIE and increased with the ratio of CF 4 : CHF 3 in the gas mixture. The comparatively low etch rates of the LE (low expansion), soda-lime and NA (non-alkali) glasses were equivalent in both the CHF 3 /CF 4 and Ar plasmas, indicating a process of sputter etching. The BK7 glass has shown intermediate characteristics with a higher etch rate in CF 4 /CHF 3 than in an Ar plasma, indicating ion-enhanced chemical etching but with little dependence on the CF 4 : CHF 3 gas ratio. These results have been applied in the fabrication of grating patterns.
TL;DR: In this article, a range of carbon coatings from transparent, electrically insulating to black, conductive coatings, can be produced and the effects of the nature of the substrates with different hardness properties (M42, stainless steel and Al) are investigated.
Abstract: The Closed Field Un-Balanced Magnetron Sputter Ion Plating (CFUBMSIP) process is now routinely used in a production environment and is characterised by a high degree of flexibility in terms of the substrates and coating materials which can be used. Compared to classical magnetron sputtering the closed field system produces higher ion current density which gives high quality coatings and excellent adhesion. The ability to vary the deposition parameters over a wide range, permits the modification of not only the composition and the structure but also the morphology (density and growth mode) of the films. This paper describes, that in particular, a range of carbon coatings from transparent, electrically insulating to black, conductive coatings, can be produced. Tribological tests concerning adherence, hardness and wear properties in atmospheric and lubricated conditions are presented. The effects of the nature of the substrates with different hardness properties (M42, stainless steel and Al) are investigated.
TL;DR: In this paper, the preparation of layers of amorphous Ge x Se 1− x (with Ge atomic concentrations x = 0, 0.25 and 0.34) by plasma-enhanced chemical vapour deposition (PECVD) using the hydrides, GeH 4 and H 2 Se, as precursor gases was described in detail.
Abstract: The preparation of layers of amorphous Ge x Se 1− x (with Ge atomic concentrations x =0, 0.17, 0.25 and 0.34) by plasma-enhanced chemical vapour deposition (PECVD) using the hydrides, GeH 4 and H 2 Se, as precursor gases is described in detail. Information concerning the structure of the films was obtained from Raman spectroscopy. The optical transmission was measured over the 300 to 2500 nm spectral region in order to derive the refractive index and extinction coefficient of these PECVD films. The expressions proposed by Swanepoel, enabling the calculation of the optical constants of a thin film with non-uniform thickness, have successfully been applied. The refractive-index dispersion data were analysed using the Wemple–DiDomenico single-oscillator fit. The optical-absorption edges have been all of them described using the `non-direct transition' model proposed by Tauc. The optical gaps were calculated using Tauc's extrapolation, resulting in values ranging from 1.93 eV for a -Se to 2.26 eV for a -GeSe 2 .
TL;DR: In this article, polytetrafluorethylene (PTFE) was treated with N +, O + and C + ion beams with energies of 20 and 30 kV at 5 mA/cm 2 current density in the pulse regime.
Abstract: Polytetrafluorethylene (PTFE) was treated with N + , O + and C + ion beams with energies of 20 and 30 keV at 5 mA/cm 2 current density in the pulse regime. Structural changes were studied by IR ATR, XPS, IR diffuse reflectance spectra and wetting methods. After treatment the PTFE surface became chemically active to isocyanate, acrylamide and epoxy reagents, which caused a change of interface interaction with active adhesives. The durability of the PTFE adhesion joint to an epoxy adhesive increases by more than 100 times. The ion beam treatment can be used to increase adhesion joint durability of PTFE.
TL;DR: In this article, a fine grain near equiaxed microstructure was found to exhibit a compressive residual stress of 6.5 GPa in contrast to columnar Ti0.43Al0.53Cr0.03Y0.02N films.
Abstract: Ti0.43Al0.52Cr0.03Y0.02N films, which have been shown to exhibit a fine grain near equiaxed microstructure were found to exhibit a compressive residual stress of - 6.5 GPa in contrast to conventional columnar Ti0.44Al0.53Cr0.03N coatings which demonstrated - 3.8 GPa compressive stress. Novel coatings with this modified microstructure were also found to possess improved resistance to both dry oxidation and wet aqueous corrosion. Glancing angle parallel beam geometry X-ray diffraction (GAXRD) studies showed that in conventional Ti0.44Al0.53Cr0.03N films, severe oxidation initiated above 850 degrees C whilst oxidation of Ti0.43Al0.52Cr0.03Y0.02N started close to 950 degrees C. In an alkaline aqueous medium, Ti0.43Al0.52Cr0.03Y0.02N coatings deposited on steel showed an extended passive potential range and a significantly lower passive current compared with Ti0.44Al0.53Cr0.03N films of similar thickness. A similar improvement was evident in sulphuric acid where yttrium containing coatings passivated at high potential (Ti0.44Al0.53Cr0.03N films did not passivate). These effects may be ascribed to reduced porosity in the fine-grained Ti0.43Al0.52Cr0.03Y0.02N as well as the well-known effects of low concentrations of yttrium on high-temperature oxidation performance. (C) 1999 Elsevier Science Ltd. All rights reserved.
TL;DR: In this paper, the dry sliding wear of monolayer TiAlCrN and multilayer multi-layer TiAlN/CrN coatings was investigated against a BM2 tool steel counterface.
Abstract: The dry sliding wear of monolayer TiAlCrN and multilayer TiAlN/CrN coatings has been investigated against a BM2 tool steel counterface. The coatings were deposited on a BM2 tool steel substrate by combined steered-arc/unbalanced-magnetron deposition. Increasing either contact load or sliding speed led to a reduction in friction coefficient, typically from 1.1 to 0.2. Increasing load resulted in an increase in wear rate for both TiAlCrN and TiAlN/CrN (e.g. from 7 × 10-6 mm3/m at 22 N to 4 × 10-5 mm3/m at 189 N for the TiAlCrN monolayer coating, and from 7 × 10-6 mm3/m at 22 N to 2.5 × 10-5 mm3/m at 189 N for TiAlN/CrN multilayer). The wear rate for all coatings was at least an order of magnitude lower than the uncoated BM2 steel. The wear rate of the TiAlCrN coating tended to decrease with an increase in sliding speed (from 7.4 × 10-5 mm3/m at 0.2 m/s to 1.3 × 10-5 mm3 m at 1.1m/s) while the wear rate of the TiAlN/CrN was approximately constant as a function of sliding speed (approx. 1.5 × 10-5 mm3m).
TL;DR: In this article, optical parameters, n (λ ), k (λ ) and E 0, of TiO 2 thin films were obtained, using only optical transmittance measurements.
Abstract: Films prepared by reactive magnetron sputtering always present some structural and morphological heterogeneities. In this work, optical parameters, n ( λ ), k ( λ ) and E 0 , of TiO 2 thin films were obtained, using only optical transmittance measurements. Films were described according to Abeles's model. Using a mono-oscillator type dispersion curve for the refractive index and a Lorentzian type curve for the absorption coefficient, we were able to demonstrate that the films were optically equivalent to a porous layer, with some dispersion in film thickness. The detailed analysis of the experimental transmittance data, fitted between 330 nm to 2200 nm, also enabled us to correlate the effective refractive index of each film with its deposition conditions.
TL;DR: In this article, a new type of sputtering discharge and its applications for film deposition are described, which is a pulse, quasi-stationary and high-current diffuse discharge in the magnetic field.
Abstract: A new type of the sputtering discharge and its applications for film deposition are described in the paper. This is a pulse, quasi-stationary and high-current diffuse discharge in the magnetic field. The combination of its properties makes the discharge to be a promising instrument for film deposition. Complex films of high quality have been obtained by using this discharge. Features and areas of application are discussed.
TL;DR: In this paper, the basic mechanical and structural properties, as well as the oxidation behavior of Ti 1- x Al x N coatings sputtered at low temperature are reported. But the results were limited to the case of a sputtering at a temperature below 200°C.
Abstract: The basic mechanical and structural properties, as well as the oxidation behaviour of Ti 1- x Al x N coatings sputtered at low temperature are reported. Ti 1- x Al x N coatings of four different compositions were sputter deposited in a Sputron (Balzers) plasma-beam sputtering apparatus at a temperature below 200°C. Polished tool steel discs, silicon wafers and polished alumina ceramics were used as substrates. Oxidation of coatings was carried out by heating the samples at temperatures of 700–900°C in an oxygen atmosphere for selected times. The surface and fracture cross-sectional morphology of the as-deposited and oxidized films were studied by scanning electron microscopy, while the structure of the coatings was examined by the XRD and TEM techniques.
TL;DR: In this article, a micromachined mass filter made from silicon with Au metallised specially drawn glass fibres of length 30 mm and diameter 0.5 mm was mounted on a vacuum flange with a VG ANAVAC ion source and a Faraday plate collector.
Abstract: Conventional quadrupole mass filters are usually constructed from metallic rods of length 50—225 mm and diameters 5—15 mm. In this study the conventional arrangement has been replaced with a micromachined mass filter made from silicon with Au metallised specially drawn glass fibres of length 30 mm and diameter 0.5 mm. This assembly was mounted on a vacuum flange with a VG ANAVAC ion source and a Faraday plate collector. Conventional electronics were adapted to run at 6 MHz and mass spectra in the range 0—50 amu were obtained. The results indicate a linear mass scale with 5—10% valley separation between O 2 /N 2 peaks and a best resolution at 10% peak height of 2.7 amu at mass 40. It is believed that the recent improvements in performance are due to optimisation of the electronics coupled with refinements in the micromachining technique employed. ( 1999 Elsevier Science Ltd. All rights reserved.
TL;DR: In this article, the authors explored the gas flow measurement by means of orifices and Venturi tubes, which act as converters which transform a throughput to a difference pressure which can be conveniently measured.
Abstract: Numerous applications of vacuum technology require the measurement of gas throughput, as e.g. generation of calibration pressures, testing of vacuum pumps, thin film coating, and semiconductor manufacturing. Since primary methods for measuring gas flow are rather inconvenient, we have explored the gas flow measurement by means of orifices and Venturi tubes. These devices act as converters which transform a throughput to a difference pressure which can be conveniently measured. A thin orifice in the molecular flow regime and a Venturi tube in the viscous flow regime are almost fundamental converters whose characteristics can be calculated from first principles. Furthermore, these devices have high inherent stability. Thin orifices and Venturi tubes have been built and their characteristics for different gases were measured by fundamental methods. By varying diameter and inlet pressure, a wide flow range from 10 -7 to 10 5 mbar s -1 is covered. The experimental data are compared to calculated values and the characteristics are discussed.
TL;DR: In this paper, the properties of ZrCu and ZrN magnetron sputtered from an alloyed ZrNi (70/30/wt.%) target in Ar and Ar+N 2 at the same total pressure of 0.7
Abstract: The properties of ZrCu and ZrCu-N films magnetron sputtered from an alloyed ZrCu (70/30 wt.%) target in Ar and Ar+N 2 at the same total pressure of 0.7 Pa, respectively, are reported. Zr and Cu are immiscible elements in this composition range resulting in characteristic film properties. A ZrCu film sputter deposited on an unheated substrate was nanocrystalline and characterized by one very broad (about 8°) X-ray reflection line; the substrate temperature T s up to about 500°C did not affect the ZrCu nanocrystalline structure, but at T s >500°C a recrystallization process started with a polycrystalline ZrCu film being formed. Addition of nitrogen to the ZrCu film converted the nanocrystalline film to a nanocomposite; and to separate clearly individual phases of this nanocomposite its substrate needed heating. ZrCu-N films sputtered at T s ≥500°C were nanocomposites composed of Cu and ZrN. The microhardness of the ZrCu film was about 750 kg/mm 2 and that of the ZrCu-N film increased with increasing partial pressure of nitrogen but at≥0.3 Pa N 2 it reached a maximum at a value of 2200 kg/mm 2 . The microhardness of ZrCu-N films reactively sputtered at 0.3 Pa N 2 was almost constant up to T s =600°C.
TL;DR: In this article, the long-range effect of metal ion implantation was studied in alloys and in low ductility materials such as TiN. Microstructural studies of TiN coatings after MII were presented together with a model for the development of this effect.
Abstract: Ion implantation, with doses in the range 10 16 to 10 18 ion cm -2 , modifies the surface properties of many metallic and ceramic materials. Whilst gas ion beams are currently employed extensively, metal ion implantation (MII) systems have been developed based on the vacuum metal arc and a brief review of these systems is presented. Examples of industrial applications are given using, primarily, Mo ions which harden the surface of steel, increase its corrosion resistance and lower the coefficient of friction of the alloyed (or implanted) zone, IZ. Extending well beyond this zone, a dislocation network is developed which hardens the material in depth. Termed the long-range effect , this occurs in alloys and in low ductility materials such as TiN. Microstructural studies of TiN coatings after MII are presented together with a model for the development of this effect. The results show that the stress field in TiN made by PVD is modified by implantation but no effect on the grain structure is found, whereas in TiN made by CVD the residual stress is not changed but growth of fine grains within the original grain structure is observed.
TL;DR: In this paper, two (Cr,Ta)N coatings with different composition were deposited in a Sputron plasma beam sputtering apparatus at a temperature below 200°C on polished tool steel disks, polished alumina substrates and silicon wafers.
Abstract: Two (Cr,Ta)N coatings with different composition were deposited in a Sputron plasma beam sputtering apparatus at a temperature below 200°C on polished tool steel disks, polished alumina substrates and silicon wafers. Microhardness, adhesion and internal stress were measured by Vickers microindentation, the scratch test and sample deflection, respectively. The mechanical and electrical properties were compared to the values of CrN and TaN binary nitride coatings prepared in the same device under similar conditions. Like CrN and TaN, (Cr,Ta)N crystallizes in a cubic (NaCl) structure. Oxidation resistance was tested in the temperature range 550–850°C. We observed that a chromium-rich protective oxide layer developed on the Cr 0.58 Ta 0.42 N coating, while on the Cr 0.17 Ta 0.83 N coating the oxidation was more rapid, with cracks appearing at temperatures as low as 600°C.
TL;DR: In this article, the hydrogen pressure inside a well-baked stainless steel container was found to saturate at about 0.2mPa under seal-off conditions at room temperature.
Abstract: Carbon monoxide and other carbon derivatives were considered for a long time as intrinsic constituents of the residual atmosphere inside a UHV (ultra high vacuum) apparatus. It is gradually being accepted now that the residual gas in stainless steel containers is virtually pure hydrogen. Impurity gases, especially carbon monoxide, are generated at a significant rate by ion gauges and mass spectrometers due to ion-induced surface processes. Impurity gases may severely affect sensitive surface analysis and processes. It is proposed that a definition of XHV (extremely high vacuum) conditions should include the requirement that ion-induced impurity gases are excluded. It is demonstrated that much longer baking times than practiced today are required for rigorous outgassing of stainless steel. The hydrogen pressure inside a well baked stainless steel container was found to saturate at about 0.2 mPa under seal-off conditions at room temperature.
TL;DR: In this paper, a characterization of amorphous plasma enhanced chemical vapour deposited (PECVD) silicon oxide films suitable for integrated optics applications is reported. But the composition of the layers depends mainly on the reactant gas flow ratio.
Abstract: Deposition and characterisation of amorphous plasma enhanced chemical vapour deposited (PECVD) silicon oxide films suitable for integrated optics applications is reported. Film properties such as refractive index, density, growth rate, thickness, bonded hydrogen content and total stress are correlated to deposition parameters such as gas flow ratio and substrate temperature. The composition of the layers depends mainly on the reactant gas flow ratio. For flow ratios greater than about 20, film properties were found to match the corresponding properties of silicon thermal oxide.
TL;DR: In this paper, the performance of novel CrN/NbN superlattice coatings in comparison with a commercial CrN coating and a 304L control specimen was evaluated.
Abstract: Potentiodynamic polarisation experiments have been used to evaluate the corrosion performance of novel CrN/NbN superlattice coatings in comparison with a commercial CrN coating and a 304L control specimen. In addition, electrochemical impedance has been used to determine the effective surface area of the coatings by capacitance measurements. Results indicate that the superlattice coatings have significantly improved barrier properties evidenced by increases in pitting potentials of up to 500 mV compared with 304L. Furthermore, the impedance evidence indicates that CrN has comparatively large pores while the superlattice coatings have extensive, but diffuse and fine-scale, surface porosity confirming that the corrosion performance improvement is most likely due to microstructural enhancements. (C) 1999 Elsevier Science Ltd. All rights reserved.
TL;DR: In this paper, a comparative study of modifications produced by Nitrogen implantations on three different commercial alloys is presented, where different Nitrogen doses have been implanted, hardness and wear tests have been carried out to investigate the influence of implantation parameters.
Abstract: Ion implantation of Aluminum is a useful technique to improve hardness and tribological properties. This paper reports on a comparative study of modifications produced by Nitrogen implantations on three different Al commercial alloys. Different Nitrogen doses have been implanted, hardness and wear tests have been carried out to investigate the influence of implantation parameters. Tribological changes are referred to implantation dose and to thermal post-treatments, as well as to testing conditions. Applications are relevant in aeronautical and moulding sectors.
TL;DR: In this paper, the authors studied the reaction kinetics in dependence on the afterglow time in accordance with experimental data and found that the energy of excited particles is reduced, and the limited amount of reactions is important.
Abstract: Chemical reactions initiated by the dissociation of methane in the nitrogen flowing afterglow have been studied by the computer modelling. The input experimental data were obtained from the microwave CH4/N2 plasma. The modelling of methane decomposition was based on a macroscopic kinetic approach. The 24 neutral and excited species were introduced: electrons, hydrocarbons, radicals, neutral and excited gases, and nitrogen containing species. Between these species 61 chemical reactions were studied. It was found that in the flowing afterglow conditions, where the energy of excited particles is reduced, the limited amount of reactions is really important. With the aid of this simplified model of 18 chemical reactions the yield of stable products and the detailed kinetics of their creation in the dependence on activity of individual species were studied. Special attention was devoted to the study of reaction kinetics in dependence on the afterglow time in accordance with experimental data.
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to study the nanoscale morphologies of the coatings.
Abstract: Sol-gel derived SiO2, TiO2, xSiO2−(100−x)TiO2 (where x=10, 20, 40, 50, 60, 80 mol%) films on silicon substrates were nitrided by ammonia treatment at 1200°C. The structural transformations occur in silica–titania films as a result of ammonolysis. These transformations were studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS spectra of nitrided films showed that Ti atoms are bonding to nitrogen as well as to oxygen. The shape of the Ti(2p) spectra are changed after nitridation and after deconvolution of at least three components, related to oxide, oxynitride and nitride can be detected. AFM was used to study the nanoscale morphologies of the coatings. AFM observations revealed that all nitrided films containing more than 40 mol% TiO2 are almost completely covered by TiN nano-crystals that increase in size with TiO2 content. Oxide and oxynitride phases are responsible for the bonding between the TiN nano-crystals and the silicon substrate.
TL;DR: In this article, the authors investigated the time dependence of water adsorption on polycrystalline barium titanate films fabricated on silicon under hydrothermal conditions and found that the typical amplitude change was about 0.05 eV for a 50% humidity variation, with higher variations at lower humidity.
Abstract: We have investigated the time dependence of water adsorption on polycrystalline barium titanate films fabricated on silicon under hydrothermal conditions. X-ray photoelectron spectroscopy showed surface OH groups on the films but no molecular H 2 O. The time dependent behavior of water adsorption was investigated by measuring the work function changes with a Kelvin probe. The film response time for both increasing and decreasing humidity is less than one minute. The typical amplitude change was about 0.05 eV for a 50% humidity variation, with higher variations at lower humidity.
TL;DR: The results of the volume ratios obtained with the spinning rotor gauge method were in agreement (relative differences ≤ 3×10 -4 ) with the results obtained with either of the two other independent methods.
Abstract: Static or volume expansion systems are used to generate accurately known pressures in the high and medium vacuum range for vacuum gauge calibrations. To determine the volume ratios in such systems, different methods can be used. We have tested the method of using a spinning rotor gauge for measuring pressures before and after an expansion for several gases and compared it with two other independent methods. The results of the volume ratios obtained with the spinning rotor gauge method were in agreement (relative differences ≤3×10 -4 ) with the results obtained with either of the two other methods.
TL;DR: In this paper, the influence of the acetylene flow rate on the tribological properties of TiC films produced by cathodic arc plasma deposition (CAPD) on the high-speed steel substrates was investigated.
Abstract: The influence of the acetylene flow rate on the tribological properties of TiC films produced by cathodic arc plasma deposition (CAPD) on the high-speed steel substrates was investigated. The following properties of films were tested: phase and chemical composition, microhardness, adhesion characterised by the scratch method, thickness, fracture morphology (by SEM), surface roughness, friction coefficient and abrasive wear (by ball-on-disk method). The flow rate of acetylene was changed between 20–250 sccm by constant substrate bias voltage of −70 V. The highest values of microhardness of coatings were obtained at a flow rate between 70 and 140 sccm. The maximum of 43 GPa value was achieved at a flow rate of 70 sccm. At flow rates of 20 and above 180 sccm, the microhardness was about 16 GPa. The friction coefficient reaches the value of 0.2, its decreasing is caused by the increase in flow rate of acetylene. Coating abrasive wear also decreases. The highest values of abrasive wear were obtained at the acetylene flow of 20 sccm, for which the dry friction coefficient was 0.54. The abrasive wear of the counter-specimen (ball) gets also bigger for higher values of the dry friction coefficient. By X-ray examination of crystalline structure, reflexes from (1 1 1)TiC and (2 2 0)TiC planes were recorded; they disappear at higher acetylene flow rates. This may be the result of an amorphisation process of the film structure.
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) and scanning Auger microscopy (SAM) have been used to study two ancient objects of the Vatican Museums: a Roman bronze found in seawater, and an Etruscan bronze, found in soil.
Abstract: X-ray photoelectron spectroscopy (XPS) and scanning Auger microscopy (SAM) have been used to study two ancient objects of the Vatican Museums: a Roman bronze, found in seawater, and an Etruscan bronze, found in soil. The main purpose of this work is to evaluate the degree to which XPS and SAM are capable of revealing the effects of different burial sites on the surface microchemistry of these bronzes. We find that seawater causes the build-up of copper sulfides and lead carbonates/oxides on the bare surface of the Roman object, whereas the original patina is rich in copper chlorides, although sulfides are still detected. Moreover, fair evidence is given that during its use this bronze had been subjected to deliberate smearing with oil or pitch for conservation purposes. By way of contrast, soil made the surface of the Etruscan bronze rich in a mixture of copper chlorides and oxides. Tin, entirely present as an SnO2-like phase, is more abundant, as is metallic copper, in the Etruscan bronze than in the Roman one. These results compare favorably with findings of other authors on `modern’ Cu3Sn. In this same object, SAM highlights lateral chemical heterogeneities with a spatial resolution ∼2,000 A. Our results are related to other studies conducted on bronze objects analyzed with bulk-sensitive methods, as well as to the reports of historical sources.
TL;DR: In this paper, the optical gap energy of glassy Te46-xAs32+xGe10Si12 alloys was calculated for the amorphous Te46xAs 32+x Ge10Si 12 system under vacuum with x = 0, 1, 2, 4 and 5.
Abstract: The structure has been examined theoretically of the glassy Te46-xAs32+xGe10Si12 substances that have semiconducting properties of potential use as memory switching elements in a variety of electronic devices. The optical gap Eg has been calculated for the amorphous Te46-xAs32+xGe10Si12 system prepared under vacuum with x=0, 1, 2, 4 and 5 . These calculation were based mainly on the volume fraction and the optical gap of each element of the alloys. The glass transition temperature Tg was compared with an arbitrarily defined optical gap energy E04 and Tg provided an index of atomic mobility and E04 an index of the covalent bond strength. The nearest neighbour coordination number was also defined for the system under study. The relationship between E04 and chemical composition in the vacuum prepared Te46-xAs32+xGe10Si12 is discussed in terms of the average heat of atomization Hs and average cordination number m. The later are computed from the heats of atomization and the coordination number of used elements, respectively. From the calculation the Tg–E04 correlation is interpreted in terms of a proposed fluidity equation for covalent liquids with 2.76≤m≤2.81.
TL;DR: In this article, the effect of antimony in concentrations from 0.01 to 0.20% to Se0.75Ge0.25-y glass on its dc conductivity is analyzed.
Abstract: The effect of the addition of varying amounts of antimony in concentrations from 0.01 to 0.20 at% to Se0.75Ge0.25-y glass on its dc conductivity is analysed. The electrical conductivity of amorphous thin films of vacuum evaporated Se0.75Ge0.25-ySby were determined during and after light exposure and at different temperatures. The time dependence of the electrical conductivity measured in darkness or when exposed to light at about room temperature has been studied for amorphous Se0.75Ge0.25-ySby (y=0.01, 0.05, 0.10, 0.15, 0.18 and 0.20) thin films of different compositions and different thicknesses. The conduction activation energy ΔE and the pre-exponential factor σ 0 (0, T) which appear in the dc conductivities are found to decrease with increasing Sb content. The mean value of the threshold voltage, was measured either in darkness, V th , and after exposure of light V th il , for different compositions and temperatures. The pronounced glass-forming tendencies of alloys of Se and Ge with Sb were discussed topologically in terms of the chemical bonds expected to be present in these materials. These chemical bonds have been used to estimate the cohesive energies (CE) of the glasses.
TL;DR: In this article, a planar magnetron sputtering system with an additional plasma confinement which can be operated at low argon pressures (down to 3.4×10−2
Abstract: Langmuir probe measurements have been carried out in a planar magnetron sputtering system with an additional plasma confinement which can be operated at low argon pressures (down to 3.4×10−2 Pa) when target utilization greater than 80% can be achieved. The electron density, electron temperature, relative densities of low- and high-energy groups of electrons and the difference between the plasma and floating potential have been determined in various positions between the target and a substrate at the argon pressures in the range from 0.05 to 5 Pa. It has been proved that the additional magnetic field results, particularly in larger distances from the target at lower pressures, in the formation of structured electron energy distributions with a substantial contribution from a high-energy group of electrons, which is responsible for enhanced gas ionization and relatively high values observed for the difference between the plasma and the floating potential.