Hard decorative TiN coatings by ion plating

Gold-coloured hard coatings of TiN have been obtained on carbon steel, stainless steel and stellite substrates by ion plating titanium in an atmosphere of nitrogen. Pure, stoichiometric and compact layers display a gold colour. The titanium evaporation source was heated by a 90°-deflected electron beam obtained from a cold-cathode discharge gun. Typically, deposition rates up to 500 Å min^?1 have been obtained. Particular attention was paid to the problem of adherence of the deposited layers to the substrate. Thin (approximately 0.2 μm) coatings deposited onto pulished substrates reproduce the original brilliance. Thicker coatings are dull and need some additional mechanical polishing. The colour of the coatings was identified by reflectance spectra and chromaticity coordinates. Abrasion tests performed on coated pieces showed excellent resistance to abraison.     

The properties of Al doped ZnO thin films deposited on various substrate materials by RF magnetron sputtering

Transparent conductive Al-doped ZnO (AZO) thin films were deposited on various substrates including glass, polyimide film (PI) and stainless steel, using radio frequency magnetron sputtering method. The structural, electrical and optical properties of AZO thin films grown on various substrates were systematically investigated. We observe that substrate materials play important roles in film crystallization and resistivity but little on optical transmittance. X-ray diffractometer study shows that all obtained AZO thin films have wurtzite phase with highly c-axis preferred orientation, and films on glass present the strongest (002) diffraction peaks. The presence of compression stress plays critical role in determining the crystalline structure of AZO films, which tends to stretch the lattice constant c and enlarge the (002) diffraction angle. Although the films on the glass present the finest electrical properties and the resistivity reaches 12.52 × 10-4 Ωm, AFM study manifests that films on flexible substrates, especially stainless steel, bestrew similar inverted pyramid structure which are suitable for window material and electrode of solar cells. The average optical transmittance of AZO thin films deposited on glass and PI are both around 85% in the visible light range (400–800 nm).     

Amorphous and amorphous-crystalline coatings of stainless steel with addition of refractory metals obtained by magnetron sputtering in vacuum

Amorphous and amorphous-crystalline stainless steel films were obtained with additions of Ti or W. The deposition rate was v = 6–630 nmmin⁻¹, the thickness h = 50 to 5000 nm and the substrate temperature T_s varied from 77 to 293 K. A magnetron compound target was used for sputtering and coatings were deposited on Al, steel, glass-ceramic and Corning glass substrates. Structural data for the coexistence of amorphous and amorphous-crystalline phases in stainless steel films are presented. A study was made of the structure sensitive properties: specific electrical resistivity and magnetic characteristics. Some data were obtained for films Fe + Ti and Fe + W, prepared by the same method. Properties affecting the practical application of such amorphous and amorphous-crystalline metal coatings were also studied.     

Resistivity and photoconductivity of plasma-sprayed polycrystalline silicon

Polycrystalline silicon layers of area 8 cm² and thickness t ranging from 100 μm to 2 mm were prepared on alumina substrates by plasma spraying silicon powder. For t > 500 μm, these layers could be detached from the substrate. The conductivity could be made n or p type by in situ doping. The microstructure, impurity content and resistivity as a function of both phosphorus and boron doping concentrations were studied. The effect of heat treatment on the resistivity, Hall mobility and the photoconductivity is reported. The data are explained qualitatively on the basis of existing models of the transport behaviour of polycrystalline silicon.     

A.C. properties of discontinuous metal thin films

Conductivity and Hall effect investigations have been carried out on ion beam sputtered silicon layers on spinel substrates, in a temperature range from 80 K to 600 K. For silicon layers of thickness 8 μm, the observed mobilities at room temperature were in agreement with the values for the bulk material. In silicon films of thickness 1 μm, lower values for μ were found. The difference can be interpreted by considering additional scattering at crystal defects. By making simple assumptions about the influence of these defects, a satisfactory explanation for the dependence of mobility on temperature can be given.     

Precision crystal corner cube arrays for optical gratings formed by (100) silicon planes with selective epitaxial growth

High-quality, micrometer scale, corner cube arrays were grown on (111) silicon substrates by selective epitaxial growth (SEG) techniques. Sixteen different arrays were produced that had periodic corner spacing ranging from 3 to 50 μm. The arrays were formed by suppressing silicon SEG in a regular geometric pattern, producing the three mutually perpendicular (100) smooth crystal planes. For coherent light of 633-nm wavelengtha sharp diffraction pattern of threefold symmetry was observed out to 7 maxima, as well as a retroreflection component.     

Microcontact Printing: Arrays of Silicon Micro/Nanostructures Formed in Suspended Configurations for Deterministic Assembly Using Flat and Roller‐Type Stamps (Small 4/2011)

The ability to create and manipulate large arrays of inorganic semiconductor micro/nanostructures for integration on unconventional substrates provides new possibilities in device engineering. Here, simple methods are described for the preparation of structures of single crystalline silicon in suspended and tethered configurations that facilitate their deterministic assembly using transfer‐printing techniques. Diverse shapes (e.g., straight or curved edges), thicknesses (between 55 nm and 3 μm), and sizes (areas of 4000 μm² to 117 mm²) of structures in varied layouts (regular or irregular arrays, with dense or sparse coverages) can be achieved, using either flat or cylindrical roller‐type stamps. To demonstrate the technique, printing with 100% yield onto curved, rigid supports of glass and ceramics and onto thin sheets of plastic is shown. The fabrication of a printed array of silicon p⁺–i–n⁺ junction photodiodes on plastic is representative of device‐printing capabilities.     

Elastic properties measurement of glass layers fabricated onsilicon wafers for microelectronics and micromachines

Elastic properties such as the Young's modulus, the Poisson's ratio and the density of Si-B-O glass layers fabricated on (100) silicon substrates by the flame hydrolysis deposition method were measured. Thicknesses of the layers were about 20 μm. It was found that the Young's modulus decreased with the boron dopant concentration. The Poisson's ratio was about 0.26 regardless of the boron dopant concentration. The measured elastic properties will be used in the design of micromachines fabricated with silicon substrates and glass layers     

Low-pressure growth of single-crystal silicon carbide

We report on a low-pressure, reproducible process for producing large-area device-quality single-crystal silicon carbide (SiC) on 〈100〉 and 〈111〉 p-type silicon substrates. The process has been used to produce epitaxial layers up to 20 μm thick, and 2″ in diameter. The unintentional doping (n-type) was in the 10¹⁷ cm⁻³ range with mobilities of several hundred cm²/V s.     

X-ray photoemission studies of cesium antimonide photoemitters

X-ray photoemission spectra (XPS) of cesium antimonide photosurfaces prepared in ultrahigh vacuum on Pyrex, Suprasil quartz and stainless steel substrates were measured. A comparison of the XPS data for xenon gas, which is isoelectronic with Cs⁺, and cesium in good cesium antimonide photoemitters indicates that cesium exists predominantly in the form Cs⁺, in direct conflict with present theories concerning this surface. Measurements also indicated a slight excess of antimony above that given by the formula Cs₃Sb. Band bending is only inferred from the shifts of the cesium core levels as a function of photosensitivity.     

Impact of small steel spheres on glass surfaces

A high speed photographic study has been made as part of a detailed investigation of the impact of small steel spheres ( 800 and 1000 m diameter) on to Pyrex and soda-lime glasses. The velocity of the spheres was varied from 20 to 300 m sec^–1 and the fracturing process during the complete impact cycle was followed. Observations revealed substantial differences in the behaviour of the two glasses, particularly at higher velocities; Pyrex behaved as though indented by a sphere, whereas soda lime glass behaved as though indented with a pointed indenter. As with quasi-static pointed indentations, cracking was observed during the unloading cycle. It was also found that the angle of the Hertzian cone crack in Pyrex glass varied in a systematic manner with velocity. Rebound velocity, time of contact and extent of flattening of the steel spheres were also recorded. The relevance of these observations to impact erosion and strength degradation of brittle materials is pointed out.     

Structure and properties of ion-nitrided stainless steels

The structure and properties of ion-nitrided layers on several stainless steels, 410 martensitic stainless steel, 430 ferritic stainless steel and 321 austenitic stainless steel, has been studied under varying process conditions with microhardness-depth correlations, optical microscopy and transmission electron microscopy. The process variables studied include time (2 to 10 h) and temperature (400 to 600° C). The highest case depth values and hardness levels were observed in martensitic stainless steels. The lowest case depths were observed in austenitic stainless steel. In general, the behaviour of matensitic and ferritic stainless steels were similar. All three steels showed increasing case depths and decreasing surface hardnesses with increasing ion-nitriding temperatures and times. Nitriding depth was found to be parabolic with ion nitriding time in all three steels at all ion-nitriding temperatures investigated, the nitriding reaction being faster in martensitic stainless steel than the others. Electron microscopy showed that almost no structural difference arises in the core of ferritic and austenitic stainless steels whereas recrystallization of the martensitic structure was observed in the core of martensitic steel following ion nitriding. Electron microscopy results also showed that ion nitriding produces platelets or disc-shaped precipitates on {001} matrix planes, coherent with the matrix. These platelets showed a striated morphology which is thought to be the result of the elastic strain in the matrix.     

Structural and optical characterization of CdS and CdHgTe thin films for the fabrication of CdHgTe/CdS structure

This article presents the deposition and characterization of CdS and CdHgTe thin films for the fabrication of CdHgTe/CdS structure. The growth of CdS and CdHgTe thin films on FTO-coated conducting glass substrates have been performed by chemical bath deposition (CBD) and electrodeposition methods, respectively. The deposition conditions have been optimized for getting better quality layers of CdS and CdHgTe. The grown layers of both CdS and CdHgTe have been characterized by photoelectrochemical cell (PEC) measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis spectrophotometer. Annealing effect of the deposited films has also been investigated. Finally the fabrication of CdHgTe/CdS structure has been performed and investigated by I–V characteristics. PEC, XRD, SEM and UV–vis spectrophotometer studies reveal that chemically deposited CdS layers are n-type with band gap values vary from 2.29 to 2.41 eV and cubic with (111) preferential orientation, and have spherical grain distributed over the surface. However, electrodeposited CdHgTe layers are p-type with band gap values varying from 1.50 to 1.53 eV and cubic with highly oriented CdHgTe crystallites with the (111) planes parallel to the substrate, and have uniform distribution of granular grains over the surface. The fabricated CdHgTe/CdS structure gave an open-circuit photovoltage and a short-circuit photocurrent of 510 mV and 13 mA/cm² respectively, under AM 1.5 illumination.     

Spectral and current-voltage characteristics of Si-Si<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>x</Subscript> heterostructures grown by liquid phase epitaxy

The spectral and current-voltage (I–V) characteristics of Si-Si_1?xGe_x heterostructures grown by liquid phase epitaxy on silicon substrates were studied. The dependence of the longwave photosensitivity boundary of these structures on the variband solid solution composition was determined. It is shown that these variband solid solutions can serve as transition buffer layers between silicon substrates and a structure based on a different semiconductor. These structures can be employed in elements converting a part of the IR solar radiation in cascade solar cells and in photodetectors for the optical fiber communication lines transmitting signals with the wavelengths λ=1.33 and 1.5 μm.     

The deposition of hard surface layers by hydrocarbon cracking in a glow discharge

Hard surface layers with a Vickers hardness of greater than 2000 have been deposited on titanium alloys, Nimonic, high tensile steel and stainless steels by cracking ethylene in a glow discharge. Thin deposits were extremely tenacious, but films thicker than 3–5 μm tended to blister and peel away from the substrate.     

ZnS molecular beam epitaxy on silicon substrates

We report on the deposition of ZnS films of high structural quality onto Si(100) substrates. Films with thicknesses from 0.75 to 4 μm were examined by X-ray diffraction in both the Bragg and Read configurations. The ZnS 400 peak in Cu Kα₁ X-ray diffraction had a linewidth of 0.04°–0.06°, comparable with that of the silicon substrate. The high structural quality of these films suggests their use as buffer layers for II-VI device growth.     

Étude de la cinétique de croissance de couches ZnSe ET ZnS épitaxiées sur fluorine par transport en phase vapeur

Epitaxial layers of ZnSe and ZnS were grown on (111) calcium fluoride (CaF₂) substrates in an open tube system by reaction of hydrogen with the compounds in powdered form. Typical growth rates of 1–2 μm h^?1 for ZnSe and 3–5 μm h^?1 for ZnS have been obtained. The parameters investigated were source temperature, substrate temperature and hydrogen flow rate.The experimental results were compared with theoretical growth rates calculated from the partial pressures of the components. In this case, the growth rate is proportional to the concentration difference between the source and the substrate and contains one adjustable parameter which depends on the substrate temperature and vapour phase composition.     

X-ray determination of strain and texture in sputtered molybdenum and titanium films on silicon

Molybdenum and titanium films prepared with a rotating r.f. diode system were examined by X-ray diffraction for strain and texture. Both films were deposited onto (111)-oriented silicon crystal substrates. Molybdenum films 1.13 μm thick sputtered with a target voltage of -2.7 kV, a zero substrate bias and an average temperature of 180°C were in compression on cooling to room temperature. Pole density plots for the (200), (211), (220), (222), (301) and (321) planes gave relatively sharp peaks. The (220) plane showed a strong peak parallel to the (111) plane on silicon. In contrast, a 1.25 μm titanium film was found to be in tension after sputtering at -2.7 kV, a substrate bias of -50 V and an average temperature of 180°C. Relatively broad pole density plots were found for the (002) and (110) planes. The (100) and (110) planes gave peaks parallel to (111) Si. Intrinsic strains from embedded argon were determined from χ scan X-ray data.     

High speed scanning electron beam annealing of ion-implanted silicon layers

Sawtooth scanning with a 40 keV electron probe at frequencies of 10⁵–10⁶ Hz can be used for generating in a silicon surface a quasi-line-shaped temperature field. With a power of 70–80 W and a spot diameter of 50 μm this yields a surface temperature of about 1500 K. The procedure was tentatively used for solid state annealing of ⁷⁵As-ion-implanted silicon layers to a depth of 1000 Å. These beam parameters permit an areal throughput of 10 cm² s^-1 without back side cooling since the substrate temperatures at the back side can be kept below 800 K.     

Electrical and mechanical properties of electrically conductive polyethersulfone composites

Electrically conductive polyethersulphone (pes) composites containing carbon fibres, nickel fibres, stainless steel fibres or aluminium flakes at various volume fractions up to 40% were fabricated and tested. For electromagnetic interference (emi) shielding effectiveness > 50 dB, the minimum filler volume fraction was 40% for carbon fibres of length 200 or 400 μm, 20% for nickel or stainless steel fibres, and 30% for aluminium flakes. The tensile strength first increased and then decreased with increasing filler content, such that the highest tensile strength occurred at 30 volume% (vol%) for carbon fibres (of length 200 or 400 μm) as the filler and at 10 vol% for nickel or stainless steel fibres. However, for carbon fibres (of length 100 μm) and aluminium flakes, the tensile strength increases up to at least 40 vol%. The best overall performance was provided by aluminium flakes at 40 vol%; the resistivity was 7 × 10⁻⁵ Ω cm, the emi shielding effectiveness was > 50 dB and tensile strength was 67 MPa. The resistivity of the aluminium flake composites was not affected by heating in air at 140°C for up to at least 144 h.