Effect of the nanostructuring of a Cu substrate on the fracture of heat-resistant Si-Al-N coatings during uniaxial tension

The effect of the nanostructuring of the surface layers in a Cu substrate on the microstructure, mechanical properties, and fracture mechanisms of heat-resistant Si-Al-N coatings during uniaxial tension is studied. The nanostructuring of a substrate is performed by the following two methods: bombardment by Zr⁺ ion beams and ultrasonic impact treatment. Depending on the state of the substrate, different spallation mechanisms are found to operate in the Si-Al-N coatings during mechanical loading. The maximum shear strength of the coating/substrate interface is shown to be achieved due to ion bombardment of the substrate.     

Structural modification of TiAlN coatings by preliminary Ti Ion bombardment of a steel substrate

The TiAlN coatings deposited onto steel 12Cr18Ni9Ti substrates before and after preliminary treatment by Ti ion beams are studied by X-ray diffraction, transmission electron microscopy, atomic force microscopy, and nanoindentation. The modification of the surface layer of a substrate is shown to change the structure and the preferred orientation of the coatings. The mechanical properties of the TiAlN coatings are found to depend substantially on the ion bombardment time.     

Control of the structure and stress state of thin films and coatings in the process of their preparation by ion-plasma methods

A system analysis of the influence of the substrate temperature during deposition on two main factors (nanodimensionality of structural aggregates and high stresses) responsible for the nonequilibrium state of the materials of ion-plasma-deposited films and coatings has been performed. It has been shown that an increase in the temperature during deposition leads to a preferred growth of nanocrystallites in the direction of incidence of film-forming particles, which, in turn, results in the formation of an anisometric crystal structure. The main causes of the generation of high elastic stresses in ion-plasma condensates are the ion/atom bombardment in the process of deposition (which stimulates the development of compressive stresses) and the difference in the thermal expansion coefficients of the condensate and substrate materials (which initiates the development of thermal stresses; the sign is determined by the difference between the thermal expansion coefficients of the condensate and substrate materials). An increase in the temperature during deposition results in the relaxation of compressive stresses stimulated by the ion/atom bombardment and in an enhancement of the influence of thermal stresses on the state of the ion-plasma condensate. This makes it possible to control the stress state of ion-plasma films and coatings by purposefully varying the substrate temperature during deposition.     

Study on formation and shape of carbon nanotips depending on ion bombardment

Carbon nanotips were grown from carbon film deposited on silicon substrate by plasma-enhanced hot filament chemical vapor deposition. The carbon film and carbon nanotips were investigated by scanning electron microscopy and micro-Raman spectrometry, respectively. The results indicate that the carbon film is composed of amorphous carbon and the carbon nanotips are characteristic of nanographite, and their formation and shapes depend on ion bombardment strongly. Simultaneously, the number of forming the carbon nanotips is increased by the ion bombardment. Because there are ion deposition and sputtering-etching in the process of growing of the carbon nanotips, the theory related to ion deposition and sputtering was used to obtain their formation condition and analyze effects of the ion bombardment on their shapes and the number of forming them.     

Use of ion processing to improve the quality of fullerene-coated field emitters

The efficiency of tip field emitters covered by activated fullerene coatings is studied in a wide range of emission currents and residual gas pressures. Main mechanisms behind the influence of the gaseous medium and ion bombardment on the emitter efficiency are determined. The feasibility of improving the homogeneity of the fullerene coating by potassium ion bombardment is demonstrated. From data on the emitter performance in a technical vacuum, a previously unknown effect is discovered: the structure of activated fullerene coatings is reproduced under intense ion bombardment. It is found that intense bombardment by residual gas ions increases a limiting current extracted from fullerene-coated tip field emitters.     

离子的轰击对Si衬底上金刚石核附着力的影响

利用扫描电子显微镜和原子力显微镜对负衬底偏压增强金刚石核化的过程进行了分析,从理论上探索了负衬底偏压作用下离子的轰击效应增强金刚石核在Si衬底上附着力的机理,给出了金刚石核与衬底的附着力和衬底负偏压之间的关系.     

离子的轰击对Si衬底上金刚石核附着力的影响

利用扫描电子显微镜和原子力显微镜对负衬底偏压增强金刚石核化的过程进行了分析,从理论上探索了负衬底偏压作用下离子的轰击效应增强金刚石核在Si衬底上附着力的机理,给出了金刚石核与衬底的附着力和衬底负偏压之间的关系.     

Composition and corrosion resistance of coatings on the basis of nitrides of titanium and chromium

Ti-Cr-N coatings were deposited on a low-carbon steel St3 substrate by overlapping of Ti and Cr plasma flows in residual nitrogen atmosphere using ion bombardment. Auger electron spectroscopy and X-ray diffraction were used to analyze the element and phase composition of the deposited coatings. It was established that, under constant deposition conditions (the arc current, gas pressure, bias voltage), coatings possess the fcc structure of a (Ti,Cr)N solid solution with uniform distribution of elements along the depth. The growth of the substrate bias voltage leads to an increase of titanium concentration in the coating due to changes in the interaction processes (condensation and sputtering) of the deposited materials with the substrate. Corrosion tests of the coatings and steel St3 were performed in acid (1 M H₂SO₄) and salt (3% NaCl) media. It was found that the corrosion processes progress less intensely in salt solution than in acid medium.     

Mechanical properties of Mo-Ru thin films with Ni interlayer of different thickness

Noble metal coatings are usually introduced to increase lifetime of glass molding die. In this study, Mo-Ru coatings with Ni interlayer were deposited on tungsten carbide by DC sputtering processes at an elevated temperature of 550 °C to modify the properties in molding die materials. Phase identification was investigated by X-ray diffractometry (XRD). The surface morphology and composition of coatings were evaluated by atomic force microscopy (AFM) and field-emission electron probe microanalyzer (FE-EPMA), respectively. Hardness of the Mo-Ru films was measured by nanoindentation testing. In the aspects of adhesion, the influence on interlayer of different thickness was probed by the scratch test, and the different composition of Mo-Ru resulted in various kinds of fracture configurations. The scratch test exhibited spalling and chipping failure between substrate and layer.     

Influence of Si substrate preparation on surface chemistry and morphology of L-CVD SnO2 thin films studied by XPS and AFM

Results of experimental studies of the influence of substrate preparation on the surface chemistry and surface morphology of the laser-assisted chemical vapour deposition (L-CVD) SnO₂ thin films are presented in this paper. The native Si(1 0 0) substrate cleaned by UHV thermal annealing (TA) as well as thermally oxidized Si(1 0 0) substrate cleaned by ion bombardment (IBA) have been used as the substrates. X-ray photoemission spectroscopy (XPS) has been used for the control of surface chemistry of the substrates as well as of deposited films. Atomic force microscopy (AFM) has been used to control the surface morphology of the L-CVD SnO₂ thin films deposited on differently prepared substrates. Our XPS shows that the L-CVD SnO₂ thin films deposited on thermally oxidized Si(1 0 0) substrate after cleaning with ion bombardment exhibit the same stoichiometry, i.e. ratio [O]/[Sn] = 1.30 as that of the layers deposited on Si(1 0 0) substrate previously cleaned by UHV prolonged heating. AFM shows that L-CVD SnO₂ thin films deposited on thermally oxidized Si(1 0 0) substrate after cleaning with ion bombardment exhibit evidently increasing rough surface topography with respect to roughness, grain size range and maximum grain height as the L-CVD SnO₂ thin films deposited on atomically clean Si substrate at the same surface chemistry (nonstoichiometry) reflect the higher substrate roughness after cleaning with ion bombardment.     

Particle‐in‐cell simulation of the effect of curved magnetic field on wall bombardment and erosion in a hall thruster

A curved, convex towards the channel bottom magnetic field is an important feature of an advanced Hall thruster that allows confining the plasma flow in the channel center, reducing the divergence angle of the ejected ion beam, and improving the discharge performance. In this article, the discharge behaviour of a Hall thruster in magnetic fields with different degrees of curvature is simulated with a particle‐in‐cell numerical method, and the effect of curved magnetic field on the ion bombardment and wall erosion and the associated mechanisms are studied and analysed. The results show that, as the curvature of the magnetic field increases, the propellant ionization becomes more confined at the channel center, the potential drop inside the channel decreases, and the acceleration region shifts outside the channel, which lead to the attenuation of the ion energy bombarding the wall and the deviation of the bombardment angle from the optimal sputtering angle. Conversely, the ion flux bombarding the wall near the channel exit increases. Nevertheless, the bombardment energy and angle are the dominant factors for the wall erosion, and the wall erosion rate clearly decreases with the increasing curvature of the magnetic field. These findings are closely related to the behaviour of electron conduction under a curved magnetic field; the relevant mechanisms are clarified in this article.     

Evaporative ion plating: process mechanisms and optimization

The basic discharge mechanisms pertinent to ion plating process are reviewed and some recent findings are highlighted, relating in particular to thermionically enhanced ion plating with an evaporative vapor source. By enhancing the discharge, the cathode sheath can approach collisionless conditions, which allows most of the energy to be transported to the substrate by ions. The energy distribution is also improved, this being significant if a critical energy E* is thought to be required in order to achieve high-quality coatings. It is suggested that E* is about 40 to 70 eV, and that higher bombarding energies may not necessarily improve coating quality, this being alternatively achievable by increasing the ionization efficiency. The role of metal vapors is outlined with reference to evidence from enhanced discharges that clusters of metal atoms exist in the vapor phase and that most of the ion current is transported to the substrate by the metal species. Further practical aspects are discussed such as the spatial distribution of bombardment intensity, which is shown to decrease exponentially with distance from the thermionic emitter used for discharge enhancement. It is suggested that positioning the thermionic emitter in close proximity to the vapor source will provide a more consistent ratio between energetic bombardment effects and vapor arrival rates throughout the deposition volume     

Influence of surface topography on the secondary electron yield of clean copper samples

Secondary electron yield (SEY) due to electron impact depends strongly on surface topography. The SEY of copper samples after Ar-ion bombardment is measured in situ in a multifunctional ultrahigh vacuum system. Increasing the ion energy or duration of ion bombardment can even enlarge the SEY, though it is relatively low under moderate bombardment intensity. The results obtained with scanning electron microscopy and atomic force microscopy images demonstrate that many valley structures of original sample surfaces can be smoothed due to ion bombardment, but more hill structures are generated with stronger bombardment intensity. With increasing the surface roughness in the observed range, the maximum SEY decreases from 1.2 to 1.07 at a surface characterized by valleys, while it again increases to 1.33 at a surface spread with hills. This phenomenon indicates that hill and valley structures are respectively effective in increasing and decreasing the SEY. These obtained results thus provide a comprehensive insight into the surface topography influence on the secondary electron emission characteristics in scanning electron microscopy.     

Step edge sputtering yield at grazing incidence ion bombardment

The surface morphology of Pt(111) was investigated by scanning tunneling microscopy after 5 keV Ar+ ion bombardment at grazing incidence in dependence of the ion fluence and in the temperature range between 625 and 720 K. The average erosion rate was found to be strongly dependent on the ion fluence and the substrate temperature during bombardment. This dependence is traced back to the variation of step concentration with temperature and fluence. We develop a simple model allowing us to determine separately the constant sputtering yields for terraces and for impact area stripes in front of ascending steps. The experimentally determined yield of these stripes--the step-edge sputtering yield--is in excellent agreement with our molecular dynamics simulations performed for the experimental situation.     

Microstructure of Bonding Zones in Laser Clad TiC-reinforced Coating

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A SIMS study of ion beam induced migration of nitrogen in thermally oxidized silicon

The potential use of thin silicon nitroxide films as gate dielectrics in VLSI MOS devices has motivated much recent work. The present study shows that positive ion bombardment, as encountered in sputter depth profiling or ion implantation, can induce considerable movement of nitrogen in thin thermal oxide films on silicon. Low energy N⁺₂ implants are performed in-situ in a SIMS apparatus and are subsequently depth profiled. The effect of implant dose and oxide thickness are examined and comparisons are made to films prepared by rapid thermal nitridation and LPCVD. Profiles obtained under O⁺₂, O^-, and Cs⁺ bombardment are also compared. SIMS depth profiles of implanted 200 Å oxides using positive ion bombardment show a depletion of nitrogen near the surface, a shoulder in the nitrogen concentration near the Si-SiO₂ interface, and a peak in this concentration at the interface. Negative ion bombardment did not induce a shoulder-peak structure at the interface. The implications of these results are discussed.     

Solid surface dependent layering of self-arranged structures with fibril-like assemblies of alpha-synuclein

In present work the formation of hybrid constructions composed of alpha-synuclein-based colloidal solutions on various solid surfaces (silica coated Si, mica, CaF₂ and KBr) is investigated by scanning probe microscopy, spectrocopic ellipsometry, Fourier transformed infrared spectroscopy and vibrational circular dichroism. Prior to the modification of the solids, the proteins were intentionally fibrilled under special conditions. It is proved that the multi-component coatings are self-arranged on the solid substrates. Depending on the substrate material, the interface films consisting of individual biomolecules can be detected on the solid surfaces. The coatings with fibril-like alpha-synuclein objects can be obtained on solid surfaces with negligible or comparatively thick interface films. The results are interpreted in terms of the charged surface-controlled electrostatic interaction between the substrate and the biomolecules. Solubility of solids is considered in this interpretation.     

ZnS和MgF2薄膜的离子辅助淀积

用Ar离子辅助制备了ZnS和MgF_2薄膜,依据滤光片吸潮波长漂移的测量,MgF_2膜的聚集密度大约从未轰击时的0.8上升到轰击后的0.9～0.95,实验发现,高能离子轰击(>1keV),膜层的吸收散射损耗增加,而低能离子轰击(<700eV)可以保持优良的光学性质,并显著地增加膜层的牢固度,这对于温度敏感的基底制备耐久薄膜是一个重要的应用.     

Field ion and scanning tunnel microscopy studies of surface and bulk defects in carbon and silicon

Complex study of surface and bulk defects was performed by field ion and scanning tunnel microscopy. Specimens were irradiated by 20-to 50-keV He⁺, Ar⁺, and Bi⁺ ions at room temperature. The irradiation fluences were between 10¹⁸ and 10²⁰ ion m⁻². Calculated parameters of depletion zones and atomic displacement cascades were compared with theoretical estimates. It was shown that controlled ion bombardment of material surface is an effective tool for fabricating field-emission cathodes for vacuum microelectronics.     

低能氩离子束对多孔铝阳极氧化膜表面的刻蚀效应研究

用低能氩离子束(Ar⁺)处理了多孔铝阳极氧化膜(AAO)表面.扫描电子显微镜和原 子力显微镜结果表明，Ar⁺束刻蚀不仅可以有效地去除AAO反面阻挡层，还可使A AO表面产生多种特殊的形貌，如采用倾角入射可使其表面产生波纹，倾角入射同时旋转样品 台，可实现表面抛光.并结合Bradley和Harper提出的无定形材料表面波纹的形成和演化理论 解释了AAO表面波纹的特征. 关键词： 多孔铝阳极氧化膜 离子束刻蚀