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- 2019
- polycrystalline ferrite-garnet
- magnetoplasmonic crystals
- magnetooptical effects
- deposition
- ion-beam methods
- sputtering
- plasmon resonance
- Physics
- Moscow Technological University
- Moscow State University
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Cu2ZnGe(S1-xSe x)4 – The challenge to synthesize single phase material
摘要： The variation of the band gap energy in Cu2ZnGeSe4 and Cu2ZnGeS4 from 1.4 eV to 1.7 eV, which is controlled by different S/(S+Se) ratios renders the Cu2ZnGe(S1-xSex)4 solid solution an interesting material for the application in multi-junction solar cells. Nevertheless, this system has a certain complexity due to the existence of different polymorphs. Cu2ZnGeSe4 crystallizes in the tetragonal kesterite type structure, whereas Cu2ZnGeS4 may crystallize in the tetragonal stannite or the orthorhombic wurtz-stannite type structure, respectively. To gain deeper insights into this complex system a systematic study of the solid solution series Cu2ZnGe(S1-xSex)4 was performed using polycrystalline material prepared by solid state reaction. The chemical analysis performed by wavelength dispersive X-ray spectroscopy showed remarkable inhomogeneities with different quaternary phases co-existing within one sample. Additionally, a wide variety of binary and ternary secondary phases as well as elemental Ge was observed. The variety of secondary phases is higher in S-rich samples than in Se-rich samples of the solid solution. Thus, synthesis of Cu2ZnGe(S1-xSex)4 mixed crystals with off-stoichiometric composition is readily accompanied by the formation of various secondary phases making it a difficult task to obtain single phase material.
关键词： Wavelength dispersive X-ray spectroscopy,Solid state reaction,Polycrystalline powders,Chalcogenides,Secondary phases,Copper zinc germanium selenide,Copper zinc germanium sulfide
更新于2025-09-11 14:15:04
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Nanocarbon colloid produced by electro-spark discharge in ethanol for seeding the substrates in MPACVD synthesis of polycrystalline diamond films
摘要： We produced a nanocarbon colloid by electro-spark discharge as substrate seeding for microwave plasma-assisted chemical vapor deposition (MPACVD) synthesis of micro- and nano-crystalline diamond films and solid free-standing microcrystalline diamond plates. The colloid was produced by a specially designed device via a pulse electro-spark discharge in ethanol. The nanocrystalline diamond films and polycrystalline plates that were grown were examined by optical, SEM and TEM microscopies and Raman spectroscopy.
关键词： MPACVD,electro-spark discharge,nanocarbon colloid,polycrystalline diamond films
更新于2025-09-10 09:29:36
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Handbook of Mechanics of Materials || Surface/Interface Stress and Thin Film Stress
摘要： Thin ?lm stress is critical for the reliability and electronic/optoelectronic properties of thin ?lm devices. In this chapter, we systematically discussed the effects of surface and interface stresses on the ?lm stress development during growth of polycrystalline ?lms at the initial and ?nal growth stage. We demonstrate that surface stress plays an important role at the initial stage of ?lm growth (island growth stage), and conventional stress analysis technology such as wafer curveture experiments may not be applicable at this stage. At the late stage of ?lm growth, we also show that adatom insertion into the grain boundaries is the primary mechanism of compressive stress development.
关键词： interface stress,Thin ?lm stress,adatom insertion,wafer curvature,grain boundaries,surface stress,polycrystalline ?lms
更新于2025-09-10 09:29:36
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New Advances in Hydrogenation Processes - Fundamentals and Applications || Hydrogenation of Polycrystalline Silicon Thin‐Film Transistors
摘要： In this chapter, the behavior of hydrogen (H) atoms in polycrystalline silicon (poly‐Si) thin film is investigated in detail in order to evaluate and improve the quality of hydrogenated poly‐Si thin films. Hydrogenation drastically improves the Hall effect mobility, whereas excessive hydrogenation tends to degrade it. The catalytic method is useful to inhibit excessive hydrogenation and damage suffered by the electric‐field acceleration of charged particle. The H‐termination of the dangling bonds at grain boundaries can be observed indirectly or directly by chemical etching and Raman microscopy. This H‐termination appeared as the 2000?cm‐1 local vibrational mode (LVM) in Raman spectra. The breaking of the Si–Si bonds by hydrogenation was detected as the 2100?cm‐1 LVM. In addition, the defects generated in the plasma process exhibit multiple fine LVMs after hydrogenation. Moreover, we investigated the hydrogenation of low‐temperature (LT) poly‐Si thin‐film transistors (TFTs) from the perspective of the gettering phenomenon. The most important parameter for effective hydrogenation using H gas annealing is the rate of cooling from 400°C.
关键词： Raman scattering,hydrogenation,thin film,polycrystalline silicon,thin‐film transistors
更新于2025-09-10 09:29:36
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Highly-oriented (104) polycrystalline α-Al2O3 transparent ceramics prepared by a templated grain growth method
摘要： Highly-oriented (104) polycrystalline α-Al2O3 transparent ceramics were prepared by a templated grain growth (TGG) method using A-plane single-crystal sapphire as the template. This is the first report, to best of our knowledge, on polycrystalline α-Al2O3 ceramics oriented to non-optical axes. XRD and SEM results indicate that samples with high oriented grains and high-density structure are prepared. Compared to random samples, the oriented samples exhibited an increase in the real in-line transmittance (at 650 nm) from ~23% to ~62%. Moreover, the transmission remains a high level as the wavelength shifts toward the UV range (< 300 nm). This method can be extended to other uniaxial materials without optical axes in order to produce polycrystalline ceramics with excellent optical transparency.
关键词： polycrystalline α-Al2O3,oriented,transparent ceramics,grain growth
更新于2025-09-10 09:29:36
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Polycrystalline diamond films with tailored micro/nanostructure/doping for new large area film-based diamond electronics
摘要： This paper describes processes developed to change two key electrical properties (electrical resistivity and carrier type) of ultrananocrystalline diamond (UNCD) to microcrystalline diamond (MCD) films. The results show that the electrical properties of the investigated polycrystalline diamond films depend on the grain size and plasma treated grain boundary networks interfaces and external films’ surfaces, in which hydrogen, fluorine or nitrogen can be incorporated to tailor electrical carriers-type to tune the electrical properties. Exploring the feasibility of modulating the resistivity of polycrystalline diamond films via tailoring of grain size, surface chemistry and nitrogen or fluorine incorporation into films’ grain boundaries and external surfaces may enable applications of these diamond films as active or heat dissipation layers on micro/nano-electronic devices. This work can open the pathway to enabling an industrial process for new diamond-based electronics, since polycrystalline diamond films can be grown with extreme uniformity on 300 mm diameter Si wafers, used in manufacturing of current Si-based micro/nano-electronic devices.
关键词： Nitrogen incorporation,Diamond-based electronics,Electrical properties,Plasma treatment,Fluorine incorporation,Grain size,Polycrystalline diamond films
更新于2025-09-10 09:29:36
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Epitaxial thin films as a model system for Li-ion conductivity in Li <sub/>4</sub> Ti <sub/>5</sub> O <sub/>12</sub>
摘要： Using an epitaxial thin-film model system deposited by pulsed laser deposition, we study Li-ion conductivity in Li4Ti5O12, a common anode material for Li-ion batteries. Epitaxy, phase purity, and film composition across the film thickness are verified employing out-of-plane and in-plane X-ray diffraction, transmission electron microscopy, time-of-flight mass spectrometry, and elastic recoil detection analysis, respectively. We find that epitaxial Li4Ti5O12 behaves like an ideal ionic conductor that is well described by a parallel RC equivalent circuit, with an ionic conductivity of 2.5·10-5 S/cm at 230 °C and an activation energy of 0.79 eV in the measured temperature range from 205 °C to 350 °C. Differently, in a co-deposited polycrystalline Li4Ti5O12 thin film with average in-plane grain size <10 nm, a more complex behavior with contributions from two distinct processes is observed. Ultimately, epitaxial Li4Ti5O12 thin films can be grown by pulsed laser deposition and reveal suitable transport properties for further implementation as zero-strain and grain boundary free anodes in future solid-state microbatteries design.
关键词： anode,polycrystalline,thin film,Li4Ti5O12,LTO,battery,epitaxial,PLD
更新于2025-09-10 09:29:36
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Fragmentation and stress diversification in diamond powder under high pressure
摘要： Studying the fragmentation and re?nement of diamond powder as well as the diversi?cation in the intergranular stress is crucial to produce a high-quality polycrystalline diamond. In this paper, using different micron-size diamond powders as the initial materials, the samples were compressed under different pressures at ambient temperature. The fragmentation behavior of the diamond powder was investigated by scanning electron microscopy and with a laser particle size analyzer. The results show that the fragmentation of diamond comprises three stages with increasing pressure: (i) fracturing of edges and corners, (ii) cracking of the crystal plane, and (iii) re?nement of particle disorder; the particle deformation tends to become relatively stable after a certain pressure. In situ high-pressure synchrotron X-ray diffraction was used to study the intergranular stress distribution under non-hydrostatic compression to 35.1 GPa. A heterogeneous stress distribution was found in compressed diamond bulk, in which under the highest load, the maximum stress reached 69.5 GPa, whereas the minimum stress was only 18.8 GPa.
关键词： diamond powder,fragmentation,polycrystalline diamond,high pressure,intergranular stress
更新于2025-09-10 09:29:36
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On-machine texturing of PCD micro-tools for dry micro-slot grinding of BK7 glass
摘要： While using diamond micro-tools for micro-grinding, tool re-clamping errors and low chip removal space from machining zone are the primary factors which cause large vibrations, higher grinding forces and poor surface quality. On-machine tool preparation and tool texturing prior to micro-grinding can reduce tool re-clamping error. It can further help to reduce the tool-workpiece contact area along with enhanced chip removal from the machining zone speci?cally essential during dry micro-grinding as usage of the cutting ?uid should be minimized or completely avoided for environmental aspects. In this study, end faces of polycrystalline diamond (PCD) micro-tools have been on-machine textured using micro electro-discharge machining (micro-EDM) process. Four types of textured tools are envisaged viz. tool with one micro-cavity at the center of the end face (T2), one micro-groove along the end face diameter (T3), two intersecting micro-grooves at the end face (T4) and four intersecting micro-grooves at the end face (T5). A new term “contact area ratio” is de?ned to explain the texture dimension on the end face of the micro-grinding tools. Performances of di?erent micro-textured tools (T2, T3, T4 and T5) with respect to a normal commercial tool (T1) in terms of grinding force, surface roughness and micro-slot quality are investigated for micro-slot grinding of BK7 glass. It is observed that micro-textured micro-grinding tool e?ciently serves the purpose of provisional chip collection in passive grinding areas of the tool whereas chip adhesion or wear on the active grinding areas signi?cantly gets reduced as compared to un-textured tools. Maximum reductions in the x and y direction forces are observed with tool type T5 compared to all other tool types. Reduction in z direction force is comparable for both tool types T2 and T3. Average surface roughness decreased from tool type T1 to type T2, T3 and up to tool type T4 whereas it again increased for tool type T5. The current study shows that textured micro-grinding tools are capable of reducing high normal forces, surface roughness and material dragging which are major concerns during micro-grinding with ?at-end poly-crystalline diamond tools.
关键词： Polycrystalline diamond tool,Micro-texture,Micro-grinding,BK7 glass,Surface roughness,Grinding force,Micro-EDM
更新于2025-09-09 09:28:46
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Core-Shell Electrospun Polycrystalline ZnO Nanofibres for Ultra-Sensitive NO2 Gas Sensing
摘要： This paper discusses the growth of polycrystalline, self-supporting ZnO nanofibres which can detect nitrogen dioxide (NO2) gas down to 1 part per billion (ppb), one of the smallest detection limits reported for NO2 using ZnO. A new and innovative method has been developed for growing polycrystalline ZnO nanofibres. These nanofibres have been created using core-shell electrospinning of inorganic metal precursor zinc neodecanoate, where growth occurs at the core of the nanofibres. This process produces contamination-free, self-supporting, polycrystalline ZnO nanofibres of the average diameter and grain size 50 nm and 8 nm respectively, which are ideal for gas sensing applications. This process opens up an exciting opportunity for creating nanofibres from a variety of metal oxides, facilitating many new applications especially in the areas of sensors and wearable technologies.
关键词： NO2 gas sensing,polycrystalline fibres,ZnO nanofibres,Electrospinning
更新于2025-09-09 09:28:46