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Energy-enhanced deposition of copper thin films by bipolar high power impulse magnetron sputtering
摘要： Bipolar Pulse High Power Impulse Magnetron Sputtering (BP-HiPIMS) was investigated and used in this work to control the ion bombardment process of growing thin films and to improve their structure and properties. Energy-resolving mass spectroscopy was used to investigate the effect of reverse target voltage on the ion energies and fluxes during BP-HiPIMS of a high-purity copper target, in argon gas. It was found that the reverse target voltage provides a wide range of ion energies and fluxes incident to the growing film, which, in turn, produce a wide variety of effects during the deposition process, improving the adhesion strength and influencing both surface and bulk properties. Fast ICCD imaging was used to investigate both HiPIMS and BP-HiPIMS plasma dynamics. The temporal and spatial distributions of plasma potential measurements were performed in order to explain the mechanisms for accelerating the ions. The topological, structural and mechanical properties of the deposited coatings were investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), thermal desorption spectroscopy (TDS), scanning electron microscopy (SEM), nanoindentation and scratch tests. The obtained results indicate an energy-enhanced deposition process during BP-HiPIMS, the deposited films being characterized by smooth surfaces, dense microstructure, small inert gas inclusions, high elastic strain to failure, scratch resistance and good adhesion to the substrate. These improvements in the films’ structure and properties may be attributed to the intense and energetic ion bombardment taking place during the deposition process. During BP-HiPIMS operation, there is no net increase in the deposition rate as compared to the monopolar regime due to the re-sputtering process.
关键词： Bipolar Pulse High Power Impulse Magnetron Sputtering (BP-HiPIMS),Tribology,Fast ICCD imaging,Ion energy distributions (IED)
更新于2025-09-04 15:30:14
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Synthesis of amorphous carbon nanofibers on a surface of commercial polymers under the action of a high power ion beam of nanosecond duration
摘要： The irradiation of various commercial polymers (chlorinated polyvinyl chloride, polyvinyl chloride, polyvinyl alcohol, polymethyl methacrylate) by a high-power ion beam of nanosecond duration has been investigated. The amorphous carbon nanofibers formation was detected on the surface of low-cost commercial polymers (chlorinated polyvinyl chloride, polyvinyl chloride) containing a catalyst under the high power ion beam irradiation at room temperature. Various iron compounds (organic and inorganic) were used as catalytic additions. The electron microscopy (scanning and transmission) with an energy dispersive analyzer and Raman spectroscopy were used to investigate the morphologies and structure of irradiated polymers. Carbon nanofibers (CNFs) had a most probable diameter in the range 50-90 nm and a maximum length of up to 10 μm. The maximum CNFs growth rate was estimated as 160 μm/μs. A possible growth mechanism for CNFs is discussed.
关键词： electron microscopy,amorphous carbon nanofibers,catalytic additions,Raman spectroscopy,high-power ion beam,commercial polymers
更新于2025-09-04 15:30:14
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Relativistic Backward-Wave Oscillator with Parallel Wave Interaction
摘要： We study operation of a backward-wave oscillator (BWO) in the regime of parallel amplification of rotating waves with different azimuth indices. It is shown that in the linear case, the use of the parallel wave interaction principle allows one to enhance the BWO gain significantly as compared with a classical backward-wave oscillator. An option for using parallel amplification in high-power sectioned amplifiers is proposed.
关键词： backward-wave oscillator,parallel wave interaction,high-power amplifiers,relativistic sources,microwave band
更新于2025-09-04 15:30:14
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A hydrophobic ultralow refractive-index silica coating towards double-layer broadband antireflective coating with exceptionally high vacuum stability and laser-induced damage threshold
摘要： We report the fabrication of nanoporous silica coatings with tunable refractive indices by a one-step base-catalyzed sol-gel process using tetraethoxysilane as the precursor, hexamethylisilazane as the modifier at ambient conditions. The advantages of the present method are inexpensive, etchant-free and without high temperature calcination treatment. Importantly, porosity of the coatings can be tunable by changing the monomer ratio of the starting solution, which makes them suitable for top layer of broadband AR coatings. The tri-wavelength broadband AR coating with the refractive indices of the bottom and top layers as 1.27 and 1.16 was achieved on a fused silica substrate, which possessed high transmittance of 99.6%, 98.0% and 99.3% at 351 nm, 527 nm and 1053 nm, respectively. Moreover, the double-layer coating showed significant stability, when tested with polydimethylsiloxane pollution in vacuum for a week. In addition, LIDT of the double-layer coating was up to ca. 19.0 J cm?2 at a 6.3 ns laser pulse of 351 nm wavelength. This double-layer AR coating possesses excellent broadband AR performance, high LIDT, and excellent vacuum stability, which can open a new avenue to explore applications in high-power laser systems.
关键词： Antireflective coating,Laser-induced damage threshold,High-power laser system,Sol-gel,Vacuum stability
更新于2025-09-04 15:30:14