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European Microscopy Congress 2016: Proceedings || An in-situ Low Energy Argon Ion Source for Local Surface Modification
摘要： A new in-situ low energy ion source for surface modification of a sample surface has been designed. The source is based on the principle of low energy ion bombardment from a beam of ions such as Ar+, N+, or He+ can be used for a local modification of the sample surface. Typical energies are in the range 10 - 100 eV, covering the interaction types from chemical reaction to ion etching and to ion implantation. The source is based on the following principle: electrons from a filament are accelerated towards a grid by a potential difference between the filament and the grid. The electrons enter a gas-filled region between the grid and the sample, where they ionize the gas. The ions are then accelerated towards the sample by a potential difference between the grid and the sample. The source produces a static beam of ions with a selectable energy of 10-100 eV and a full width half maximum (FWHM) of 7.1 um. This corresponds to a central ion current density of 0.019 nA/um2 at 100 eV, which is very similar to the current density at 100 eV of a regular ICP source. In this way, the sample area that is affected by the low energy ions can be more or less defined by the applied bias voltage. The first application can be polishing the top surface of a TMD laminate produced by CVD, or improvement of and LPE surface prepared by ICP. An example of the interaction with the beam is shown in Figure 1, where a native oxide on Si has been removed in 25 seconds, using 100 eV Ar+ ions.
关键词： Ar+,surface modification,low energy ion source,chemical reaction,FWHM,native oxide removal,ion etching,ICP,current density,static beam,N+,ion bombardment,TMD,He+,LPE,ion implantation,in-situ,gas ionization,filament,grid,CVD
更新于2025-09-19 17:15:36
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Reconfigurable H‐plane waveguide phase shifters prototyping with additive manufacturing at K‐band
摘要： This work presents the design and manufacturing of a K-band reconfigurable phase shifter completely implemented in waveguide technology for reduced insertion loss, good matching, and large phase shifting range. The device is based on the combination of a short slot coupler and two tunable reactive loads implemented as a section of short-circuited waveguide where an adjustable metallic post is inserted. Three prototypes of this design have been manufactured using different techniques (conventional computer numerical control machining, a low-cost fused filament fabrication technique and direct metal laser sintering) in order to assess its performance for different applications. The prototypes have been characterized experimentally and the achieved results are evaluated and compared. The proposed phase shifter, since it is fully developed in waveguide technology, eliminates the need of adding transitions to planar structures in order to integrate lumped components like pin diodes or varactors. Therefore, this device has a great potential in high-power beam steering phased arrays.
关键词： reconfigurable,selective laser sintering,additive manufacturing,waveguide,fused filament fabrication,phase shifter
更新于2025-09-19 17:13:59
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The Effect of Different Filament Arrangements on Thermal and Optical Performances of LED Bulbs
摘要： The influences on thermal and optical performances of light emitting diode (LED) bulbs with three different filament arrangements are investigated in detail. The average junction temperature, temperature of the surface of the bulb, and luminous flux of three samples all increased with increasing power. The thermal performance test results show that between the average junction, temperature and power were linear. The junction temperatures of the three samples at a power of 3.5 W were 102.48, 98.46, and 88.88 °C. The optical performance test results revealed that the luminous flux and efficiency in the two vertical filament arrangements were closely related to each other and higher than that of the horizontal filament arrangement. A numerical model of LED filament bulbs was established by the Floefd 17.2 software for analyzing the temperature distribution of the cross section and the gas flow path inside the bulb. The simulation results illustrated that the average temperatures of three samples were 105.88, 101.83, and 96.12 °C. Additionally, the gas flow inside the bulb of the two vertical filament arrangements was subject to forming a thermal cycle during operation work more than that of the horizontal filament arrangement. As a result, the flexible spiral LED filament bulb is feasible as a new light source.
关键词： optical,filament arrangement,led filament bulb,thermal
更新于2025-09-16 10:30:52
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6 GHz electromagnetic wave guiding along a femtosecond laser plasma filament
摘要： To study the electromagnetic (EM) wave guiding performance of the plasma filament generated by the intense femtosecond (fs) laser pulse, a 3D physical model of the wave-plasma interaction is built and discussed with the commercial simulation software XFDTD. Then, an experiment is conducted to verify the EM wave guiding performance of the fs laser plasma filament. Our investigation illustrates that the 6 GHz EM wave can propagate along the fs plasma filament, making the EM field enhance out of the rectangular waveguide and attenuate in the rectangular waveguide. Besides, the filament can cause 4.74 dB enhancement of the wave energy relative to freely propagating the signal. Furthermore, the experimental result indicates that the guiding performance of the plasma filament on the TE polarization wave is better than that on the TM one, which is consistent with the theoretical result. For TE polarization wave, the plasma filament can reduce the microwave signal in the waveguide, which is lesser than that of the Cu wire in the experiment. The research results confirm that the fs laser plasma filament can guide the EM wave with a better performance relative to freely propagating the signal.
关键词： waveguide,guiding,plasma filament,femtosecond laser,EM wave
更新于2025-09-12 10:27:22
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Controlled Growth of Silver Nanoparticles on Indium Tin Oxide Substrates by Plasma-Assisted Hot-Filament Evaporation: Physical Properties, Composition, and Electronic Structure
摘要： High-density silver (Ag) nanoparticles of controllable size and uniformity were used to enhance conductivity and luminance efficiency in an organic light emitting diode device. As part of this experiment, Ag nanoparticles were deposited on indium tin oxide (ITO) substrates by using plasma-assisted hot-filament evaporation. These nanoparticles mainly exhibited spherical grain morphology, with average diameters ranging between 7.5 and 45.7 nm depending on substrate temperature; the size of Ag nanoparticles are known to increase with rises in substrate temperatures up to 250°C, a phenomenon attributable to thermally induced surface diffusion. With regards to the optical spectra, the characteristics of the localised surface plasmon resonance were directly affected by changes in the physical properties of the Ag nanoparticles, such as diameter and interparticle distance. The X-ray photoemission spectroscopy results revealed the formation of a shell layer of silver oxide on the Ag nanoparticles. This resulted in a significant effect on the optical and electrical properties of the Ag nanoparticles/ITO. The highest density of Ag nanoparticles deposited at 80°C were associated with the lowest sheet resistance and work function at 7.45 Ohm/square and 3.97 eV, respectively, while increases in the oxide formation significantly increased the sheet resistance and work function up to 200°C. The effects of substrate temperature on the morphology, structure, as well as optical and electrical properties of the deposited Ag nanoparticles on ITO are discussed in further detail in this report.
关键词： Substrate temperature,Silver,Surface plasmon resonance,Work function,Silver oxide,Nanoparticles,Plasma-assisted hot-filament evaporation
更新于2025-09-12 10:27:22
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Experimental and analytical evaluation of the acoustic radiation of femtosecond laser plasma filament sound sources in air
摘要： Plasma ?laments in air induced by femtosecond laser pulses lead to the generation of strong shock waves. This letter presents a systematic study, both experimental and theoretical, of the acoustic radiation by femtosecond laser-generated ?laments. A theoretical model is developed based on the experimental results and is used to evaluate the directivity of the ?lament’s acoustic radiation within and beyond the audible frequency range. It is shown that the acoustic directivity of plasma ?laments can be derived from the model of a weighted acoustic line source, consisting of elementary point sources with N-shaped excitation.
关键词： acoustic radiation,plasma filament,femtosecond laser,directivity,shock waves
更新于2025-09-12 10:27:22
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Formation Dynamics of Excited Neutral Nitrogen Molecules inside Femtosecond Laser Filaments
摘要： Nitrogen molecules are promoted to excited neutral states during femtosecond laser pulse filamentary propagation in atmosphere, leading to a characteristic UV fluorescence. Using a laser-induced fluorescence depletion technique, we measure the formation dynamics of these excited neutral nitrogen molecules with femtosecond time resolution. We find that the excited neutral molecules are formed in an unexpected ultrafast timescale of ～4 ps at 1 bar and ～120 ps at 30 mbar pressure. From this observation we deduce that the excitation of neutral N2 occurs via multiple collisions with hot free electrons. Numerical simulations based on rate equations reproduce well this ultrafast formation time and its dependence on gas pressure, and thus support this interpretation.
关键词： electron impact excitation,femtosecond laser,plasma filament,UV fluorescence,nitrogen molecules
更新于2025-09-12 10:27:22
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Effect of Different Bonding Materials on Flip-Chip LED Filament Properties
摘要： This article researches the effect of Sn-based solder alloys on flip-chip light-emitting diode LED (FC-LED) filament properties. SEM images, shearing force, steady-state voltage, blue light luminous flux, and junction temperature were examined to demonstrate the difference between two types of FC-LED filaments welded with two solders. The microstructure surface of Sn90Sb10 filament solder joints was smoother and had fewer voids and cracks compared with that of SAC0307 filament solder joints, which indicates that the Sn90Sb10 filaments had a higher shearing force than the SAC0307 filaments; moreover, the average shearing force was beyond 200 gf (standard shearing force). The steady-state voltage and junction temperature of the Sn90Sb10 solder-welded FC-LED filament were lower, and the Sn90Sb10 filament had a relatively higher blue light luminous flux. If high reliability of the solder joints and better photoelectric properties of the filaments are required, this Sn90Sb10 solder is the best bonding material for FC-LED filament welding.
关键词： reliability,lead-free solder,photoelectric properties,FC-LED filament
更新于2025-09-12 10:27:22
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Improved resistive switching performance in Cu-cation migrated MoS2 based ReRAM device incorporated with tungsten nitride bottom electrode
摘要： The resistive switching characteristics of sputtered deposited molybdenum disulphide (MoS2) thin film has been investigated in Cu/MoS2/W2N stack configuration for Resistive Random Access Memory (ReRAM) application. The benefits of incorporating tungsten nitride (W2N) as a bottom electrode material were demonstrate by stability in operating voltages, good endurance (103 cycles) and long non-volatile retention (103 s) characteristics. Resistive switching properties in Cu/MoS2/W2N structure are induced by the formation/disruption of Cu conducting filaments in MoS2 thin film. Ohmic law and space charge limited current (SCLC) are observed as dominant conduction mechanism in low resistance state (LRS) and high resistance state (HRS) respectively. This study suggests the application of MoS2 thin films with W2N bottom electrode for next generation non-volatile ReRAM application.
关键词： Conducting filament,Resistive switching,Molybdenum disulphide,Thin films,Tungsten nitride
更新于2025-09-10 09:29:36
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Estimation of the Temperature of the Current Filament that Forms upon Switching in GeSbTe
摘要： The current–voltage characteristics of thin-film samples of the GeSbTe system are measured in the current control mode. Voltage oscillations observed after switching are investigated. It is shown that these oscillations can be associated with the formation of a hot current filament and its gradual cooling. The size and temperatures of the current filament are estimated. It is shown that the characteristic temperature in the hot current filament corresponds to the temperature of the phase transition to the crystalline state.
关键词： phase transition,GeSbTe,voltage oscillations,switching effect,current filament
更新于2025-09-10 09:29:36