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In situ Photoluminescence Study of Plasma Effects on Passivation of Crystalline Silicon Coated with Aluminum Oxide
摘要： A degradation of crystalline silicon surface passivation provided by aluminum oxide (Al2O3) is generally observed after plasma processes, e.g., deposition of amorphous silicon nitride. To minimize such detrimental effect, a better understanding of the interaction between plasma species and the Al2O3 layer is required. Using in situ photoluminescence, the passivation quality of as-deposited and annealed crystalline silicon wafers coated with Al2O3 grown by atomic layer deposition is characterized in real time during argon-hydrogen plasma exposure. The photoluminescence intensity of as-deposited samples instantly steps up after the plasma ignition, and then it gradually decreases as a function of plasma exposure time. However, only degradation of photoluminescence signal can be found if the samples are annealed prior to the plasma treatment. The interaction between vacuum UV light from plasma and different types of chemical bonds in the Al2O3 layer is proposed to explain the obtained results. Understanding the mechanisms and root cause leading to different behavior between as-deposited and annealed samples under plasma exposure is a first step toward redesigning the process flow for better surface passivation.
关键词： in situ photoluminescence,plasma exposure,aluminum oxide,surface passivation
更新于2025-09-23 15:23:52
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Surface chemical states of gold nanoparticles prepared using the solution-plasma method in a CsCl aqueous solution
摘要： In this study, gold nanoparticles (AuNPs) prepared in a 5 mM CsCl aqueous solution using the solution‐plasma method are characterized via transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy with synchrotron radiation (SR‐XPS). The particle diameter is measured over the process time via TEM. During the solution‐plasma process, small particles of 2.1 to 2.2‐nm diameter are generated in the CsCl aqueous solution; these particles then enlarge via Ostwald ripening over time until they reach an equilibrium size of ~13 nm after 36 days. In addition, the surface chemical states of the AuNPs are characterized at different depths via SR‐XPS. The SR‐XPS measurements obtained using incident X‐ray energy (hν) of 945.0 eV revealed that Cs─Au, Cl─Au, and Cs─Cl─Au bonds are present 1.2 nm below the surface. The measurements obtained at an incident X‐ray energy of 2515.0 eV showed that Cs─Cl─Au bonding is also present 2.5 nm below the surface, indicating that Cs and Cl strongly interact with Au. The TEM and SR‐XPS measurements revealed that 2 processes occur cyclically during the growth process via Ostwald ripening: (i) the Cs and Cl in the aqueous solution adsorb on the AuNP surface and (ii) Au atoms subsequently bond to the AuNPs surface.
关键词： solution‐plasma method,TEM,gold nanoparticles,XPS,surface chemical states
更新于2025-09-23 15:23:52
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Time-and-Space Resolved Cathode Plasma Expansion Velocities in Magnetically Insulated Coaxial Diode With a Metal-Dielectric Cathode
摘要： Time-and-space resolved cathode plasma expansion velocities in magnetically insulated coaxial diodes (MICD) with edged cathodes made of bronze dielectric, bronze, and graphite have been compared through optical diagnosis. The voltage and current of the diode pulse of 260 ns are about 400 kV and 2.8 kA, respectively. The axial and radial expansion velocities of the cathode plasma were obtained through the angled lateral view by utilizing high-speed framing camera combined with the digital image processing methods. In addition, the evolution of the cathode and collector plasmas was visible firstly on the front view at the same time. The bronze-dielectric cathode not only showed low expansion velocity of about 0.5 cm/μs but also had other superior characteristics indicated by the strong emission capability, the fast plasma formation and the uniform plasma distribution. Thereby, the metal–dielectric cathode is a good candidate for applications in a long-pulsed MICD.
关键词： Bronze-dielectric cathode,plasma expansion velocities,high-speed framing camera (HSFC),magnetically insulated coaxial diode (MICD)
更新于2025-09-23 15:23:52
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CVD Diamond
摘要： Diamond has the most extreme properties in mechanical, chemical and physical domain. There are many methods to manufacture synthetic diamond. Diamond layers can be deposited on various materials by many processes. The most robust and preferred method is chemical vapour deposition. A variety of researches have been performed on CVD coatings, and a range of developments has come forth starting from initial publications to the latest results. The process parameters of different CVD techniques have been discussed with technical limitations. Flow rate, applied power, increased pressure and temperature range are important parameters for the deposition of CVD diamond.
关键词： Plasma arrangement,Hot filament,Chemical vapor deposition
更新于2025-09-23 15:23:52
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Silver nanoparticles with reduced graphene oxide for surface-enhanced vibrational spectroscopy of DNA constituents
摘要： Composite of silver nanoparticles with reduced graphene oxide flakes is proposed for surface enhanced vibrational spectroscopy, particularly for detection of adenine and thymine as constituents of deoxyribonucleic acid. Composite was formed by original method implying simultaneous reduction of silver ions and graphene oxide by discharge plasma at the gas–liquid interface. Combination of nanosized silver with reduced graphene oxide provided greater enhancement of Raman light scattering and infrared light absorption in comparison with separately used components. Addition of the composite to water solutions of adenine and thymine allowed detection of these analytes at micromolar concentrations. Composite of nano-silver with reduced graphene oxide can be prospective for surface enhanced spectroscopy as an alternative to the expensive lithographically prepared noble metal substrates.
关键词： Adenine,Surface Enhanced InfraRed Absorption (SEIRA),Thymine,Reduced graphene oxide,Discharge plasma,Silver nanoparticles,Surface Enhanced Raman Scattering (SERS)
更新于2025-09-23 15:23:52
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Low-damage nitrogen incorporation in graphene films by nitrogen plasma treatment: Effect of airborne contaminants
摘要： Graphene films grown on copper by chemical vapor deposition were exposed to the late afterglow of a reduced-pressure N2 plasma sustained by microwave electromagnetic fields. X-ray photoelectron and Raman spectroscopies reveal extremely high incorporation of plasma-generated N atoms into the graphene film (N/C = 29%) while maintaining an unprecedentedly low-damage generation (D:G = 0.35-0.45) compared to the literature (0.5 to 2.5). The incorporation dynamics between graphene on copper and graphene on copper oxide are also compared and discussed. After transfer on SiO2/Si substrate, the N/C content decrease to only 6%. This reveals that a large part of the N atoms are weakly bonded to the graphene surface. Most of the nitrogen incorporation seems linked to the functionalization of weakly bonded hydrocarbons initially adsorbed from air exposure or carbon-nitrogen structures arising from plasma-surface interactions.
关键词： X-Ray photoelectron spectroscopy,Raman spectroscopy,graphene,downstream plasma treatment,N-incorporation
更新于2025-09-23 15:23:52
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Double-exponential kinetics of binding and redistribution of the fluorescent dyes in cell membranes witness for the existence of lipid microdomains
摘要： New technique of detecting lateral heterogeneity of the plasma membrane of living cells by means of membrane-binding fluorescent dyes is proposed. The kinetics of dye incorporation into the membrane or its lateral diffusion inside the membrane is measured and decomposed into exponential components by means of the Maximum Entropy Method. Two distinct exponential components are obtained consistently in all cases for several fluorescent dyes, two different cell lines and in different types of experiments including spectroscopy, flow cytometry and fluorescence recovery after photobleaching. These components are attributed to the liquid-ordered and disordered phases in the plasma membrane of studied cells in their dynamic equilibrium.
关键词： Kinetics,Maximum Entropy Method,Decomposition,Lipid phases,Plasma membrane heterogeneity
更新于2025-09-23 15:23:52
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Enhanced sensor life using UV treatment of sulphur poisoned Pt-PtOx
摘要： In this work, we report a novel method for recovery of sulphur poisoned platinum/platinum oxide (Pt-PtOx) core-shell nanowire sensor using UV irradiation. The optimum core to shell thickness ratio and the operating conditions are the key factors to achieve a high-performance H2S sensor, described in this report. The fabricated core-shell nanowire sensor demonstrated response of 6.4% at 1 ppm H2S with detection limit of 10 ppb at 150°C operating temperature. The sensor undergoes prominent time-dependent poisoning at H2S exposure of 3 ppm when operated at 150°C due to sensor surface contamination by sulphur, later confirmed by XPS analysis. Ultraviolet light at two wavelengths, 365 nm, and 248 nm is investigated to recover the poisoned Pt-PtOx surface. UV irradiation at 248 nm for 5 minutes results in sensor recovery, confirmed by further H2S sensing characterization and XPS studies on the recovered sensor. To the best of our knowledge, this is one of the first reports on UV irradiation for recovery of sulphur poisoned metal-oxide surfaces.
关键词： sulphidation,recovery,plasma oxidation,UV irradiation,core-shell nanowire
更新于2025-09-23 15:23:52
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Enhanced optoelectronic performance of plasma electrolytic oxidized monocrystalline silicon using rGO incorporation
摘要： rGO/SiO2 composite coating was successfully prepared by plasma electrolyte oxidation (PEO) process on monocrystalline silicon (mc-Si) substrate. Investigating the effect of rGO incorporation into the SiO2 coating revealed that the addition of rGO leads to a significant increase in the photo-trapping ability due to the high specific surface area and excellent electron transfer efficiency. The PL intensity of the composite sample was found to decrease, which signified the suspension of the electron-hole pairs’ recombination. As a result, the photocurrent gain of the composite coating enhanced about 5.5 times. Likewise, the time-response switching featured an over two-fold increase for the rGO/SiO2 coating, impressively.
关键词： Semiconductors,Plasma electrolyte oxidation,Optoelectrical properties,Composite materials,rGO/SiO2 composite
更新于2025-09-23 15:23:52
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Nanoscale GaN Epilayer Grown by Atomic Layer Annealing and Epitaxy at Low Temperature
摘要： Heteroepitaxy with large thermal and lattice mismatch between the semiconductor and substrate is a critical issue for high-quality epitaxial growth. Typically, high growth temperatures (>1000 °C) are required to achieve high-quality GaN epilayers by conventional metal?organic chemical vapor deposition. In this study, the high-quality GaN heteroepitaxy is realized by atomic layer annealing and epitaxy (ALAE) at a low growth temperature of 300 °C. The layer-by-layer, in situ He/Ar plasma treatment at a low plasma power was introduced in each cycle of atomic layer deposition to contribute the e?ective annealing e?ect for signi?cant enhancement of the GaN crystal quality. The Penning e?ect is responsible for signi?cant improvement of the GaN crystal quality due to the incorporation of He into the Ar plasma. The high-resolution transmission electron microscopy, nano-beam electron di?raction, and atomic force microscopy reveal a high-quality nanoscale single-crystal GaN heteroepitaxy and a very smooth surface. The full width at half-maximum of the X-ray rocking curve of the GaN epilayer is as low as 168 arcsec. The low-temperature ALAE technique is highly bene?cial to grow high-quality nanoscale GaN epilayers for sustainable, energy-saving, and energy-e?cient devices including high-performance solid-state lighting, solar cells, and high-power electronics.
关键词： Atomic layer annealing,Atomic layer deposition,Gallium nitride,Atomic layer epitaxy,Plasma treatment
更新于2025-09-23 15:23:52