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PVP-assisted thermal annealing of thin Au layer for creation of effective and reproducible SERS substrates
摘要： Creation of SERS substrate with the large active area and homogeneous distribution of hot spots is now one of the most important tasks in the field of SERS practical implementation. This problem has been solved by various techniques, but the most applicable of them are expensive due to highly technical nature. In this work, a simple alternative approach based on thermal annealing of sputtered Au layer has been proposed. Usually, the thermal annealing of the thin Au layer leads to the formation of gold clusters array with high plasmon efficiency but with too wide size distribution and highly disordered arrangement. To overcome this drawback the previous soaking of Au layer in the poly(vinylpyrrolidone) (PVP) solution was proposed, with the aim to affect clusters formation and achieve the more homogeneous distribution of created hot spots array. Annealed Au and Au-PVP thin layers were characterized by AFM, XRD, XPS, UV–Vis and Raman spectroscopy techniques. Present results indicate that the PVP treatment before thermal treatment significantly affect the growth of the clusters and provide the perspective way for increasing of SERS efficiency and reproducibility.
关键词： Thin gold film,SERS,Annealing,Reproducibility
更新于2025-09-23 15:23:52
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Screening Effect of Ultrathin Gold Films on Excitons in Monolayer WS2
摘要： Screening plays an important role in determining the energy levels and binding energies of excitons in two-dimensional (2D) semiconductors. However, the photoelectric properties of 2D materials deposited upon metal films are often assumed to remain unaffected by the screening effect. Herein, we derive the reflectance contrast spectra of monolayer WS2 on different thicknesses of ultrathin gold films by using the transfer matrix method, and investigate the screening effect of ultrathin gold films on excitons in monolayer WS2. We show that the exciton binding energy of the ground state gradually decreases as the gold film thickness increases due to the enhanced screening effect. Nevertheless, it may be due to the impact of free-electron scattering on the permittivities of gold films: exciton resonance energies of the ground state and the first excited state gradually increase as the gold film thickness increases, which are different from previously reported variation trend of exciton energy levels with the thickness of screening media of 2D materials. As a consequence, the electronic bandgap of the exciton only presents a small variation range of less than 4 meV with thickening of the gold film from 0.0 to 40 nm. These findings shed light on understanding to what extent the screening effect of gold films affects the excitons in 2D materials.
关键词： Ultrathin gold film,Transfer matrix method,Excitonic properties,Monolayer WS2,Dielectric screening effect
更新于2025-09-23 15:22:29
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Photochemical Method of Applying Gold Films on The Dielectric Surfaces
摘要： A method of photochemical application of gold films on the dielectric surfaces is offered. At this initially by dipping of sample in a solution of gold chloride the sorption layer of the solution is created on the surface then the drying process is carried out under direct sunlight. As the drying of the sorption layer the conditions are created for the formation of monovalent gold chloride having semiconducting properties that allows gold reducing photochemical reaction to take place. Carrying out the process at room temperature in the absence of a reducing agent simplifies a gilding technology. A study of photochemical gilding textile using the scanning electron microscope ISM-6490-LV (JEOL, Japan) is showed that the degree of transition of gold on the surface of a textile is greater than 97%.
关键词： Gold,Semiconducting properties,Reduction mechanism,Photochemical method,Gold film
更新于2025-09-23 15:19:57
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Improvement of ablation capacity of sapphire by gold film-assisted femtosecond laser processing
摘要： Sapphire is widely used in civilian and military equipment owing to its superior optical and mechanical properties. Femtosecond laser has been demonstrated to be an effective tool to process sapphire material. However, the direct processing of sapphire by femtosecond laser still meets some challenges, such as poor ablation morphology and low laser energy absorption. In this work, femtosecond laser processing of sapphire coated with a 12-nm-thick gold film (Au-coated sapphire) has been investigated. The experimental results have revealed that the ablation morphology of Au-coated sapphire has been improved, featuring fewer molten materials and thermal cracks, as well as regular crater shape and uniform periodic surface structures. It has also been found that, under 100 shots condition, the threshold fluence of Au-coated sapphire is reduced by about 56% compared to that of uncoated one. Meanwhile, the incubation effect of Au-coated sapphire is stronger than that of uncoated one. We also illustrate that the material removal rate of Au-coated sapphire is increased up to about two times higher than that of uncoated one. In order to reveal the effective mechanism of the gold film in the laser processing of sapphire, the energy transfer process among incident photons, free electrons and sapphire lattice phonons was studied. Our study provides a guidance for improving the laser ablation capacity of sapphire.
关键词： Gold film,Sapphire,Material removal rate,Ablation morphology,Femtosecond laser processing
更新于2025-09-19 17:13:59
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Ultrafast Broadband Diagnostics of the Filling of the s Band at the Two-Photon Femtosecond Laser Excitation of a Gold Film
摘要： The transmission of near infrared femtosecond laser pulses (wavelength of 800 nm) and supercontinuum radiation (300–750 nm) generated by them through a 50-nm gold film immersed in water has been experimentally studied at the power of focused laser radiation in the range of 1–10 GW. An increase in the excitation intensity is accompanied by the blueshift of the edge of the extinction band of the film, which is attributed to the filling of electronic states of the s band with a low density of states caused by two-photon interband transitions from d bands with a high density of states.
关键词： supercontinuum radiation,gold film,ultrafast broadband diagnostics,s band filling,two-photon femtosecond laser excitation
更新于2025-09-11 14:15:04