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Spectrophotometric Characterization of Thin Copper and Gold Films Prepared by Electron Beam Evaporation: Thickness Dependence of the Drude Damping Parameter
摘要： Copper and gold films with thicknesses between approximately 10 and 60 nm have been prepared by electron beam evaporation and characterized by spectrophotometry from the near infrared up to the near ultraviolet spectral regions. From near normal incidence transmission and reflection spectra, dispersion of optical constants have been determined by means of spectra fits utilizing a merger of the Drude model and the beta-distributed oscillator model. All spectra could be fitted in the full spectral region with a total of seven dispersion parameters. The obtained Drude damping parameters shows a clear trend to increase with decreasing film thickness. This behavior is discussed in the context of additional non-optical characterization results and turned out to be consistent with a simple mean-free path theory.
关键词： optical constants,gold,copper,ultrathin metal films,thickness dependence
更新于2025-11-21 11:01:37
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Time-fractional subdiffusion model for thin metal films under femtosecond laser pulses based on Caputo fractional derivative to examine anomalous diffusion process
摘要： In this paper, the non-Fourier effects are examined in thin metal films exposed to femtosecond laser pulses. For the first time, the time-fractional subdiffusion model is presented based on the Caputo fractional derivative to examine the anomalous diffusion process in nano-scale metal films. The fractional heat conduction equation is solved numerically, using the finite difference method based on implicit scheme and the numerical results are compared to experimental data. The comparison implies that the numerical results well coincide with experimental data, proving the accuracy and suitability of fractional model to capture thermal behaviors of thin metal films heated by short-pulse laser. Furthermore, the results of time-fractional model are compared to other models including parabolic and hyperbolic two-step models. Having compared, one can be found is that the fractional model is more reliable than other models, because its results are well matched with experimental data. The use of Fourier’s law in parabolic and hyperbolic two-step model leads to deviation from experimental data which can be addressed upon applying the proposed time-fractional model in this work. Moreover, the presented time-fractional model can be effectively utilized for studying the heat transport in thin metal films under laser pulses as well as the laser heating process and its applications in engineering. Ultimately, the effect of changes in various parameters such as order of fractional derivative, laser pulse duration, metal materials (gold and chromium), gold film thickness, relaxation time and absorption depth of laser pulses are investigated on temperature response of thin metal films.
关键词： Time-fractional subdiffusion model,Short-pulse laser,Thin metal films,Caputo fractional derivative
更新于2025-09-23 15:19:57
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Technological and optical methods for increasing the spatial resolution of thermochemical laser writing on thin metal films
摘要： Various techniques, effects, and factors are examined that enable one to increase the spatial resolution of thermochemical direct laser writing on thin metal films. A few specific conditions of experimental laser processing with the focused beam of a CW green laser are investigated therewith. One of the goals of this work was to find a suitable metal and its thickness that would make it possible to implement the through-oxidation regime. When properly adjusting a value of laser exposure, this regime was found to be very useful for increasing the spatial resolution of the laser writing. This is due to bleaching of an oxidized film near the peak of a focused laser spot. Apart from the experimental results concerning the technology of laser processing of the metal films, in this work, there are also considered some ways of reducing a focused spot size used for the direct laser writing.
关键词： Diffractive structures,Spatial resolution,Non-destructive through-oxidation,Metal films,Thermochemical laser writing
更新于2025-09-16 10:30:52
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Plasmonics in Atomically Thin Crystalline Silver
摘要： We report on the fabrication of few-atomic-layer-thick wafer-scale crystalline silver films, along with the observation of plasmons in the near-to-mid infrared spectral regions upon lithographic structuring. Our measured optical spectra reveal narrow plasmons (quality factor ~ 4), further supported by a low sheet resistance comparable to bulk metal in few-atomic-layer silver films down to 7 Ag(111) monolayers. Good crystal quality and plasmon narrowness are obtained despite the addition of a thin passivating dielectric, which renders our samples resilient to ambient conditions.
关键词： 2D materials,ultrathin plasmonics,2D plasmonics,atomically thin silver,crystalline metal films
更新于2025-09-16 10:30:52
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Femtosecond Laser Micromachining of Metal Thin Films
摘要： In this paper the possibilities of femtosecond laser micromachining of thin-film titanium coatings for elements of microelectronics and optoelectronics are considered. Using pulsed laser deposition in vacuum (wavelength λ = 1030 nm, pulse repetition frequency f = 10 kHz, Emax pulse energy ≈ 150 μJ, pulse duration τ ≈ 280 fs), a thin-film titanium coating was obtained on the surface of the quartz substrate. An example of the formation of an element of a given geometry by selective laser ablation of areas of a deposited metal coating is shown.
关键词： ultrashort laser pulses,precision micromachining,laser ablation,thin metal films
更新于2025-09-12 10:27:22