Tailoring optical response in nanostructured bilayers: Effects of surface roughness and layer thickness on NbN/Nb and TiN/Ti

2023-10-13T13:24:43-06:00

Numerical calculations were performed on NbN/Nb and TiN/Ti nanostructured bilayers. Discrete dipole approximation
implemented in the DDSCAT code was utilized. In order to design a TUC (Target Unit Cell) with realistic surfaceroughness
pattern, Atomic Force Microscope images of 100 ±10 nm Nb thin films were used. The optical properties of nanostructured bilayers (60-100 nm thickness with a ±10 nm surface roughness) were calculated, keeping the interface
between the layers as smooth flat surfaces. For the NbN/Nb nanostructure with a thickness between 100 ±10 nm, and 70 ±10 nm, in a wavelength range between 200 and 350 nm, the reflectance and absorptance show a nearly flat spectrum
with an intensity of 20% and 80%, respectively. For larger wavelengths, absorptance decays smoothly. In contrast, for the 60 ±10 nm bilayer, the absorptance decays faster. For the TiN/Ti nanostructure, at 415 nm, a relative maximum in the reflectance, and a minimum in absorptance, are observed. The critical value of the absorbed light spectra begins to shift to higher wavelengths as the thickness of the TiN layer increases. We demonstrate that adding a rough nitride layer on top of its metallized layer drastically modifies the optical response of the nanostructured bilayer, an interesting result for
plasmonics and nanoelectronics applications.

Method for measuring the setting process of cement-water mixtures by electrical impedance

2024-01-11T10:11:58-06:00

The setting and hardening of cement paste can be taken as the progressive hydration reaction of cement. This paper reports the findings on setting time of cement paste at early hydration by using a novel method named relative electrical impedance (REI). The novel REI method measures the relative electrical impedance between electrodes (ring shaped) embedded in the cement paste. REI measurements were conducted on cement paste samples with a water-cement ratio of 1:2 over 24 hours. REI measurements were compared with VICAT and heat latent methods for indirect validation. It was found that the proposed REI technique determined the 4 periods of the setting time process (sleeping, hydration, deceleration, and diffusion) and allowed the measurement of the sleeping period in detail. It was concluded that the novel REI method could be used as a new method to measure the setting time of cement paste in early hydration.

Superficies y Vacío

Tailoring optical response in nanostructured bilayers: Effects of surface roughness and layer thickness on NbN/Nb and TiN/Ti

Method for measuring the setting process of cement-water mixtures by electrical impedance