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In this work, an efficient method is reported for creating a metal nanoparticle (silver) / Si composite structure consisting of a vertical array of silicon nanowires (SiNWs) decorated with silver metal nanoparticles. A two-stage metal-assisted etching method is employed to obtain SiNWs and Silver (Ag) metal nanoparticles are decorated on the SiNWs using the electroless deposition method. It allows the good coverage of silver metal nanoparticles over SiNWs. Scanning Electron Microscopy (SEM) analysis revealed that Ag was covered with SiNWs. High-work function metal nanoparticles such as Ag nanoparticles on SiNWs have been utilized in different applications such as photovoltaics and sensors. The size of SiNWs is determined through the Raman shift. The silicon optical phonon peak showed an increase in redshift and a decrease of full-width at half maxima with a decrease in diameter due to the quantum confinement. The Electron Field Emission (EFE) characteristics of the Ag-decorated SiNW films were studied based on the current-voltage measurements and analyzed using the Fowler-Nordheim (F-N) equation. The low turn-on field is obtained through the Ag metal nanoparticles which have wider applications in low-power operational devices. [ABSTRACT FROM AUTHOR]

One of the most important parameters in Raman spectroscopy is the wavenumber (Raman shift), which is calculated from the difference between the excitation and Raman scattering absolute wavenumbers. Because the observed wavenumbers are strongly dependent on the spectrometer and measurement conditions, it is essential to calibrate the system by using a well‐characterised material. We therefore reliably estimated the wavenumbers and evaluated their uncertainty for the peaks of benzonitrile and cyclohexane by using a HeNe laser and Raman‐scattered light calibrated with Ne/Ar emission lines. We considered the uncertainties originating from the fitting and repeatability of both the Ne/Ar emission lines and the Rayleigh/Raman‐scattered lights, as well as the unstabilised HeNe laser, and the pixel and spectral resolutions. We also considered the uncertainty originating from the differences in results among the grades and manufacturers (four for benzonitrile and seven for cyclohexane). The estimated wavenumbers of 12 peaks for benzonitrile and 11 peaks for cyclohexane were comparable with those described in ASTM E1840 with an expanded uncertainty from 1.3 to 1.6 cm−1 (k = 2, coverage factor). It was also confirmed that the wavenumbers at 10°C and 35°C were within the expanded uncertainty; thus, these values should be widely useful for the calibration of Raman systems. [ABSTRACT FROM AUTHOR]

Raman shift is one of the most important parameters in Raman spectroscopy and is theoretically calculated from the difference in the wavenumbers of excitation and Raman scattering. At present, there are no standard procedures available to reliably estimate the Raman shift and evaluate its uncertainty from experimental results. In this study, we reliably estimated the Raman shift and evaluated its uncertainty for a non‐doped crystalline Si substrate (NMIJ CRM5606‐a) using a He‐Ne laser and its plasma lines (Ne emission lines). The Raman scattering wavenumber of NMIJ CRM 5606‐a was estimated by the bracket calibration method using the wavenumbers of the closest Ne emission lines. The Raman shift was determined from the differences in the theoretical wavenumbers of a He‐Ne laser and the observed Raman scattering. To evaluate the combined standard uncertainty, we considered the uncertainty originating from the He‐Ne laser and the Ne emission lines, the repeatability of experimental results, inhomogeneity of measuring points and spectral dispersion. The estimated Raman shift was 520.45 cm−1 ± 0.28 cm−1 (coverage factor k = 2). The Raman shift was validated by the other estimated Raman shifts obtained with other two Raman spectrometers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Eu3+-doped LnF 3 NPs prepared via a low-temperature thermal decomposition process. • Thermal stability, surface chemistry, and optical absorption studies. • Comparative Raman active modes were discussed. • The influence of host lattice on luminescence properties was investigated. The thermal co-precipitation approach was employed for the synthesis of the Eu3+-ion doped YF 3 , LaF 3, and GdF 3 nanoparticles (NPs) and compared their photophysical properties. Ammonium fluorite was used as a fluorine source for the synthesis of metal fluorides at lower temperatures. Luminescent lanthanide fluoride (LnF 3) NPs were characterized by different techniques containing X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), FT-Raman, UV/Visible absorption spectra, and photoluminescence spectroscopic procedures to investigate the crystal structural, thermal, Raman effect, surface, optical, and luminescent properties. XRD study shows two types of crystal phase orthorhombic in YF 3 :Eu & GdF 3 :Eu and hexagonal in LaF 3 :Eu NPs. TGA, FTIR, and absorption spectra studies show the exterior adsorbed –OH molecules, which assist in the development of colloidal solution in aqueous media. Raman vibrations were strongly affected which were correlated with the XRD reflection planes. In comparative photo-physical properties, the excitation and emission spectra exhibited remarkable intensities of the Eu3+-ion transitions. Similarly, the emission spectra of all three samples exhibited the highest emission efficiency of the magnetically-dipole(5D 0 →7F 2) transition in comparison to the electric-dipole 5D 0 →7F 1 transition, which reflected the transformation of the crystal symmetry. Comparative analysis was presented to investigate the role of the host lattice on crystallinity, thermal stability, and luminescent properties. These findings are highly fruitful in designing photonic-based applications including optical biosensors, fingermark detection, security systems, etc. [ABSTRACT FROM AUTHOR]

Raman imaging eliminates the need for staining procedures, providing label-free imaging to study biological samples. Recent developments in stimulated Raman scattering (SRS) have achieved fast acquisition speed and hyperspectral imaging. However, there has been a problem of lack of detectors suitable for MHz modulation rate parallel detection, detecting multiple small SRS signals while eliminating extremely strong offset due to direct laser light. In this paper, we present a complementary metal-oxide semiconductor (CMOS) image sensor using high-speed lock-in pixels for stimulated Raman scattering that is capable of obtaining the difference of Stokes-on and Stokes-off signal at modulation frequency of 20 MHz in the pixel before reading out. The generated small SRS signal is extracted and amplified in a pixel using a high-speed and large area lateral electric field charge modulator (LEFM) employing two-step ion implantation and an in-pixel pair of low-pass filter, a sample and hold circuit and a switched capacitor integrator using a fully differential amplifier. A prototype chip is fabricated using 0.11 μm CMOS image sensor technology process. SRS spectra and images of stearic acid and 3T3-L1 samples are successfully obtained. The outcomes suggest that hyperspectral and multi-focus SRS imaging at video rate is viable after slight modifications to the pixel architecture and the acquisition system. [ABSTRACT FROM AUTHOR]

The G peak position and structural changes of diamond-like carbon (DLC) are investigated as a function of temperature using Raman spectroscopy. Structural changes and surface oxidation are studied by comparing Raman spectra at room temperature with Raman spectra at high temperature. The use of Raman shift data of DLC for temperature calibration of the temperature profiles in heat-assisted magnetic recording using tip-enhanced Raman spectroscopy is discussed. [ABSTRACT FROM AUTHOR]

In this paper, Raman shifts of a-plane GaN layers grown on r-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition (LPMOCVD) are investigated. We compare the crystal qualities and study the relationships between Raman shift and temperature for conventional a-plane GaN epilayer and insertion AlN/AlGaN superlattice layers for a-plane GaN epilayer using temperature-dependent Raman scattering in a temperature range from 83 K to 503 K. The temperature-dependences of GaN phonon modes (A1 (TO), E2 (high), and E1 (TO)) and the linewidths of E2 (high) phonon peak are studied. The results indicate that there exist two mechanisms between phonon peaks in the whole temperature range, and the relationship can be fitted to the pseudo-Voigt function. From analytic results we find a critical temperature existing in the relationship, which can characterize the anharmonic effects of a-plane GaN in different temperature ranges. In the range of higher temperature, the relationship exhibits an approximately linear behavior, which is consistent with the analyzed results theoretically. [ABSTRACT FROM AUTHOR]