Angle-Resolved Intensity of In-Axis/Off-Axis Polarized Micro-Raman Spectroscopy for Monocrystalline Silicon

Monocrystalline silicon (c-Si) is still an important material related to microelectronics/optoelectronics. The nondestructive measurement of the c-Si material and its microstructure is commonly required in scientific research and industrial applications, for which Raman spectroscopy is an indispensable method. However, Raman measurements based on the specific fixed Raman geometry/polarization configuration are limited for the quantified analysis of c-Si performance, which makes it difficult to meet the high-end requirements of advanced silicon-based microelectronics and optoelectronics. Angle-resolved Raman measurements have become a new trend of experimental analysis in the field of materials, physics, mechanics, and optics. In this paper, the characteristics of the angle-resolved polarized Raman scattering of c-Si under the in-axis and off-axis configurations are systematically analyzed. A general theoretical model of the angle-resolved Raman intensity is established, which includes several alterable angle parameters, including the inclination angle, rotation angle of the sample, and polarization directions of the incident laser and scattered light. The diversification of the Raman intensity is given at different angles for various geometries and polarization configurations. The theoretical model is verified and calibrated by typical experiments. In addition, this work provides a reliable basis for the analysis of complex polarized Raman experiments on silicon-based structures.

Zeptomolar detection of 4-aminothiophenol by SERS using silver nanodendrites decorated with gold nanoparticles

In the present work we report a simple, fast, reproducible and cheap methodology for SERS substrate fabrication of silver dendritic nanostructures (prepared by electrodeposition) decorated with gold nanospheres by electrophoretic deposition. This is the first report where a metal dendritic nanostructure has been decorated with another type of metal nanoparticles by this technique. The decorated nanostructures were used directly as SERS substrate using 4-aminothiophenol (4-ATP) as analyte. The objective of the decoration is to create more hot-spots in order to detect the analyte in a lower concentration. Decorated nanodendrites had a detection limit one million times lower than bare silver nanodendrites and all the substrates showed an increase in the Raman intensity at concentrations below 1 nM; because this concentration corresponds to the threshold for the formation of a monolayer resulting in a triple mechanism of intensity increase, namely electric field, chemical factor and hot-spots. 4-ATP was detected in zeptomolar concentration, which is below 1 ppq, corresponding to an analytical enhancement factor (AEF) in the order of 1015.

Enhanced Raman Spectra in Femtosecond Laser Inscribed Yb:YVO4 Channel Waveguides

The femtosecond laser writing with double-line technique was employed to fabricate buried channel waveguides with different widths in Yb:YVO4 crystal. Model profiles of the waveguides were captured using the endface coupling setup at the wavelength of 633 nm under TE and TM polarization. Furthermore, the confocal micro-Raman spectra in bulk and waveguide areas were studied at the wavelength of 633 nm. The enhanced Raman intensity were performed in waveguide areas.

Operando Raman Shift Replaces Current in Electrochemical Analysis of Li-ion Batteries: A Comparative Study

Li-rich and catalytically active γ-LixV2O5 (x = 1.48) was investigated as a cathode for its heterogeneous charge transfer kinetics. Using a specially designed two-electrode system lithium half cell, Butler–Volmer analysis was performed, and Raman spectra were acquired in 18 mV intervals. A direct correlation was observed between the Raman shift of the active modes Ag,Bg, Au, and Bu, and the development of the Faraday current at the working electrode. The Raman intensity and the Raman shift were implemented to replace the current in a Tafel plot used for the analysis of Butler–Volmer kinetics. Striking similarities in the charge transfer proportionality constants α were found for current and Raman-based analysis. The potential of this new method of Raman-aided electrochemical detection at the diffraction limit is discussed.

A Novel Polyaniline Nanofiber Combined with Toluidine Blue as a Sensitive Detection Platform for Lignin by Raman Spectroscopy

Raman spectroscopy is widely applied in wood science because of its features of being nondestructive, rapidity, and high resolution. However, Raman scattering is weak, and the Raman signal is easily disturbed by autofluorescence arising from endogenous fluorescent molecules in biological tissue. In this work, a sensitive lignin detection platform was fabricated by a composite with a polyaniline (PANI) nanofiber and toluidine blue (TB) under the excitation of visible light. In this platform, TB acts as a specific marker for lignin, and a PANI nanofiber was used as a reinforcing reagent to improve the Raman intensity of TB. When wood slice is impregnated with TB/PANI, the lignin in wood can be precisely labeled with the TB, and the Raman intensity of TB had a threefold increase at 532 nm excitation. This TB/PANI detection platform is expected to make a significant contribution in qualitative and quantitative analysis of lignin to avoid autofluorescence in various lignin-based biosciences.

Detection and quantitation of cellulose II by Raman spectroscopy

In cellulose materials, the cellulose II polymorph is often present either exclusively or inconjunction with cellulose I, the natural cellulose. Moreover, in regenerated andmercerized fibers (e,g., viscose and lyocell), natural cellulose adopts to the crystalstructure cellulose II Therefore, its detection and quantitation are important for acomplete assessment of such materials investigations. In the Raman spectra of suchmaterials, a band at 577 cm -1 is typically observed indicating the presence of thispolymorph. In the present study, to quantify the content of cellulose II, a calibrationmethod was developed based on the intensity of the 577 cm -1 peak relative to the1096 cm -1 band of cellulose. For this purpose, in addition to pure cellulose I andcellulose II samples (respectively, Avicel PH-101 and mercerized Avicel PH-101; hencereferred to as Avicel I and Avicel II), a set of five samples were produced by mixingthem in known quantities of Avicel I and Avicel II. The crystalline cellulose II contents ofthe samples were calculated based on the X-ray crystallinity of mercerized Avicel I.These seven samples were included in the calibration set and their Raman spectrawere obtained. Subsequently, Raman intensity ratios I 577 /I 1096 were calculatedby taking ratios of peak intensities at 577 and 1096 cm -1 . These ratios were plottedagainst the % of crystalline cellulose II present in the calibration set samples and thetwo were found to be linearly correlated (R 2 = 0.9944). The set-samples were alsoanalyzed using XRD which were then compared with the Raman method developedhere. Compared to XRD, the Raman method was found to be more sensitive atdetecting and quantifying cellulose II. Additionally, several cellulose II containingmaterials were analyzed by the new Raman method.

Angle-Resolved Intensity of Polarized Micro-Raman Spectroscopy for 4H-SiC

Raman spectroscopy is an indispensable method for the nondestructive testing of semiconductor materials and their microstructures. This paper presents a study on the angle-resolved intensity of polarized micro-Raman spectroscopy for a 4H silicon carbide (4H-SiC) wafer. A generalized theoretical model of polarized Raman intensity was established by considering the birefringence effect. The distributions of angle-resolved Raman intensities were achieved under normal and oblique backscattering configurations. Experiments were performed on a self-built angle-resolved Raman system, which verified the validity of the proposed model and achieved the identification of crystal orientations of the 4H-SiC sample.

The potential of raman spectroscopy as a monitoring tool for thermal therapy

Laser Interstitial thermal Therapy (LITT) is a minimally invasive technique for treating localized solid tumors through heating with light. LITT is not routinely employed in a clincal setting due to difficulties in real-time monitoring of tissue heating. This work investigates the feasibility of Raman Spectroscopy (RS) to monitor thermal therapies. RS has the ability to detect changes in the seconcary structure of proteins, and may prove useful as an indicator of tissue coagulation in real-time during thermal therapy. Tissue equivalent albumen phantoms were heated in a water bath and bovine muscle samples where heated in a water bath and through laser photocoagulation. Raman spectra were acquired after heating and increases in the overall Raman intensity and shifts in major band locations were observed after heating. Correlations between Raman intensity and thermal dose were also observed. These results indicate that RS may be employable as a real-time monitoring tool for LITT.

The potential of raman spectroscopy as a monitoring tool for thermal therapy

Laser Interstitial thermal Therapy (LITT) is a minimally invasive technique for treating localized solid tumors through heating with light. LITT is not routinely employed in a clincal setting due to difficulties in real-time monitoring of tissue heating. This work investigates the feasibility of Raman Spectroscopy (RS) to monitor thermal therapies. RS has the ability to detect changes in the seconcary structure of proteins, and may prove useful as an indicator of tissue coagulation in real-time during thermal therapy. Tissue equivalent albumen phantoms were heated in a water bath and bovine muscle samples where heated in a water bath and through laser photocoagulation. Raman spectra were acquired after heating and increases in the overall Raman intensity and shifts in major band locations were observed after heating. Correlations between Raman intensity and thermal dose were also observed. These results indicate that RS may be employable as a real-time monitoring tool for LITT.