Temperature dependence of Raman shift in defective single-walled carbon nanotubes

Raman scatterings of both pristine and defective single-walled carbon nanotubes were measured. Defects on carbon nanotubes (CNTs) were induced by UV/O3 treatment, and the correlation between the temperature dependence of the Raman shift of the G-band and the crystallinity of CNTs was investigated. In the temperature range of 250–600 K, a gradual negative change in the slope was observed; the linear shift of the Raman G-band frequency with respect to temperature increased as the crystallinity deteriorated. This phenomenon is attributed to the increase in the fourth-order phonon-phonon scattering interaction resulting from the induced defects.

Effect of Nonlinear Dispersion Fiber Length and Input Power on Raman Scattering

The increasing demand for information transmission makes the problem of establishing a laser system is operating in C-band (1530-1565nm) wavelength region is a significant task, which attracts a lot of researchers' attention lately. In this paper, the ability to produce signals of multi wavelengths using a single light source was adopted to employ the Raman scattering effect for establishing Raman shift configuration-based multi-wavelength fiber lasers, which is not currently addressed in available schemes. This is what prompted to simulate the performance of C-band multi-wavelength produced by Raman fiber laser that utilizing fiber Bragg grating (FBG) to amplify pumped power and also utilizing the single-mode fiber (SMF) as the nonlinear gain medium. The proposed laser system is designed by OptiSystem software. The resulted maximum output power was 22.07dB at Wavelength Division Multiplexing (WDM) of 23.01dB input power. The achieved multi-wavelength that generated by Bragg grating and SMF was containing six Stokes and anti-Stokes, they are: 1548.51nm, 1549, 31nm, 1550.116nm, 1550.91nm, 1551.72nm, and 1552.52nm, in which the resulted computed efficiency of the system was raised up to 80.23% at input power 20 dB and dispersion fiber length of 0.2 km.

Anharmonic Effects in Ordered Kesterite-Type Cu2ZnSnS4

We performed an in-depth investigation and analysis of the effect of temperature on the Raman-active A-modes of bulk kesterite-type Cu2ZnSnS4 within the 300–460 K temperature range. We acquired the individual contributions to each Raman mode, namely, the thermal expansion and anharmonic interactions terms responsible for the Raman shift and broadening with temperature. Our results indicate that the Raman shift with temperature is dominated by the thermal expansion term, whereas the broadening is mainly governed by three-phonon damping processes in this material. Considering relevant results from the literature, it appears that dimensionality is a key factor in regulating the dominant phonon decay mechanism.

Rapid Detection and Quantification of Plant Innate Immunity Response Using Raman Spectroscopy

We have developed a rapid Raman spectroscopy-based method for the detection and quantification of early innate immunity responses in Arabidopsis and Choy Sum plants. Arabidopsis plants challenged with flg22 and elf18 elicitors could be differentiated from mock-treated plants by their Raman spectral fingerprints. From the difference Raman spectrum and the value of p at each Raman shift, we derived the Elicitor Response Index (ERI) as a quantitative measure of the response whereby a higher ERI value indicates a more significant elicitor-induced immune response. Among various Raman spectral bands contributing toward the ERI value, the most significant changes were observed in those associated with carotenoids and proteins. To validate these results, we investigated several characterized Arabidopsis pattern-triggered immunity (PTI) mutants. Compared to wild type (WT), positive regulatory mutants had ERI values close to zero, whereas negative regulatory mutants at early time points had higher ERI values. Similar to elicitor treatments, we derived an analogous Infection Response Index (IRI) as a quantitative measure to detect the early PTI response in Arabidopsis and Choy Sum plants infected with bacterial pathogens. The Raman spectral bands contributing toward a high IRI value were largely identical to the ERI Raman spectral bands. Raman spectroscopy is a convenient tool for rapid screening for Arabidopsis PTI mutants and may be suitable for the noninvasive and early diagnosis of pathogen-infected crop plants.

L attice V ibrational C haracteristics , Crystal Structure s , and D ielectric P roperties of Li Mn PO 4 Microwave Dielectric Ceramics as a Function of Sintering Temperature

LiMnPO4 (LMP) microwave dielectric ceramics were manufactured at different temperatures via a standard solid-state reaction method, and the LMP ceramic sintered at 750 °C displayed dielectric properties of εr = 7.82, Q × f = 29,189 (f = 12.7 GHz). The lattice vibrational characteristics of LMP ceramics were studied utilizing both infrared reflection and Raman scattering spectroscopy to clarify the basic principle of the dielectric response. The intrinsic properties that were fitted and simulated based on the infrared spectra agreed with the measured property values. The low-frequency vibrational modes contributed more to the dielectric properties than the high-frequency modes. Upon increasing the temperature, the permittivity was positively correlated with the bond length but showed the opposite trend of the Raman shift of mode 9 Ag(υ1). The Q × f value was positively correlated with the packing fraction but negatively correlated with the FWHM of mode 10 Ag(υ3). Thus, the structure-property relationships of LMP ceramics were established as a function of sintering temperature.

Effect of Substrate Biasing on the Epitaxial Growth and Structural Properties of RF Magnetron Sputtered Germanium Buffer Layer on Silicon

High-quality single-crystal-like Ge (004) thin films have been epitaxially grown using radio-frequency magnetron sputtering on Si (001) substrates successfully. The crystalline quality of the Ge films can be obviously improved by applying a positive bias on the substrate holder. X-ray diffraction measurements show that the single-crystal-like Ge film has a narrow full width at half maximum of 0.26°. The perpendicular lattice constant (aGe⊥) and in-plane lattice constant (aGe∥) are 0.5671 and 0.564 nm. The Raman shift full width at half maximum shows that the defects in the film are obviously reduced. Transmission electron microscopy diffraction patterns also show that the Ge (004) film has good crystalline quality. The results can be applied as Ge buffer layers on Si substrates for the fabrication of high-efficiency III–V solar cells and photodetectors.