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Cu2ZnSn(S,Se)4 (CZT(S,Se)) thin films exhibit the characteristics necessary to be effective absorbers in solar cells. In this report, the room temperature experimental Raman scattering spectra, recorded at different excitation wavelengths, are systematically analyzed theoretically using the results of DFT harmonic frequencies calculations at the Γ-point for various modifications of kesterite (KS), stannite (ST), and pre-mixed Cu-Au (PMCA) crystal structures. The specific anharmonism‐induced features in the spectra of CZT(S,Se) crystals are identified, and the spectral lineshapes at varied strengths of anharmonic interaction are simulated. A robust agreement between the experimental Raman spectrum and the theoretical results is demonstrated, ensuring the reliability of estimating parameters related to anharmonic effects. Therefore, our findings show that incorporating anharmonism as an additional contribution to the phonon spectra, particularly in non-resonant cases, allows for a more accurate description of the vibrational properties of CZT(S,Se). This could play a crucial role in distinguishing between different phases of CZT(S,Se) materials and open new possibilities for the fabrication of solar cells with enhanced characteristics. [ABSTRACT FROM AUTHOR]

Magnetic fields have been used to deliver magnetic nanocomposites (MNCs) and alter mechanochemical transduction pathways in malignant tumors. We study mechanoluminescence (ML) of Walker-256 carcinosarcoma cells induced by the magneto-mechanochemical effects of Fe3O4–Au MNCs under a nonuniform rotating magnetic field (RMF). Photoluminescence (PL) and Raman spectra were recorded to investigate the optical response of MNCs. The PL spectrum of MNCs showed three broad emission bands with peaks at 525, 570 and 680 nm. MNCs underwent a phase transition attributed to localized surface plasmon resonance as indicated by the Raman spectra. ML intensity recorded from MNCs + cells + RMF was 3.5 and 1.4 times greater than chemiluminescence (CL) of MNCs + cells and cells alone, respectively (p ≤ 0.05). ML exhibited lesser variation than CL. The nonuniform distribution of a magnetic force exerted on MNCs resulted in more symmetric distributions of ML signals. Therefore, the observed ML emission could originate from the magneto-mechanochemically and light-induced free radical reactions in cancer cells in response to MNCs + RMF. The magneto-mechanochemical effects have the possibility to translate ML to cancer diagnosis and treatment by providing additional information about changes in breaking asymmetry to symmetric processes at the quantum level. [ABSTRACT FROM AUTHOR]

Purpose. is to analyze influence mechanisms of physicochemical coal properties on the degree of outburst risk as well as desorption kinetics of methane. Methods of scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and Raman scattering (RS) have been applied. The samples have been taken from Donbas coal seams varying in their ranks (i.e. carbonization degree). Findings. It has been identified that in the context of outburst hazardous zones, the ratio between integral intensity of spectral RS bands D and G, K = I(D)/I(G) shows abnormal dependence upon the nominal amount of volatile compounds connected with the impact by iron impurities. It has been defined that within the ferriferous coal samples, concentration of spins ns (i.e. the broken carbon bonds) correlates with iron content. Methane adsorption/desorption processes in the studied coal samples have been studied with the help of NMR method; in addition, they have been described using superposition of diffusion and filtration mechanisms. Originality. It has been understood that high iron content is typical for coal with a greater outburst hazardous degree. The abovementioned iron content and I(D)/I(G) and Ns correlation between the values determines the key role of iron impurities for coal metamorphism processes. For the first time, correlation between the outburst hazardous degree of coal seam and intensity of 3030 cm-1 IR band, stipulated by aromatic CH groups where hydrogen is in atomic status, has been identified. Practical implications. Predictability of outburst risk has been improved in the context of coal seam mining. [ABSTRACT FROM AUTHOR]

Theoretical and experimental vibrational spectra of ReSe2 nanocrystals, synthesized by self‐limited chemical vapor deposition (CVD), are reported. Scanning electron microscopy reveals that the nanocrystals have the shape of polygon nanoplates (NPs), 20 nm thick and about 100–300 nm wide. X‐ray diffraction studies determined their triclinic structure (space group, P‐1 [no. 2]). The wavenumbers of the Raman‐ and infrared (IR)‐active phonon modes were calculated using the density functional perturbation theory (DFPT), along with the dispersion curves and phonon density of states. The set of theoretical phonon wavenumbers is found to correlate well with the experimental Raman and IR spectra. We established that, unlike ReS2, ReSe2 does not exhibit a "phonon gap." Several "extra" bands in the experimental Raman spectrum of ReSe2 are argued to be defect‐induced contributions of phonons from F and Q critical points of the Brillouin zone. In addition, the effect of Fermi resonance is observed in the Raman spectrum of the ReSe2 NPs, which manifests itself in an increase of the intensity of second‐order bands due to their interaction with first‐order phonons. [ABSTRACT FROM AUTHOR]

The effects of built-in deformation and stress relaxation on the structural and optical properties for a 21-period AlN/GaN superlattice (SL) after implantation with argon ions have been studied. Upon implantation, the satellites' peaks in the X-ray diffraction spectra shift toward the smaller angles which indicate decreasing of tensile deformation in SL by the value of Δc/c = 0.28%. The SIMS analysis showed that the sputtering rate for the initial sample decreases with depth, which is explained by the effect of varying deformation fields in SL and a faster etching of SL layers with a larger deformation magnitude. The change in the sputtering rate of individual layers of SL after implantation also correlates well with the magnitude of deformation. Implantation of Ar+ ions into SL leads to relaxation of the system and more homogeneous distribution of bond energy in individual layers of superlattice. The Raman spectra of the implanted SL are characterized with a low-frequency shoulder in the most intense band of the GaN layer E2 (high), which testifies partial stress relaxation in SL. Thus, based on a comprehensive study of the initial and implanted SL, it has been concluded that point defects that occur during implantation activate the process of dislocations nucleation in the superlattice/GaN buffer layer interface, which reduces the compressive stresses in the GaN layers of SL. [ABSTRACT FROM AUTHOR]

Phonon spectra of two novel nonlinear optical crystals, PbGa2GeSe6 and PbGa2GeS6, are studied experimentally by Raman and infrared reflection spectroscopy and theoretically by density functional theory (DFT) lattice dynamics calculations. The experimental peak frequencies are compared with calculated vibration frequencies, and a very reasonable agreement is established. A comparative analysis of results for PbGa2GeSe6 and PbGa2GeS6 with earlier reported data on relevant binary and ternary metal chalcogenides clearly indicates that the similarity of their phonon spectra stems from the presence of GeS4 and GeSe4 tetrahedra as structural building blocks. [ABSTRACT FROM AUTHOR]