The treatment of the hyper-Raman scattering by 2LO phonons in semiconductors with equal effective masses of electrons and holes

Semenova, L. E.; Nikolaeva, G. Yu.; Пашинин, П. П.; Prokhorov, K. A.

doi:10.1134/s1054660x09040355

Cited by 2 publications

(2 citation statements)

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“…SORRS is not bound by the same phonon selection rules as first-order resonant Raman (FORS) or spontaneous Raman scattering (SRS) and can produce phonons with multiple wavevectors. 35 It is probable that boron carbide phonons identified in Figure 8, generally silent under SRS, become enhanced under conditions of electronic resonance. To achieve the required resonance, the laser energy must be equivalent to a strong electronic absorption band.…”

Section: Resultsmentioning

confidence: 99%

“…Second‐order Raman effects have been shown to enhance specific vibrational modes through electronic resonant enhancements in semiconductors; 34–37 however, very few researchers have considered the possibility of second‐order Raman scattering (SORRS) in the boron carbides. SORRS is not bound by the same phonon selection rules as first‐order resonant Raman (FORS) or spontaneous Raman scattering (SRS) and can produce phonons with multiple wavevectors 35 . It is probable that boron carbide phonons identified in Figure 8, generally silent under SRS, become enhanced under conditions of electronic resonance.…”

Section: Resultsmentioning

confidence: 99%

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Optical characterization of boron carbide powders synthesized with varying B‐to‐C ratios

2022

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Boron carbide powders were synthesized from elemental powders and studied using X-ray diffraction (XRD) and UV-visible diffuse reflectance, Raman, and diffuse reflectance IR spectroscopies. Following reaction at 1400 • C for 6 h, synthesized powders exhibited possible faulting as suggested by XRD patterns. B 3 C, B 4.3 C, and B 5 C powders contained graphitic carbon whereas the boron carbides with higher B/C ratios contained no residual carbon, suggesting that the carbon rich phase boundary is likely temperature dependent. Analysis by Raman and IR spectroscopy suggested that Raman spectra are influenced by excitation frequency due to resonance. We suggest that measurement of boron carbides with resonant Raman lifts the selection rules to allow measurement of Raman silent modes that are present in the IR spectra. Optical reflectance of the boron carbide powders revealed that the B/C ratio governed the indirect and direct optical band gaps of the faulted powders. B 3 C and B 4.3 C powders were light gray in spite of the presence of the carbon, whereas B 5 C, B 6.5 C, B 10 C, and B 12 C were gray, green, brown, and dark brown, respectively. Increasing carbon content increased the optical indirect band gap from 1.3 eV for B 12 C to 3.2 eV for B 3 C, causing the observed color changes.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%