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黑磷由于具有独特的各向异性而受到广泛的关注. 声子色散和电子能带结构的研究对于理解黑磷的性质及其在下一代各向异性纳米光电子器件中的应用有促进作用. 拉曼光谱作为材料的指纹谱, 可提供材料声子色散以及电子能带结构等信息. 根据拉曼选择定则, 多声子(两个或两个以上的声子)拉曼散射光谱可以探测整个布里渊区内的声子态密度. 然而, 一般来说, 相比于一阶拉曼散射, 高阶拉曼散射具有极低的强度. 为了克服这种限制, 本文通过多个激光波长来激发黑磷的拉曼光谱, 观测到了丰富的二阶和三阶拉曼模. 同时, 采用特定的偏振配置避免了黑磷光学各向异性所导致的双折射效应对拉曼强度的影响, 结合声子色散及其对称性对680—930 cm–1范围内的多声子拉曼峰进行了指认, 这表明非布里渊区中心的声子对黑磷的二阶和三阶拉曼散射有重要贡献. 本文所提出的研究高阶拉曼散射的方法对研究其他各向异性材料中的共振拉曼光谱具有借鉴作用.Black phosphorus (BP) has been attracting intense interest due to its unique anisotropic properties. The investigations on phonon dispersion and electronic band structure could expand the understanding of the properties of BP and promote its application on next generation nano-electronic devices. As the fingerprint of materials, Raman spectroscopy can provide the information of their phonon dispersion and electronic band structure. According to the Raman selection rule, Raman process involving multiple (two or more) phonons can be used to probe the phonon density of states within the whole Brillouin zone. However, the intensity of high-order Raman modes is much lower than that of the first-order Raman mode. To break through the limit of low intensity, here, we measured the resonant Raman spectroscopy of BP excited by several wavelength lasers and observed rich information about high-order Raman modes in the spectral range of 680–930 cm–1. To further investigate high-order Raman modes and avoid the birefringence effects from optical anisotropy on Raman intensity, we employ a special polarization configuration to obtain resonant Raman spectra and Raman intensity as a function of excitation wavelength. All the observed high-order Raman modes are certainly assigned, according to the phonon dispersion and symmetry analysis of related phonons. This indicates the great contribution of phonons within the Brillouin zone to the second- and third-order Raman scattering. This work proposes a general and systematical method to investigate high-order Raman modes, and paves ways for the researches of phonon dispersion and resonance Raman spectroscopy in other anisotropic materials.
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Keywords:
- black phosphorus /
- second-order Raman mode /
- third-order Raman mode /
- resonant Raman scattering /
- optical anisotropy








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