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Hexagonal boron nitride (h-BN) is an important member of two-dimensional (2D) materials with a large direct bandgap, and has attracted growing interest in ultraviolet optoelectronics and nanoelectronics. Compared with graphene and graphite, h-BN has weak Raman effect because of the far off-resonance excitation, hence it is difficult to exploit Raman spectroscopy to characterize important properties of 2D h-BN, such as thickness, doping and strain effects. Here, we applied stimulated Raman scattering (SRS) to enhance the sensitivity of E2g Raman mode of h-BN. We showed that SRS microscopy achieves rapid high resolution imaging of h-BN with a pixel dwell time four orders of magnitude smaller than conventional spontaneous Raman microscopy. Moreover, the near perfect linear dependence of signal intensity on h-BN thickness and isotropic polarization dependence allow convenient determination of flake thickness with SRS imaging. Our results indicated that SRS microscopy provides a promising tool for high-speed quantification of h-BN and holds potential for vibrational imaging of 2D materials.
PMID: 31725258 [PubMed - as supplied by publisher]