Interference‐enhanced deep‐ultraviolet Raman signals of hexagonal boron nitride flake and its underlying silicon substrate

We take hexagonal boron nitride (hBN) flakes exfoliated on SiO 2/Si substrates as a prototype, to demonstrate how to enhance the Raman signals both from ultra‐thin layered materials and the underlying opaque substrate excited by deep ultraviolet (DUV) laser. We found that the interference effect in the hBN/SiO 2/Si multilayered structure can largely enhance Raman intensity of hBN flake and the underlying Si substrate under 266‐nm excitation. This enhancement effect is more significant than that under visible excitation. With increasing the thickness of SiO 2 layer in the substrate, the corresponding hBN and Si Raman intensity can vary by up to ∼ 4 and ∼2 orders of magnitude under 266‐nm excitation, respectively. This method can be applicable to enhance Raman signal from other two‐dimensional materials under DUV excitation by tuning the thickness of SiO 2 layer in the SiO 2/Si substrate. The enhancement of the DUV Raman signals of hBN flake and its underlying silicon substrate is achieved by the interference effect in the hBN/SiO2/Si multilayered structure, which is confirmed by the calculation based on transfer matrix formalism. By increasing the thickness of SiO2 layer in the underlying substrate of hBN flake, the DUV Raman intensities of hBN flake and Si can vary up to ~4 and ~2 orders of magnitude under 266‐nm excitation, respectively.