Piezoelectric substrate-induced strain engineering on tuning polarized Raman spectra of crystalline black phosphorus

A black phosphorus (BP) ultrathin nanosheet has significant research values in broad fields ranging from nano-electronics/photonics to quantum physics. Here, a piezoelectric actuator is utilized to perform biaxial strain engineering for the investigation of anisotropic Raman response of the ultrathin BP transferred to the oxide dielectric substrate. Three characteristic peaks exhibit redshift when tensile strain is applied, while the peaks reveal blueshift under compressive strain. When applying compressive strain of -0.2%, the Raman shift rate of B2g mode can reach up to 15.3 cm-1/%. In contrast, with the application of 0.2% tensile strain, the B2g mode is shifted by -12.2 cm-1/%. Furthermore, we calculated the Grüneisen parameters to deduce the relationship between the tensile or compressive strain and phonon behavior of crystalline BP. The physical mechanism behind the observation of strained Raman response is discussed, which is related to the variations of bond angle and bond length in BP. Additionally, biaxial strain modulation may change the anisotropic dispersion of BP, revealing the significant potential of BP in innovative polarized light detection.