Surface-Facet-Dependent Phonon Deformation Potential in Individual Strained Topological Insulator Bi2Se3 Nanoribbons

摘要

Strain is an important method to tune the properties of topological insulators. For example, compressive strain can induce superconductivity in Bi2Se3 bulk material. Topological insulator nanostructures are the superior candidates to utilize the unique surface states due to the large surface to volume ratio. Therefore, it is highly desirable to monitor the local strain effects in individual topological insulator nanostructures. Here, we report the systematical micro-Raman spectra of single strained Bi2Se3 nanoribbons with different thicknesses and different surface facets, where four optical modes are resolved in both Stokes and anti-Stokes Raman spectral lines. A striking anisotropy of the strain dependence is observed in the phonon frequency of stained Bi2Se3 nano ibbons grown along the < 11 (2) over bar0 > direction. The frequencies of the in-plane E-g(2) and out-of-plane A(19)(1) modes exhibit a nearly linear blue-shift against bending strain when the nanoribbon is bent along the < 11 (2) over bar0 > direction with the curved {0001} surface. In this case, the phonon deformation potential of the E-g(2) phonon for 100 nm-thick Bi2Se3 nanoribbon is up to 0.94 cm(-1)/%, which is twice of that in Bi2Se3 bulk material (0.52 cm(-1)/%). Our results may be valuable for the strain modulation of individual topological insulator nanostructures.