Fabrication, characterization and optical properties of Au-decorated Bi₂Se₃ nanoplatelets

Au-decorated Bi₂Se₃ nanoplatelet heterostructures are fabricated by a two-step process of thermal CVD at 600 °C and magnetron sputtering at room-temperature. The crystal structures and binding energies of rhombohedral Bi₂Se₃ and FCC Au are determined by XRD, HRTEM, XPS, and Raman spectroscopy. XPS and Raman spectroscopy reveal the interaction between Au and Bi₂Se₃ by shifting in the binding energies of Au-Au, Au-Se and Bi-Se bonds and the wavenumber of A_1g² and E_g² modes. Au-decorated Bi₂Se₃ nanoplatelet heterostructures are observed using FESEM, and confirmed by XPS, Raman spectroscopy, and HRTEM imaging. Their optical band gap of the Au-decorated Bi₂Se₃ nanoplatelet heterostructures increases with Au thickness about 1.92-fold as much as that of pristine Bi₂Se₃ (0.39 eV), owing to the Burstein-Moss effect. The optical absorptance of the Au-decorated Bi₂Se₃ nanoplatelet heterostructures revealed increment with wavelength from 200 to 500 nm and decrement with increasing wavelength from 500 to 800 nm.