Figure 1. Synthesis and characterizations of the hexagonal single-crystalline Bi₂Te₃ NPs exposed with {0001} facets.

(a, b) Scanning electron microscopy images of the as-grown NPs. The inset in (b) is a representative individual NP. (c) TEM image of the as-grown NPs. (d) TEM image of a defective Bi₂Te₃ NP (top) and its element maps (bottom). (e) HRTEM image of the Bi₂Te₃ NP in (d) taken along the [0001] direction, revealing a high quality crystalline structure. The inset is the corresponding fast Fourier transform (FFT) image. (f) Side (left) and top (right) views of the crystal structure of Bi₂Te₃. A quintuple layer (Te1-Bi-Te2-Bi-Te1) is indicated by a double-headed arrow. (g) Selected area diffraction pattern taken along the [0001] direction.