Water-Assisted Growth of Bi₂Te₃-Sb₂Te₃ Lateral Heterostructures for Enhanced Second Harmonic Generation

The heterostructures incorporated with two or more distinctive two-dimensional (2D) materials have attracted great attention because they could give rise to enhanced property in comparison with their individual counterparts. Here, a water-assisted two-step rapid physical vapor deposition (rPVD) method was explored and used to synthesize Bi₂Te₃-Sb₂Te₃ lateral heterostructures (LHS) successfully. The Bi₂Te₃-Sb₂Te₃ LHS is in nearly uniform size, and grows along three particular orientations with the intersection angles of 120°. Interestingly, we found that the water molecules play a significant role in determining the growth orientation, namely whether it will grow along the vertical or lateral direction in 2D structure. Hence, a growth mechanism of LHS based on the water-assisted two-step rPVD was present, which can be used as a general strategy and extended to the growth of other 2D heterostructures or homostructures, such as SnS-SnSe LHS and SnS-SnS lateral homostructures. Furthermore, the second-harmonic generation intensity of the Bi₂Te₃-Sb₂Te₃ LHS is much stronger than that of the Bi₂Te₃/Sb₂Te₃ vertical heterostructures (VHS). This work opens a new approach for the synthesis of water-assisted lateral 2D heterostructures or homostructures and offers a new method to enhance the second-harmonic generation properties of topological insulating materials.