Crystal defect control of topological insulator Bi₂Se₃ using a new modified Bridgman crystal growth method

Bridgman growth, which is a prevalent method for melt-based single crystal growth, often has limited control on crystal defects. For instance, topological insulator Bi₂Se₃ grown using conventional Bridgman method is often heavily doped due to the high-density crystal defects caused by nonstoichiometric composition. In this talk, we will introduce a new modified Bridgman method, i.e. double crucible vertical Bridgman (DCVB), which has potential to grow crystals with precisely controlled chemical composition. This method uses a double-crucible geometry with the upper crucible continuously feeding source material to the bottom growth crucible. Moreover, this system also allows for applying high pressure (up to 10 atm) and implementing chemical encapsulation. The combination of these advantages enables the control of composition of the melt in the growth crucible, thus improving the quality of grown crystals. We took Bi₂Se₃ as an example to demonstrate DCVB growth. Our preliminary test growths have shown that the carrier density of DCVB-grown Bi₂Se₃ single crystal is as low as ~ 8.5*10¹⁷, which is already one or two orders of magnitude smaller than those crystals grown using conventional melt/Bridgman growth methods, indicating that DCVB growth can lower crystal defect density.