Double-Crucible Vertical Bridgman Technique for Stoichiometry-Controlled Chalcogenide Crystal Growth

Precise stoichiometry control in single-crystal growth is crucial for both technological applications and fundamental research. However, conventional techniques such as flux and Bridgman methods often struggle with issues like nonstoichiometry and compositional gradients, challenges that are especially pronounced in systems with noncongruent melting behavior. Even in congruent melting systems like topological insulator Bi2Se3, slight deviations from the stoichiometric ratio can lead to substantial degradation of material properties, such as increased bulk conductivity that hinders the technological exploitation of its topological surface states. In this study, we present the double-crucible vertical Bridgman (DCVB) method, a novel approach that, for the first time, enables traveling solvent growth within a Bridgman furnace. This technique achieves enhanced stoichiometric control through continuous feeding of source material, liquid encapsulation, and high-pressure conditions. Using Bi2Se3 as a model system, we show that crystals grown via DCVB exhibit markedly improved stoichiometric precision and carrier concentrations reduced by one to two orders of magnitude compared to those grown by conventional Bridgman methods. The DCVB method thus offers a promising strategy for synthesizing large-scale, high-purity crystals, particularly for metal chalcogenides and pnictides that are difficult to grow due to noncongruent melting behavior.