BiSb quantum dots synthesized by pulsed laser ablation in acetone: structural and optical characterization

Bismuth antimonide (BiSb), a narrow-bandgap semiconductor, has attracted considerable interest for quantum applications due to its remarkable band structure and unique electronic properties. Composed of group V semimetals Bismuth (Bi) and Antimony (Sb), this miscible binary alloy forms a fully solid solution throughout the entire composition range. This material exhibits insulating behavior in its bulk and displays conducting surface states, making it the first experimentally observed 3D topological insulator. The alloy’s composition plays a crucial role in shaping its electronic band structure. Indeed, Bi_1-xSb_x undergoes a series of changes in its electronic structure as the Sb concentration increases: transitioning from a semimetal to an indirect bandgap semiconductor, followed by a direct bandgap semiconductor, then back to an indirect bandgap, and finally to a semimetal.

A BiSb target in pellet form (99.99% purity, from Sigma-Aldrich), cleaned with acetone, was placed at the bottom of a 50 mL single-neck round-bottom flask and submerged in 10 mL of acetone. Bottom ablation was carried out using a Q-switched Nd: YAG laser from Electro Scientific Industries operating at 1064 nm with a repetition rate of 1 kHz for 5 minutes. Morphological and structural properties were analyzed using HRTEM, EDX, Raman, XRD, UV-Vis, zeta potential, and DLS.

The size of the QDs was centered around 9 ± 2 nm and was spherical in shape. The bandgap was measured to be around 2.02 ± 0.27 eV, which is significantly higher than the bulk value. Strong evidence of quantum confinement was observed, as indicated by the peak shift in the Raman spectrum.

BiSb quantum dots were successfully synthesized for the first time using the PLAL technique. The QDs exhibited a spherical shape with a size of around 9 ± 2 nm and a significantly increased bandgap of approximately 2.02 eV, indicating strong quantum confinement effects. These results highlight the potential of BiSb QDs for quantum and optoelectronics applications.