Binary Semiconductor Nanoclusters: from Magic Sizes to Atomic Precision

Chenjie Zeng

University of Florida

Semiconductor nanocrystals, also known as quantum dots, are important building blocks for energy and information technologies including transistors, solar cells, and light-emitting diodes. Nanoclusters are ultrasmall nanocrystals with sizes of ~1 nm to ~3 nm and containing tens to hundreds of core atoms. During the synthesis of semiconductor nanoclusters (including II-VI and IV-VI ones), magic-sized clusters (MSCs) are frequently observed, as characterized by (i) their consistent excitonic absorption peaks and (ii) discontinuous redshift of peaks during their growth. These features indicate MSCs have atomically defined core structures and their sizes increase in a quantized manner. However, the exact sizes, cores, and surface structures of MSCs remain largely “magic” and elusive. In contrast, atomically precise clusters have precise-defined structures not only in the core but also on the surface, therefore they can be assembled into single crystals and the total structures of clusters can be unambiguously determined by X-ray crystallography. In this presentation, we will discuss recent progress from our group to control atomic precision in syntheses and structures of semiconductor MSCs, including their nucleation, growth, surface coordination, and transformation. The obtained clusters provide important insights into the hierarchical structures of semiconductor clusters at the atomic core, coordination interface, organic surface, and inter-cluster levels and shield light on the chirality, polarity, and photoluminescent properties of semiconductor clusters.