Quantum effects in anisotropic semiconductor clusters: Colloidal suspensions of Bi sub 2 S sub 3 and Sb sub 2 S sub 3.

Transmission electron microscopy (TEM), optical absorption, dynamic light scattering and scanning tunneling microscopy (STM) have been used to characterize colloidal clusters of Bi sub 2 S sub 3 and Sb sub 2 S sub 3. These layered semiconductor clusters were found by TEM to grow to sizes ranging from 16- 90angstroms. Consistent with quantum confinement of charge carriers in small microcrystalline volumes, the optical absorption spectra were blue-shifted ~ 0.7eV from the bulk band gaps of the materials. These small clusters escaped detection by in situ dynamic light scattering and only particles roughly five times larger could be readily detected.