Transmission electron microscopy (TEM), optical absorption, dynamic light scattering, and scanning tunneling microscopy (STM) have been used to characterize colloidal clusters of Bi2S3 and Sb2S3. These layered semiconductor clusters were found by TEM to grow to sizes ranging from 16 to 90 Å. Consistent with quantum confinement of charge earners in small microcrystalline volumes, the optical absorption spectra were blue-shifted ≈0.7 eV from the bulk band gaps of the materials. These small clusters escaped detection by in situ dynamic light scattering, and only particles roughly 5 times larger could be readily detected. Preliminary results with a scanning tunneling microscope seem to support the amsotropic disklike geometry of the clusters, and for Bi2S3 we estimate cluster thicknesses of 20-30 Å. With the TEM and STM measurements of the cluster geometry and a simple particle-in-a-box model, we calculate band edge shifts which are in reasonable accord with the optical experiments.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry