Microcrystallites of the layered semiconductor ${\mathrm{PbI}}_2$ were prepared in colloidal form and examined by transmission electron microscopy and optical absorption. The crystallites have lateral dimensions grouped around 12, 18, and 29 Å corresponding to close-packed clusters with bulk ${\mathrm{PbI}}_2$ symmetry. Blue-shifted absorption features can be explained by carrier confinement in these differently sized crystallites, each a single layer (∼7 Å) thick.

• Received 27 January 1986

DOI:https://doi.org/10.1103/PhysRevB.33.5953