Abstract

The first direct absorption spectra have been obtained for size-selected, gas-phase neutral semiconductor clusters. Containing only 5-70 atoms, these clusters are too small to have either the bulk band structure or bulk excitations. Just what these clusters look like and just when they cross over to bulk structures is intensely debated. Our spectra reveal surprises: minute semiconductor clusters have surprisingly similar spectra over a wide range of sizes. Furthermore, their optical signatures have much in common with those of the bulk semiconductor forms.

© 1993 Optical Society of America