SEMIMETAL TO SEMICONDUCTOR TRANSITION IN CARBON NANOPARTICLES

Electron energy loss spectroscopy (EELS) has been used to observe size dependent changes in the electronic states of isolated, nanocrystalli ne carbon particles supported on SiO2 substrates. The structure and si ze distribution of the particles have been characterized by Raman scat tering, Anger electron spectroscopy, and electron microscopy. EELS obs ervations indicate that a semimetal to semiconductor transition occurs for particles smaller than 1 nm. In addition, hydrogen adsorption is found to significantly alter the electronic states, demonstrating that both finite size and dangling bond effects modify the properties of s mall carbon nanocrystallites.