ELECTRONIC AND MECHANICAL-PROPERTIES OF NANOCRYSTALLINE COMPOSITES WHEN APPROACHING MOLECULAR-SIZE

Many physical, chemical and mechanical properties of solids change whe n the crystalline size decreases to 1-2 nm, which is the typical limit of the stability of the crystalline phase. We summarize the recent pr ogress in the research on the optoelectronic properties of semiconduct or nanocrystals (nc) with emphasis on nc-Si/a-SiO2 composites in which the surface of the silicon nanocrystals are passivated and the crysta llites are separated by the oxide. The second part of the paper deals with the mechanical properties of novel superhard nanocrystalline/amor phous composites which hardness approaches that of diamond. (C) 1997 E lsevier Science S.A.