Evidence for changes in the electronic and photoluminescence properties ofsurface-oxidized silicon nanocrystals induced by shrinking the size of thesilicon core

Web-like aggregates of Si nanocrystals produced by laser vaporization-contr olled condensation technique are allowed to oxidize slowly in air and the p hotoluminescence (PL) is measured. A significant shift in the PL red band f rom 1.83 to 1.94 eV is observed. The bonding structure is established by co rrelating the PL data with the photon-yield electronic structure measuremen t's using soft-X-ray fluorescence (SXF) and photon-yield near-edge X-ray ab sorption fine structure (NEXAFS) techniques. The results indicate that as t he nanoparticles oxidize, the radius of the crystalline core decreases, whi ch gives rise to a larger bandgap and consequently to the observed blue shi ft in the PL band. (C) 2000 Elsevier Science B.V. All rights reserved.