Effects of inter-nanocrystal distance on the photoluminescence and electrical properties of silicon nanocrystals

Abstract

The effect of the variation of the distance between size-controlled silicon nanocrystals (Si NCs) on their electrical properties and low-temperature photoluminescence (PL) emission are studied in the present project. Via the superlattice approach, SiO2 barrier thicknesses from 1 nm to 3 nm, with 0.5 nm steps, alternated with layers of silicon-rich oxynitride (SRON), were deposited on a p-type Si substrate through plasma-enhanced chemical-vapor deposition. After an adequate annealing process, the precipitation of Si NCs was achieved. The low-temperature PL data were depositted using a physical model which takes into account the electron-phonon interaction between NCs, from which the average phonon energy was estimated. The obtained results demonstrate that thicker barriers (i.e., higher inter-NC distance) present lower average phonon energy, which is ascribed to a weaker NC-NC interaction and a greater carrier confinement. In addition, the I(V ) from NCs-containing device were studied. High applied electric fields resulted in Fowler-Nordheim (F-N) mechanism dominating charge transport, from which the values of the band offset energy between the electrode and the NCs-containing dielectric were figured out, being this value larger for thicker barriers, in agreement with a lower injection efficiency.