Synthesis of silicon quantum dots in zinc silicate matrix by low-temperature process: Optical, structural and electrical characterization

Silicon nano-crystallites dispersed in an insulating matrix of zinc silicates have been obtained by a two-step process, consisting of sputtering deposition of several alternated amorphous silicon and zinc oxide thin layers, followed by a chemical reaction carried out under vacuum at comparatively low temperature (from 450 degrees C to 560 degrees C) between stratified reagents. This low cost, low temperature and scalable process has to be considered promising in quantum dot fabrication technology. Several characterization techniques have been employed and large evidence has been found for the presence of silicon and zinc oxide nano-crystallites showing quantum confinement effect and related band gap enlargement. Photoluminescence phenomenon has been observed in the range 550-850 nm and a consistent explanation has been given in terms of exciton radiative recombination on trap states at the interface between Si dot and silicate matrix. Electrical measurements have given evidence for an expected material anisotropy where large difference between lateral and perpendicular resistivity values has been found. A technological strategy for transport property improvement has been prospected. (C) 2014 Elsevier B.V. All rights reserved.