Clustering/declustering of silicon nanocrystals in spin-on glass solutions

Abstract

In this work we present a procedure to extract very fine silicon nanocrystals (Si-nc) from porous silicon powder and to correlate their structural properties to their optical characteristics. The silicon nanocrystals (Si-nc) were fabricated ex situ by electrochemical etching of silicon (porous silicon) and then embedded into a silicon dioxide host matrix made of spin-on glass (SOG). This approach allows the study of Si-nc behaviour directly in the colloidal solutions (ethanol, spin-on glass silicon dioxide) by light scattering. Light scattering experiments revealed aggregation of Si-nc in such solutions. We show that these clusters can be disaggregated by adding ammonia and/or phosphorous oxide to the solution. Total disaggregation is recorded and the Si-nc size obtained corresponds to the values measured by various techniques such as HR-TEM, micro-Raman and small angle x-ray scattering. Furthermore, we show that the presence of phosphorus in the spin-on glass host matrices leads to a blue shift of the photoluminescence maxima as well as declustering the Si-nc in the spin-on glass within minutes.