Journal of Optoelectronics and Advanced Materials vol:9 issue:3 pages:721-724
Low-temperature electron spin resonance (ESR) has been used to analyze Si nanoparticles embedded in a SiO2 matrix, formed by thermal annealing of SiO/SiO2 superlattices. These structures exhibit an intense broad photoluminescence (PL) peak, the origin of which is still in dispute. Both quantum confinement and influence of defects have been proposed as possible origin but so far no convincing evidence has appeared in favor for any of the hypotheses. In an attempt to further insight, we have performed extensive ESR measurements with the view to address this controversial matter from the defect side. In initial work, the various types of naturally occurring point defects were categorized and identified, both in the as received state and after appropriate photon irradiation. Knowledge of the detailed atomic nature of the revealed defects in connection with previous work on Si/SiO2 enables us to trace down the exact location of the defects, which is a key point as the centers may pertain to various locations within the SiO/SiO2 superstructures with embedded Si nanoparticles. As a general finding, it appears that the phase-separated SiO/SiO2 superstructures are beset with a substantial density of inherent point defects (P-b type defects, D, EX and E' centers), the potential effect of which on the PL behavior is to be envisioned.