Modified spontaneous emission of silicon nanocrystals embedded in artificial opals

Abstract

Si nanocrystals (NCs) were embedded in synthetic silica opals by means of Si-ion implantation or opal impregnation with porous-Si suspensions. In both types of sample photoluminescence (PL) is strongly Bragg-reflection attenuated (up to 75%) at the frequency of the opal stop-band in a direction perpendicular to the (1 1 1) face of the perfect hcp opal structure. Time-resolved PL shows a rich distribution of decay rates, which contains both shorter and longer decay components compared with the ordinary stretched exponential decay of Si NCs. This effect reflects changes in the spontaneous emission rate of Si NCs due to variations in the local density of states of real opal containing defects.

Photoluminescence of nanoporous silicon grains in TiO2 matrices

“…At the initial stage the decay gets substantially faster but at longer time delays a slight deceleration of the decay can be recognized. Exactly the same characteristic behaviour has been observed recently in artificial SiO 2 opals doped with Si-ncs [15] and interpreted as the effect of the stop-band on the spontaneous emission of Si-ncs. More specifically, the faster decay is considered to be a consequence of defects in disordered regions of the inverse opal (increased density of photon states) while the slower decay occurs in unperturbed regions of the opal (lowered density of photon states).…”

Silicon quantum dots: surface matters

“…With highly monodispersive SiQDs, more advanced self-assembled structures can be obtained, such as binary superlattices with gold nanoparticles [125]. Complex superstructures can also be achieved via a controlled growth in pre-defined superstructures, such as opals [126,127], zeolites [128,129], or periodic mesoporous silica [130,131]. Embedding SiQDs in chemically resistant polymer hybrids is yet another very interesting technique [132].…”

The Synthesis of Silicon Nanocrystals by Ion Implantation

“…For the implantation conditions employed, nanocrystals were formed only in the top-three sphere layers, but the resulting nanocrystal luminescence showed clear stop bands associated with the regular photonic crystal structure [63]. For example, Si nanocrystals have been formed within a regular 3D array of silica spheres (artificial opal) by ion implantation and annealing.…”