Radiative exciton recombination and defect luminescence observed in single silicon nanocrystals

Communication: Non-radiative recombination via conical intersection at a semiconductor defect

“…Such selective quenching would result in the experimentally observed redshifted, size-insensitive PL of ensembles of oxidized Si-NCs even in the absence of emissive defects. The observation of short (nanosecond) PL lifetimes and oriented transition dipoles in single particle experiments, however, supports the existence of emissive defects in addition to the NR ones reported here, 49 and the ensemble-averaged PL is likely determined by the existence of both radiative and NR defects on the oxidized surface.…”

Scaling size of the interplay between quantum confinement and surface related effects in nanostructured silicon

“…15 The latter configuration allowed a systematic investigation of the electron-phonon coupling evidencing the role of the interfacial Si-O-Si phonons. 15,18 Recently, a method to directly measure the energy band alignment of Si NCs embedded in SiO 2 matrix was established. 19 However, the complete picture of energy band structure of this system as a function of the size of Si NCs and of the passivation properties of the Si NCs/SiO 2 interfaces is still lacking.…”

Bright trions in direct-bandgap silicon nanocrystals revealed by low-temperature single-nanocrystal spectroscopy

“…Interestingly, a similar spectral pattern was observed not only in II-VI-based semiconductor NCs 13 , being interpreted as the emission of a trion, but also by independent groups studying SiNCs, this time being assigned to phonon replicas. In particular, basically identical single-NC spectra with nanosecond dynamics were observed in both nominally SiO 2 -surface-capped SiNCs 4,22,23 and SiNCs capped with n-butyl 6 . In these cases, the low-energy satellites were identified with processes that involved the emission of a mixture of SiO 2 TO and LO phonons 22 and the Si-C stretching-vibration phonon 6 , respectively (for an overview of single-NC experiments in SiNCs, see Supplementary Table S1, Fig.…”

“…With respect to single-NC spectroscopy in SiNCs, several types of samples have already been probed by different groups 3,4,6,[18][19][20][21][22][23][24][25][26][27] . The most commonly observed spectral shape was a mixture of broader unstructured spectra and structured spectra with peaks approximately 150 meV apart.…”

“…Although trionic emission clearly cannot be observed in (oxidepassivated) indirect-bandgap SiNCs with long radiative lifetimes (.10 ms) due to competitive non-radiative Auger recombination (of the order of ns or less), it represents a feasible, interesting alternative explanation for structured single-NC spectra in SiNCs with short radiative lifetime 4,6,23 , especially because a correlation between the short radiative lifetime and structured spectra has been put forward 23 . However, such hypothesis would require further experiments in those samples to be verified, e.g., in the form of LT single-NC spectroscopy.…”