Strain-engineered silicon nanocrystals(SiNCs)have recently been shown to possess direct bandgap.Here,we report the observation of a rich structure in the single-nanocrystal photoluminescence spectra of strain-engineer...Strain-engineered silicon nanocrystals(SiNCs)have recently been shown to possess direct bandgap.Here,we report the observation of a rich structure in the single-nanocrystal photoluminescence spectra of strain-engineered direct-bandgap SiNCs in the temperature range of 9–300 K.The relationship between individual types of spectra is discussed,and the numerical modeling of spectral diffusion of the experimentally acquired spectra reveals a common origin for most types.The intrinsic spectral shape is shown to be a structure that contains three peaks,approximately 150 meV apart,each of which possesses a Si phonon substructure.Narrow spectral lines,reaching ≤ meV at 20 K,are detected.The observed temperature dependence of the spectral structure can be assigned to the radiative recombination of positively charged trions,in contrast to several previous reports linking a very similar shape to phonons in the surface capping layers.Our result serves as strong additional support for the direct-bandgap nature of the investigated SiNCs.展开更多
基金Czech Science Foundation Funding(Grant Nos.GPP204/12/P235(Katerina Kusova)and P108/12/G108(Ivan Pelant))and a L’Oreal-UNESCO for Women in Science scholarship(Katerina Kusova)are gratefully acknowledgedPart of this work was supported by the Czech-Japan collaborative project LG14246(Jan Valenta).
文摘Strain-engineered silicon nanocrystals(SiNCs)have recently been shown to possess direct bandgap.Here,we report the observation of a rich structure in the single-nanocrystal photoluminescence spectra of strain-engineered direct-bandgap SiNCs in the temperature range of 9–300 K.The relationship between individual types of spectra is discussed,and the numerical modeling of spectral diffusion of the experimentally acquired spectra reveals a common origin for most types.The intrinsic spectral shape is shown to be a structure that contains three peaks,approximately 150 meV apart,each of which possesses a Si phonon substructure.Narrow spectral lines,reaching ≤ meV at 20 K,are detected.The observed temperature dependence of the spectral structure can be assigned to the radiative recombination of positively charged trions,in contrast to several previous reports linking a very similar shape to phonons in the surface capping layers.Our result serves as strong additional support for the direct-bandgap nature of the investigated SiNCs.
