Premium
Tuning the Bandgap Character of Quantum‐Confined Si–Sn Alloyed Nanocrystals
Author(s) -
Bürkle Marius,
Lozac'h Mickaël,
McDonald Calum,
MaciasMontero Manuel,
Alessi Bruno,
Mariotti Davide,
Švrček Vladimir
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201907210
Subject(s) - materials science , band gap , nanocrystal , direct and indirect band gaps , absorbance , semiconductor , density functional theory , chemical physics , phase (matter) , nanoscopic scale , quantum dot , potential well , electronic band structure , quantum , condensed matter physics , nanotechnology , optoelectronics , computational chemistry , quantum mechanics , optics , physics , chemistry
Nanocrystals in the regime between molecules and bulk give rise to unique electronic properties. Here, a thorough study focusing on quantum‐confined nanocrystals (NCs) is provided. At the level of density functional theory an approximate (quasi) band structure which addresses both the molecular and bulk aspects of finite‐sized NCs is calculated. In particular, how band‐like features emerge with increasing particle diameter is shown. The quasiband structure is used to discuss technological‐relevant direct bandgap NCs. It is found that ultrasmall Sn NCs have a direct bandgap in their at‐nanoscale‐stable α‐phase and for high enough Sn concentration (≈41%) alloyed Si–Sn NCs transition from indirect to direct bandgap semiconductors. The calculations strongly support recent experiments suggesting a direct bandgap for these systems. For a quantitative comparison many‐body GW + Bethe–Salpeter equation (BSE) calculations are performed. The predicted optical gaps are close to the experimental data and the calculated absorbance spectra compare well with the corresponding measurements.