Abstract
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.
Original language | English |
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Article number | 1907210 |
Pages (from-to) | 1907210 |
Number of pages | 6 |
Journal | Advanced Functional Materials |
Volume | 30 |
Issue number | 22 |
Early online date | 2 Apr 2020 |
DOIs | |
Publication status | Published (in print/issue) - 26 May 2020 |
Keywords
- absorption measurements
- bandgap engineering
- direct bandgap nanocrystals
- electronic structure calculations
- silicon nanocrystals
- silicon–tin nanocrystals
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Davide Mariotti
- School of Engineering - Professor of Plasma Science & Nanoscale Engineering
- Faculty Of Computing, Eng. & Built Env. - Full Professor
Person: Academic