TY - JOUR
T1 - Tuning the Bandgap Character of Quantum-Confined Si–Sn Alloyed Nanocrystals
AU - Bürkle, Marius
AU - Lozac'h, Mickaël
AU - McDonald, Calum
AU - Macias-Montero, Manuel
AU - Alessi, Bruno
AU - Mariotti, Davide
AU - Švrček, Vladimir
PY - 2020/5/26
Y1 - 2020/5/26
N2 - 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.
AB - 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.
KW - absorption measurements
KW - bandgap engineering
KW - direct bandgap nanocrystals
KW - electronic structure calculations
KW - silicon nanocrystals
KW - silicon–tin nanocrystals
UR - http://www.scopus.com/inward/record.url?scp=85082811776&partnerID=8YFLogxK
UR - https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201907210
UR - https://pure.ulster.ac.uk/en/publications/tuning-the-bandgap-character-of-quantum-confined-sisn-alloyed-nan
U2 - 10.1002/adfm.201907210
DO - 10.1002/adfm.201907210
M3 - Article
SN - 1616-301X
VL - 30
SP - 1907210
JO - Advanced Functional Materials
JF - Advanced Functional Materials
IS - 22
M1 - 1907210
ER -