title: Optimal surface functionalization of silicon quantum dots.
abstract: Surface functionalization is a critical step for Si nanocrystals being used as biological probes and sensors. Using density-functional tight-binding calculations, we systematically investigate the optical properties of silicon quantum dots (SiQDs) with various termination groups, including H, CH(3), NH(2), SH, and OH. Our calculations reveal that capping SiQDs with alkyl group (-Si-C-) induces minimal changes in the optical spectra, while covering the surface with NH(2), SH, and OH results in evident changes compared to hydrogenated SiQDs. The structural deformations and electronic property changes due to surface passivation were shown to be responsible for the above-described features. Interestingly, we find that the optical properties of SiQDs can be controlled by varying the S coverage on the surface. This tuning effect may have important implications in device fabrications.
authors.affiliation: Centre of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, People's Republic of China.
authors.forename: Q S
authors.initials: QS
authors.lastname: Li
authors.forename: R Q
authors.initials: RQ
authors.lastname: Zhang
authors.forename: S T
authors.initials: ST
authors.lastname: Lee
authors.forename: T A
authors.initials: TA
authors.lastname: Niehaus
authors.forename: Th
authors.initials: T
authors.lastname: Frauenheim
mesh_terms: D000478:Alkylation; D053758:Nanoparticles; D045663:Quantum Dots; D012825:Silicon / Q000737:chemistry*; D013057:Spectrum Analysis; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D012825:Silicon