|Michael Sullivan Online|
First-Principles Study of Silicon Nanowire Approaching the Bulk Limit
Man-Fai Ng, Michael B. Sullivan, Shi Wun Tong, and Ping Wu
Institute of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Singapore Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore
Publication Date (Web): September 26, 2011
Nano. Lett., 2011, 11 4794-4799.
First-principles density functional theory calculations on hydrogenated silicon nanowires (SiNWs) with diameters up to 7.3 nm are carried out for comparing to experimentally relevant SiNWs and evaluating its radial doping profiles. We show that the direct band gap nature of both the small diameter <110> and <100> SiNWs fades when the diameter reaches beyond about 4 nm, where the difference of direct and indirect band gaps are close, within the experimental measurement uncertainty of +-0.1 eV, suggesting the diameter size where the gap nature transition starts. In addition, we reveal that core-surface boron (B) codoped SiNW forms more preferably at large diameter than that of the surface-surface codoped one, attributing to the lower energy configuration raised by the core B dopant at large diameter SiNW. More importantly, the diameter for such a preferential transition increases as the doping concentration decreases. Our results rationalize photoluminescent measurements and radial doping distributions of SiNWs.