title: Metallic-like bonding in plasma-born silicon nanocrystals for nanoscale bandgap engineering.
abstract: Based on ab initio molecular dynamics simulations, we show that small nanoclusters of about 1 nm size spontaneously generated in a low-temperature silane plasma do not possess tetrahedral structures, but are ultrastable. Apparently small differences in the cluster structure result in substantial modifications in their electric, magnetic, and optical properties, without the need for any dopants. Their non-tetrahedral geometries notably lead to electron deficient bonds that introduce efficient electron delocalization that strongly resembles the one of a homogeneous electron gas leading to metallic-like bonding within a semiconductor nanocrystal. As a result, pure hydrogenated silicon clusters that form by self-assembly in a plasma reactor possess optical gaps covering most of the solar spectrum from 1.0 eV to 5.2 eV depending simply on their structure and, in turn, on their degree of electron delocalization. This feature makes them ideal candidates for future bandgap engineering not only for photovoltaics, but also for many nano-electronic devices employing nothing else but silicon and hydrogen atoms.
authors: LPICM, CNRS, Ecole Polytechnique, University Paris-Saclay, 91128 Palaiseau, France. holger.vach@polytechnique.edu.
authors: Holger
authors: H
authors: Vach
authors: Department of Chemistry, Marquette University, Milwaukee, WI-53201, USA.
authors: Lena V
authors: http://orcid.org/0000-0001-9327-6679
authors: LV
authors: Ivanova
authors: Department of Chemistry, Marquette University, Milwaukee, WI-53201, USA.
authors: Qadir K
authors: QK
authors: Timerghazin
authors: LPICM, CNRS, Ecole Polytechnique, University Paris-Saclay, 91128 Palaiseau, France. holger.vach@polytechnique.edu.
authors: Fatme
authors: F
authors: Jardali
authors: LPICM, CNRS, Ecole Polytechnique, University Paris-Saclay, 91128 Palaiseau, France. holger.vach@polytechnique.edu.
authors: Ha-Linh Thi
authors: HT
authors: Le