English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Silicon photoluminescence and lasing have been critical issues tobreakthrough bottlenecks in the understanding of luminescence mechanisms.Unfortunately, long-standing disputes about the exciton recombination mechanismand fluorescence lifetime remain unresolved, especially about whether siliconnanocrystals (Si NCs) can realize fast direct-bandgap-like optical transitions.Here, using ground-state and excited-state density functional theory (DFT), weobtained intrinsic phonon-free optical transitions at sizes from Si22 to Si705,showing that very small Si NCs can realize a strong direct optical transition.Orbital labeling results show that this rapid transition does not come from the{\Gamma}-{\Gamma} -like transition, contrary to the conclusions from theeffective mass approximation (EMA) and that {\Gamma}-X mixing leads to aquasi-direct bandgap. This anomalous transition is particularly intense withdecreasing size (or enhancement of quantum confinement). By investigatingelectron and hole distributions generated in the optical transition, localizedstate-induced enhanced emission (LIEE) in Si NCs was proposed. Quantumconfinement (QC) distorts the excited-state electron spatial distribution bylocalizing Bloch waves into the NC core, resulting in increased hole andelectron overlap, thus inducing a fast optical process. This work resolvesimportant debates and proposes LIEE to explain the anomalous luminescence--aphase transition from weak (or none) luminescent state to strong opticaltransition, which will aid attempts at realizing high-radiative-rate NCsmaterials and application-level Si lasers.

Localized State-Induced Enhanced Intrinsic Phonon-Free Optical Transition in Silicon Nanocrystals