Dynamic transition of nanosilicon from indirect to direct-like nature by strain-induced structural relaxation

Silicon nanoclusters exhibit light emission with direct-like ns–µs time dynamics; however, they show variable synthesis and structure, optical, electronic characteristics. The widely adopted model is a core–shell in which the core an indirect tetrahedral absorbing Si phase, while shell network of re-structured H–Si–Si–H molecular emitting phases, two connected via back Si–Si bonds, exhibiting potential barrier, significantly hinders emission. We carried out first-principles atomistic computations 1-nm nanoparticle to discern variabilities. Enlarging reduces barrier monotonically finite limit not sufficient for strong proceed inducing path quenching conical crossing between excited ground states. However, enlarging found induce strain structural instability, causes relaxation that creates direct without barrier. Following emission, particle relaxes completes cycle. results also confirm pivotal role HF/H2O2 etching synthesizing core–shells affording control over network. Measurements using synchrotron laboratory UV excitation thin films particles good agreement simulation results. It plausible behind stimulated gain, or microscopic laser action, reported earlier macroscopic distributions 1- 3-nm nanoparticles.