Studies of Hot Photoluminescence in Plasmonically Coupled Silicon via Variable Energy Excitation and Temperature-Dependent Spectroscopy

Abstract

By integrating silicon nanowires (∼150 nm diameter, 20 μm length) with an Ω-shaped plasmonic nanocavity, we are able to generate broadband visible luminescence, which is induced by high order hybrid nanocavity-surface plasmon modes. The nature of this super bandgap emission is explored via photoluminescence spectroscopy studies performed with variable laser excitation energies (1.959 to 2.708 eV) and finite difference time domain simulations. Furthermore, temperature-dependent photoluminescence spectroscopy shows that the observed emission corresponds to radiative recombination of unthermalized (hot) carriers as opposed to a resonant Raman process.

Understanding the Different Exciton–Plasmon Coupling Regimes in Two-Dimensional Semiconductors Coupled with Plasmonic Lattices: A Combined Experimental and Unified Equation of Motion Approach

“…On the other hand, as the reduction of the optical mode volume is one of the critical routes to enhance the light-matter interaction strength, plasmonic systems, with their extraordinary ability to confine light far below the diffraction limit, providing useful platforms for enhancing lightmatter interactions at the nanoscale 20,[40][41][42] . Especially, localized surface plasmon resonances (LSPRs), i.e., collective electron excitations at the surface of plasmonic nanostructures, can tightly confine and consequently strongly enhance the local electric field near the vicinity of these nanostructures, resulting in ultrasmall mode volumes and thus ultrastrong light-matter interactions.…”

“…On the other hand, as the reduction of the optical mode volume is one of the critical routes to enhance the light–matter interaction strength, plasmonic systems, with their extraordinary ability to confine light far below the diffraction limit, providing useful platforms for enhancing light–matter interactions at the nanoscale. ,− Especially, localized surface plasmon resonances (LSPRs), that is, collective electron excitations at the surface of plasmonic nanostructures, can tightly confine and consequently strongly enhance the local electric field near the vicinity of these nanostructures, resulting in ultrasmall mode volumes and, thus, ultrastrong light–matter interactions. − When arranged into periodic arrays, LSPRs of individual nanostructures can couple effectively to the diffractive orders of the lattice near the Rayleigh-Wood’s condition, , that is, the incident angle at which a diffractive beam passes off the array plane, giving rise to a unique type of plasmonic resonance called surface lattice resonance (SLR). − Arising from coherent coupling between the LSPR of individual plasmonic nanoresonators and the lattice diffraction modes, SLR combines the advantages of both individual components, including strongly enhanced local E-field and small mode volumes of the LSPRs, as well as enhanced quality factor, relatively long spatial coherence and high directionality of the propagating diffraction mode. Therefore, SLRs serve as an excellent platform for studying and manipulating exciton–plasmon interactions, especially in 2D systems due to geometric compatibility. − Phenomenologically, SLRs can be explained by a coupled oscillator model (COM), in which the LSPR and the lattice diffraction modes are treated as classical harmonic oscillators coupled via a phenomenological coupling strength, g .…”

Flexible Light Emission Diode Arrays Made of Transferred Si Microwires-ZnO Nanofilm with Piezo-Phototronic Effect Enhanced Lighting

“…As Si is an indirect bandgap semiconductor, the excited charged carrier in silicon will be scattered to the electronic branch and relaxes along the electronic branch by scattering with phonons (Figure S4e). Both energy and momentum must be conserved, thus the emitted photon will have energy E . where E excited is the excitation energy, and ∑ E scattering is the total energy of all scattering phonons. The lifetime of the intraband relaxation in silicon is approximately 1 ps, while the radiative recombination occurs on a 10 ns time scale.…”

Tailoring the Spectroscopic Properties of Semiconductor Nanowires via Surface-Plasmon-Based Optical Engineering

“…97 Extensive studies on plasmonically coupled Si NWs strongly suggest that the light emission mechanism is from hot photoluminescence. 98 For this Perspective, we highlight the positive temperature dependence of the emission (Figure 4d) that demonstrates increasing luminescence intensity indicative of an indirect emission process 99 and which is opposite that of direct band gap emission 100 and several other relevant Raman scattering processes. 101,102 For further discussion and more detailed spectroscopic analysis, we refer the reader to the recent study by Aspetti et al 98 …”