Polarization-Independent Light Emission Enhancement of ZnO/Ag Nanograting via Surface Plasmon Polariton Excitation and Cavity Resonance

Abstract

In this study, we observed that the photoluminescence (PL) intensity of ZnO/Ag nanogratings was significantly enhanced compared with that of a planar counterpart under illumination of both transverse magnetic (TM) and transverse electric (TE)-mode light. In the TM mode, angle-resolved reflectance spectra exhibited dispersive dips, indicating cavity resonance as well as grating-coupled surface plasmon polariton (SPP) excitation. In the TE mode, cavity resonance only was allowed, and broad dips appeared in the reflectance spectra. Strong optical field confinement in the ZnO layers, with the help of SPP and cavity modes, facilitated polarization-insensitive PL enhancement. Optical simulation results were in good agreement with the experimental results, supporting the suggested scenario.

Strong Light Confinement in Metal-Coated Si Nanopillars: Interplay of Plasmonic Effects and Geometric Resonance

“…On the Si NP array, Ag and Au thin films were deposited using an electron beam evaporator. Optical reflection spectra of the bare and metal-coated NP arrays, in visible and near-infrared wavelength range, were obtained using a homemade microspectrometer with a halogen lamp as a light source [ 12 ]. The incident beam with a spot size of 400 μm is normally incident to the NP array, and the reflected light was collected to a spectrometer via an optical fiber.…”

Plasmon-Enhanced Surface Photovoltage of ZnO/Ag Nanogratings

“…Our ZnO thin films should have numerous defects both at the surface and in the bulk because they were grown at room temperature. As a result, the photoluminescence spectra of our ZnO/Ag nanogratings exhibited strong trap-state-mediated visible emission as well as the UV emission caused by the band-to-band excitation 14 15 . The visible emission from ZnO in the energy range of 1.6–2.4 eV has been attributed to interstitial Zn ions, Zn-vacancy-related defects, oxygen vacancies, and chemisorbed oxgens 13 25 .…”

“…ZnO, a wide-bandgap semiconductor, is a strong candidate material for many applications, including transparent conducting electrodes 1 , photodetectors 2 3 4 , UV LEDs 5 , field-effect transistors 6 7 8 , sensors 9 , and energy harvesting devices 10 . Optical characterizations of metal-ZnO hybrid nanostructures have revealed interactions between SPs and charge carriers 1 11 12 13 14 15 . Such plasmonic effects can also be investigated by electrical measurements 16 , but elaborate fabrication processes are often required.…”

“…Figure 5 shows the electric field intensity, , distributions in the ZnO/Ag nanograting, as obtained by finite-difference time-domain (FDTD) simulations (Lumerical FDTD Solutions) 14 15 . The light has an incident angle of 65°, as depicted in Fig.…”

Mie Resonance-Modulated Spatial Distributions of Photogenerated Carriers in Poly(3-hexylthiophene-2,5-diyl)/Silicon Nanopillars

“…3b . The experimental spectra were obtained using a micro-spectrophotometer 27 , which enabled us to characterize the small-sized NP samples (area: 1 × 1 mm 2 ). The NP sample without P3HT exhibits lower reflection over a broad wavelength range than a bare planar Si wafer even though the surface coverage of the NPs on the sample surface is only 5%.…”