Enhanced Light Emission Research Articles

Enhanced deep ultraviolet light emission from AlGaN based nanowire with bowtie antenna array

The performance of conventional AlGaN based deep ultraviolet nanostructure has been hindered by low light emission efficiency. In this study, we demonstrate that the integration of a plasmonic aluminum (Al) bowtie antenna array with a high AlN content AlGaN based nanowire can potentially achieve a 42% and 45% enhancement in light emission at 275 nm under transverse electric (TE) and transverse magnetic (TM) polarization excitation, respectively. This enhancement is realized by carefully optimizing the nanowire diameter, as well as the size and position of the Al bowtie antenna array. The optimized dimensions of the nanowire facilitate light emission enhancement at 275 nm through dielectric resonance. Moreover, the integrated nanowire/antenna array system further increases light emission efficiency by exploiting local surface plasmon resonances. This integrated system holds promise for designing nano-photonic devices with precisely controlled responses.

Deciphering between enhanced light emission and absorption in multi-mode porphyrin cavity polariton samples

Abstract It remains unclear how the collective strong coupling of cavity-confined photons to the electronic transitions of molecular chromophore leverages the distinct properties of the polaritonic constituents for future technologies. In this study, we design, fabricate, and characterize multiple types of Fabry-Pérot (FP) mirco-resonators containing copper(II) tetraphenyl porphyrin (CuTPP) to show how cavity polariton formation affects radiative relaxation processes in the presence of substantial non-Condon vibronic coupling between two of this molecule’s excited electronic states. Unlike the prototypical enhancement of Q state radiative relaxation of CuTPP in a FP resonator incapable of forming polaritons, we find the light emission processes in multimode cavity polariton samples become enhanced for cavity-exciton energy differences near those of vibrations known to mediate non-Condon vibronic coupling. We propose the value of this detuning is consistent with radiative relaxation of Herzberg-Teller polaritons into collective molecular states coupled to the cavity photon coherently. We contrast the feature stemming from light emission from the HT polariton state with those that occur due to polariton-enhanced light absorption. Our results demonstrate the landscape of molecular and photonic interactions enabled by cavity polariton formation using complex chromophores and how researchers can design resonators to leverage these interactions to characterize and control polaritonic properties.

Enhancement of light emission of a low-resistivity silicon nanocrystal thin film: A simulational and experimental study

A silicon nanocrystal (Si NC) white light-emitting (λ = ∼400–900 nm) thin film with a relatively low resistivity of 1.6 × 104 Ω m has been prepared as an active medium for electrically driven Si light sources. The average size of Si NC is 2.4 ± 0.4 nm. To enhance the light emission efficiency of this low-resistivity Si NC thin film, approach of hydrogen passivation suitable for the traditional high-resistivity (1.2 × 107 Ω m in this work for example) red light-emitting Si NC thin film has been tried and found unavailable unfortunately. Our first principles simulation shows that Si NCs bonded to −O, −NH2, −OH, and −H ligands are responsible for red, green, and blue (RGB) primary color emissions in this white light-emitting sample, respectively. Passivation of the sample in NH3 and H2O atmosphere is then conducted, aiming to increase the number of the RGB light emitters. The light emission is significantly enhanced, with photoluminescence intensity, photoluminescence quantum yield, electroluminescence intensity, and net optical gains increased by factors of 4.6, 4.2, 4.0, and ∼3.0, respectively, after 10-day passivation. Further enhancements are expected for longer passivation.

Surface Modification of ZnO Nanotubes by Ag and Au Coatings of Variable Thickness: Systematic Analysis of the Factors Leading to UV Light Emission Enhancement.

Surface modification by plasmonic metals is one of the most promising ways to increase the band-to-band excitonic recombination in zinc oxide (ZnO) nanostructures. However, the metal-induced modulation of the UV light emission depends strongly on the production method, making it difficult to recognize the mechanism responsible for charge/energy transfer between the semiconductor and a metal. Therefore, in this study, the ZnO/Ag and Au hybrids were produced by the same, fully controlled experimental approach. ZnO nanotubes (NTs), fabricated by a template-assisted ALD synthesis, were coated by metals of variable mass thickness (1-6.5 nm thick) using the electron beam PVD technique. The deposited Ag and Au metals grew in the form of island films made of metallic nanoparticles (NPs). The size of the NPs and their size distribution decreased, while the spacing between the NPs increased as the mass of the deposited Ag and Au metals decreased. Systematic optical analysis allowed us to unravel a specific role of surface defects in ZnO NTs in the processes occurring at the ZnO/metal interface. The enhancement of the UV emission was observed only in the ZnO/Ag system. The phenomena were tentatively ascribed to the coupling between the defect-related (DL) excitonic recombination in ZnO and the localized surface plasmon resonance (LSPR) at the Ag NPs. However, the enhancement of UV light was observed only for a narrow range of Ag NP dimensions, indicating the great importance of the size and internanoparticle spacing in the plasmonic coupling. Moreover, the enhancement factors were much stronger in ZnO NTs characterized by robust DL-related emission before metal deposition. In contrast to Ag, Au coatings caused quenching of the UV emission from ZnO NTs, which was attributed to the uncoupling between the DL and LSP energies in this system and a possible formation of the ohmic contact between the Au metal and the ZnO.

LuF3: Yb3+/Tm3+@Lu6O5F8: Yb3+/Tm3+@BiOI for efficient degradation of pollutants under NIR light: Synergy of enhanced upconversion emission and efficient FRET

Effective use of near-infrared (NIR) light for photocatalysis in the solar full-spectrum remains a major challenge. Herein, LuF3: Yb3+/Tm3+@Lu6O5F8: Yb3+/Tm3+ (LYT@LOYT), which could convert NIR light into UV–visible light, was combined with BiOI to form a novel core-shell structured LuF3: Yb3+/Tm3+@Lu6O5F8: Yb3+/Tm3+@BiOI (LYT@LOYT@BiOI) upconversion photocatalyst. LOYT shell layer was grown in situ on LYT by high-temperature calcination in air, resulting in a 2.36-fold enhancement of blue light emission from the upconversion luminescent core. The tight core-shell wrapping formed by the solvothermal method achieved an efficient Förster resonance energy transfer (FRET) between LYT@LOYT and BiOI. Meanwhile, the formation of heterogeneous structure also accelerated the separation and transfer of photogenerated electron-hole pairs. As a result, under NIR and Vis-NIR irradiation, the degradation rates of LYT@LOYT(20)@BiOI for bisphenol A (BPA) were 1.24 and 1.11 times of LYT(20)@BiOI, and 1.57 and 1.30 times of BiOI, respectively. The enhanced photocatalytic activity was attributed to the expanded photoresponse range, enhanced upconversion emission, efficient energy transfer process, and excellent electron-hole pairs separation transfer efficiency. h+ and ⋅O2- were shown to be active species in the degradation process. This work provides a useful reference for the rational design of solar full-spectrum responsive photocatalysts which can efficiently utilize NIR light.

Tenfold Enhancement in Light Emission from Low‐Temperature Operational Doped OLEDs by Detrapping Super‐Long‐Lived Trapped Charges

AbstractAlthough doping organic fluorophores into host matrix is a common way to obtain high‐efficiency organic light‐emitting diodes (OLEDs), trapped charges are often observed on dopant molecules that are considered to be detrimental to the further enhancement of their photoelectric performances. Surprisingly, trapped charges with a super‐long lifetime of >2 h are detected in doped OLEDs operated at 20 K, which has never been discovered previously in the literature. However, the observations demonstrate that the longer lifetimes of these trapped charges are primarily governed by the larger spacing distances between trapped electrons and holes, rather than being solely determined by the well‐accepted energy‐level depth of trap states. More amazingly, compared with the device driven only by a conventional constant voltage source, a tenfold enhancement in light emission is achieved in low‐temperature operational doped OLEDs powered by an alternating positive and negative pulse voltage, because the applied negative pulse voltage can assist these super‐long‐lived trapped electrons and holes to detrap and then recombine with each other for producing enhanced light‐emission. Therefore, this study clarifies the dynamic behaviors of trapped charges and paves the pathway for obtaining high‐performance OLEDs working in low‐temperature circumstances such as outer‐space or aerospace fields.

Development of light-emitting Episcia lilacina leaf by applying Vibrio campbellii RMT1 and extending the glowing by CaCl2 and yeast extract.

Glowing Episcia lilacina was generated through foliar application of the bioluminescent bacterium Vibrio campbellii RMT1. Firstly, different nutrient formulas were tested, incorporating yeast extract and various inorganic salts, such as CaCl2, MgCl2, MgSO4, KH2PO4, K2HPO4, and NaCl, in order to enhance bacterial growth and light emission. The combination of 0.15% of yeast extract and 0.3% of CaCl2 in a nutrient broth (NB) + 1% NaCl medium extended light emission to 24h and resulted in higher light intensity compared to other combinations of yeast extract and inorganic salts. The peak intensity reached approximately 1.26 × 108 relative light units (RLU) at 7h. The optimal presence of inorganic salt ions likely contributed to enhanced light emission, while the yeast extract acted as a nutrient source. Secondly, the effect of proline on salt-induced stress symptoms was investigated by applying 20mM proline to the glowing plant. Additionally, a 0.5% agar nutrient was spread on the leaves prior to bacteria application to support bacterial growth and penetration. Exogenous proline application led to a significant accumulation of proline in plant cells, resulting in decreased malondialdehyde (MDA) levels. However, the proline accumulation also reduced the light intensity of the bioluminescent bacteria. This study demonstrates the potential for generating light on a living plant using bioluminescent bacteria. Further understanding of the interaction between plants and light-emitting bacteria could contribute to the development of sustainably light-emitting plants.

Enhancement of green light emission from the LiSrVO4:Tb3+ doped vanadate phosphor by charge compensation via co-doping of the alkali metal ions (Li+/Na+/K+)

Terbium (Tb3+) doped and alkali metal ions (Li+/Na+/K+) co-doped lithium strontium vanadate phosphors were synthesized by the conventional solid state reaction technique. The concentration of the dopant ions was varied in order to identify the optimum value (4 mol %). The prepared samples were characterized for their phase formation by powder XRD and their morphological characteristics were analyzed by SEM, where the latter confirmed that the particles were agglomerated with irregular shape. The elements present in the prepared samples were confirmed by the EDAX spectrum. The DR spectrum (200–700 nm) of the pure and the Tb3+ ions doped samples showed a wide band gap of 3.69 and 3.64 eV respectively. The photoluminescence spectrum of the Tb3+ ions doped vanadate phosphor, under NUV excitation (317 nm), showed its characteristics peaks at 487 nm (5D4→7F6), 544 nm (5D4→7F5), 586 nm (5D4→7F4) and 620 nm (5D4→7F3). On adding the alkali metal ions (co-doping), the luminescence intensity increased up to ∼ 2.2, 5.9, 3.7 times for the Li+, Na+ and K+ ions respectively, compared with that of the singly doped phosphor. Moreover, the thermal quenching results showed that, the representative phosphors were relatively very sensitive to temperature changes, as the temperature increased from 30 °C to 210 °C. Under ‘317 nm excitation and 544 nm emission’, the optimum phosphor showed the lifetime value in the microsecond range. In addition, the temperature dependent lifetime measurements were carried out to find the sensitivities of the prepared phosphor. The value of the relative sensitivities was calculated to be 0.44–1.07% (°C−1) in the 30 °C–170 °C temperature range. The optimal phosphor's CIE (Commission Internationale de l'Elcairage) co-ordinates were found to be x = 0.2718; y = 0.6214, which were in the greenish region. The correlated color temperature showed a cool greenish emission with high color purity. The above results reveal that, the green emitting LiSrVO4:Tb3+ phosphor can be a suitable candidate for fabricating phosphor converted white light emitting diode.

Mining reactive triplet carbonyls in biological systems.

Aliphatic triplet carbonyls can be treated as short-lived radicals, since both species share similar reactions such as hydrogen atom abstraction, cyclization, addition, and isomerization. Importantly, enzyme-generated triplet carbonyls excite triplet molecular oxygen to the highly reactive, electrophilic singlet state by resonance energy transfer, which can react with proteins, lipids, and DNA. Carbonyl triplets, singlet oxygen, and radicals are endowed with the potential to trigger both normal and pathological responses. In this paper, we present a short review of easy, fast, and inexpensive preliminary tests for the detection of transient triplet carbonyls in chemical and biological systems. This paper covers direct and indirect methods to look for triplet carbonyls based on their spectral distribution of chemiluminescence, photoproduct analysis, quenching of light emission by conjugated dienes, and enhancement of light emission by the sensitizer 9,10-dibromoanthracence-2-sulfonate ion (DBAS).

Enhancement of Visible Light Emission of Ni-Doped ZnO Sprayed Thin Films by Copper Co-Doping

Enhancement of Visible Light Emission of Ni-Doped ZnO Sprayed Thin Films by Copper Co-Doping

Quantitative analysis of the mechanism and influencing factors of mechanical fracture-induced light emission of Zr-based bulk metallic glasses

The catastrophic fracture of bulk metallic glasses (BMGs) during mechanical deformation is generally accompanied by the unique light emission with extremely high flash temperature. This seriously endangers the application of BMGs in engineering. Without suitable quantitative characterization methods, the underlying mechanism and influencing factors of light emission remain unclear. Herein, from the perspective of photometry, a spectroradiometer is used to characterize the brightness, spectrum, and color temperature of light emission from compressive fracture of Zr-based BMGs. Specifically, the brightness physical target serves as the intensity index to quantify the variation of light emission with external conditions. The atmospheric environment compression tests are conduct to reveal the underlying mechanism of light emission generation. Moreover, the influence of sample size, strain rate and material composition on light emission is quantified by the brightness. The results reveal that the light emission from the mechanical fracture of Zr-based BMGs is due to the spontaneous combustion of sample particles with a large specific surface area and a high energy density. The energy density of fractured surfaces and elemental composition of Zr-based BMGs are intenral factors that influence light emission. Increasing the sample size or reducing the strain rate can lead to an increase in energy density, resulting in enhanced light emission. The alloy elements with high oxidation exothermic enthalpy inside the material participate in the combustion reaction of particles, which also significantly increases the intensity of light emission. These findings provide useful insights into the avoidance of mechanical fracture-induced light emission in BMG engineering applications.

Investigation of the Superoxide Anion-Triggered Chemiluminescence of Coelenterazine Analogs

Reactive oxygen species (ROS), including superoxide anion, are involved in regulating various signaling pathways and are also responsible for oxidative stress. Sensing superoxide anion is of particular importance due to its biological significance. One potential approach is to use Coelenterazine as a chemiluminescent probe for the dynamic sensing of this ROS. In this study, we investigated the superoxide anion-triggered chemiluminescence of native Coelenterazine and two halogenated analogs and found that they showed a ~100-fold enhancement of light emission in aqueous solution, which was significantly reduced in methanol and nonexistent in aprotic solvents. In fact, Coelenterazine showed more intense light emission in aprotic solvents and, interestingly, although the light emission of the analogs seemed relatively unaffected by the solvents, their chemiluminescence was significantly quenched in water compared to methanol and, especially, to aprotic media. This suggests that the quenching effect observed for Coelenterazine is responsible for the differences in aqueous media, rather than an intrinsic enhanced emission by the analogs. In summary, we present Coelenterazine analogs that could serve as a basis for enhanced sensing of superoxide anion, providing information that could further our understanding of this chemiluminescent system.

Direct observation of the distribution of impurity in phosphorous/boron co-doped Si nanocrystals

Doping in Si nanocrystals is an interesting topic and directly studying the distribution of dopants in phosphorous/boron co-doping is an important issue facing the scientific community. In this study, atom probe tomography is performed to study the structures and distribution of impurity in phosphorous/boron co-doped Si nanocrystals/SiO2 multilayers. Compared with phosphorous singly doped Si nanocrystals, it is interesting to find that the concentration of phosphorous in co-doped samples can be significantly improved. Theoretical simulation suggests that phosphorous–boron pairs are formed in co-doped Si nanocrystals with the lowest formation energy, which also reduces the formation energy of phosphorous in Si nanocrystals. The results indicate that co-doping can promote the entry of phosphorous impurities into the near-surface and inner sites of Si nanocrystals, which provides an interesting way to regulate the electronic and optical properties of Si nanocrystals such as the observed enhancement of conductivity and sub-band light emission.

Enhanced light emission of germanium light-emitting-diode on 150 mm germanium-on-insulator (GOI).

Germanium-on-insulator (GOI) has emerged as a novel platform for Ge-based electronic and photonic applications. Discrete photonic devices, such as waveguides, photodetectors, modulators, and optical pumping lasers, have been successfully demonstrated on this platform. However, there is almost no report on the electrically injected Ge light source on the GOI platform. In this study, we present the first fabrication of vertical Ge p-i-n light-emitting diodes (LEDs) on a 150 mm GOI substrate. The high-quality Ge LED on a 150-mm diameter GOI substrate was fabricated via direct wafer bonding followed by ion implantations. As a tensile strain of 0.19% has been introduced during the GOI fabrication process resulting from the thermal mismatch, the LED devices exhibit a dominant direct bandgap transition peak near 0.785 eV (∼1580 nm) at room temperature. In sharp contrast to conventional III-V LEDs, we found that the electroluminescence (EL)/photoluminescence (PL) spectra show enhanced intensities as the temperature is raised from 300 to 450 K as a consequence of the higher occupation of the direct bandgap. The maximum enhancement in EL intensity is a factor of 140% near 1635 nm due to the improved optical confinement offered by the bottom insulator layer. This work potentially broadens the GOI's functional variety for applications in near-infrared sensing, electronics, and photonics.

GeSn/Ge Multiquantum-Well Vertical-Cavity Surface-Emitting p-i-n Structures and Diode Emitters on a 200 mm Ge-on-Insulator Platform

An efficient monolithically integrated light source with complementary metal-oxide-semiconductor (CMOS) compatibility remains the missing component to enable Si photonics for various applications. In particular, vertical-cavity-surface-emitting (VCSE) light sources, such as resonant cavity light-emitting diodes (RCLEDs) and vertical-cavity surface-emitting lasers (VCSELs), are strong contenders due to their compact size, circular emission profile with low beam divergence, wafer-scale fabrication compatibility, high bandwidth, and high coupling efficiency to fiber optic cables. We report the first demonstration of 8-in. wafer-scale GeSn/Ge multiple-quantum-well VCSE p-i-n structures and diodes for laser or light-emitting diode (LED) applications in Si photonics by wafer bonding and layer transfer techniques, which are challenging for all-epitaxy routes. The wafer could be 12 in. (300 mm) since the MQW gain medium is grown on a 300 mm Si wafer, and the bonding is wafer-scale. Alternative dielectric layers (SiO2/SiN/SiO2), introduced by wafer bonding, under the emitting structure, serve as the bottom mirror for the vertical cavity. The Ge0.92Sn0.08/Ge MQW layer is utilized to improve the material quality and to confine injected carriers. As a result, more than 8× enhancement of light emission due to the vertical cavity resonance was demonstrated by photoluminescence spectroscopy. Besides, the spectral purity is enhanced by the single-longitudinal-mode cavity. The intensity of light emission is insensitive to the temperature range from 4 to 300 K and even becomes stronger at higher temperatures since the stronger resonant cavity effect at higher temperatures compensates for the drop in light emission efficiency caused by nonradiative centers. The vertical cavity effect on the light emission is further verified by reflectivity spectroscopy and optical simulations. A positive gain can be achieved as indicated by optical gain calculations. Room-temperature electroluminescence and an excellent carrier injection efficiency of the MQW VCSE diode are observed, showing its potential for electrically injected RCLEDs and VCSELs.

Extended-SWIR GeSn LEDs with Reduced Footprint and Efficient Operation Power

Complementary metal oxide semiconductor-compatible short- and midwave infrared emitters are highly coveted for the monolithic integration of silicon-based photonic and electronic integrated circuits to serve a myriad of applications in sensing and communication. In this regard, the group IV germanium–tin (GeSn) material epitaxially grown on silicon (Si) emerges as a promising platform to implement tunable infrared light emitters. Indeed, upon increasing the Sn content, the bandgap of GeSn narrows and becomes direct, making this material system suitable for developing an efficient silicon-compatible emitter. With this perspective, microbridge PIN GeSn LEDs with a small footprint of 1520 μm2 are demonstrated, and their operation performance is investigated. The spectral analysis of the electroluminescence emission exhibits a peak at 2.31 μm, and it red-shifts slightly as the driving current increases. It is found that the microbridge LED operates at a dissipated power as low as 10.8 W at room temperature and just 3 W at 80 K. This demonstrated low operation power is comparable to that reported for LEDs having a significantly larger footprint reaching 106 μm2. The efficient thermal dissipation of the current design helped reduce the heat-induced optical losses, thus enhancing light emission. Further performance improvements are envisioned through thermal and optical simulations of the microbridge design. These simulations indicate that the use of GeSn-on-insulator substrate for developing a similar microbridge device is expected to improve the optical confinement toward the realization of electrically driven GeSn lasers.

Fast Neutron Irradiation on GaN-Based Light-Emitting Diodes From Near-Ultraviolet to Green Spectral Ranges

Neutron irradiation effects were compared for GaN-based multi-quantum well (MQW) light emitting diodes (LEDs) with emission wavelength in the near-ultraviolet (NUV), blue and green spectral regions. Optical output power, current-voltage and peak wavelength were analyzed in detail before and after irradiation. Three colors of LEDs showed an increase and then a decrease in optical output power with the increase of neutron fluence ranging from 1.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> to 1.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . The enhanced light emission performance is attributed to the increase of carrier injection for neutron irradiated MQWs. In addition, the formation of tunneling conductivity channels in the p-doped AlGaN electron block layer (EBL) induced by neutrons is considered as the main factor that dominates the performance degradation. Among the three colors of LEDs, the order of severity for the optical and electrical properties influenced by this medium-fluence neutron irradiation is green, blue, and NUV LEDs, in turn becoming more serious. The NUV LEDs rely heavily on the EBL due to their poor carrier confinement in relatively shallow GaN/AlGaN MQWs, so an increase of carrier injection or leakage induced by neutrons has significant influence on device performance. As the green LEDs have deep quantum wells, the strong confinement of carriers leads to their being least sensitive to neutron irradiation. So we believe that design of LEDs with deep quantum wells to enhance the carrier confinement ability will be helpful to improve their radiation tolerance. The findings not only enrich the understanding of the influence mechanism of neutron irradiated GaN-based UV/visible LEDs, but are also helpful to radiation hardened design.

Spectral properties of intermediate to high refractive index nanocubes.

Plasmonic resonances in sub-wavelength cavities, created by metallic nanocubes separated from a metallic surface by a dielectric gap, lead to strong light confinement and strong Purcell effect, with many applications in spectroscopy, enhanced light emission and optomechanics. However, the limited choice of metals, and the constraints on the sizes of the nanocubes, restrict the optical wavelength range of applications. We show that dielectric nanocubes made of intermediate to high refractive index materials exhibit similar but significantly blue shifted and enriched optical responses due to the interaction between gap plasmonic modes and internal modes. This result is explained, and the efficiency of dielectric nanocubes for light absorption and spontaneous emission is quantified by comparing the optical response and induced fluorescence enhancement of nanocubes made of barium titanate, tungsten trioxide, gallium phosphide, silicon, silver and rhodium.

Nanowire dimer optical antenna brightens the surface defects of silicon

Abstract Plasmonic hot spots located between metallic dimer nanostructures have been utilized comprehensively to achieve efficient light emission. However, different from the enhancement occurred in the plasmonic hot spot, the investigation of light emission off the hot spot on submicron scale remains challenge. In this work, we have constructed a plasmonic nanowire dimer (NWD) system to brighten the light emission of the surface defects of silicon off the hot spot on the submicron scale. The NWD can trap light through plasmonic gap, then, the excited emitter on the submicron scale can radiate light efficiently by coupling with the dipole gap plasmonic mode. Furthermore, the coupling of dipole plasmonic mode with the emitters can be tuned by changing the gap size, and then photoluminescence emission was drastically enhanced up to 126 folds. Theoretical simulations reveal the photoluminescence enhancement arises from the combination of the NWD’s high radiation efficiency, Purcell enhancement, efficient redirection of the emitted photoluminescence and the excitation enhancement. In this study, the photoluminescence signal can be effectively enhanced by placing nano-antenna patch on the detected low-quantum-efficiency emitters, which may open up a pathway toward controlling plasmonic gap mode enhanced light emission off the hot spot on submicron scale.

Defect-free ZnO nanorods with high angular distribution for enhanced excitonic emission

Low-temperature hydrothermal growth has emerged as a popular method for the fabrication of ZnO nanorods (NRs), increasing the functionality and utility of ZnO-based devices. In this work, we study the influence of growth time, temperature and seed layer on the dimensions and angular distribution of ZnO NRs. High-quality NRs with a crisscrossed 60° angular distribution have been grown with a 20–60 nm diameter and 600 nm length. We show that, within the ideal range of growth parameters, the growth time and temperature have no controllable influence on NR diameter and length, while the deposition method and size of the pre-growth deposited ZnO seeds affects diameter and NR angular alignment. We demonstrate advantages of using crisscross-aligned NRs over planar ZnO for the enhancement of ZnO excitonic emission by optical coupling with gold nanoparticles. These results can be readily adapted for applications that involve surface coating-mediated enhancement of both light emission and injection.Graphical abstract