Photon management with core-shell nanowire structures.

Antireflective Si/oxide core-shell nanowire arrays (NWAs) were fabricated by galvanic etching and subsequent annealing process. The excellent light-harvesting characteristics of the core-shell NWAs, such as broadband working ranges, omnidirectionality, and polarization-insensitivity, ascribed to the smooth index transition from air to the substrates, have been demonstrated. By tuning core-shell volume ratios, we obtained enhanced light trapping regions implemented in either the planar Si underneath NWAs or the core regions of NWAs, greatly benefiting the geometry design of planar and radial p-n junction cell structures, respectively. This photon management scheme indicates the potential use in nanostructured photovoltaic applications.

Giant optical anisotropy of oblique-aligned ZnO nanowire arrays.

A combined method of modified oblique-angle deposition and hydrothermal growth was adopted to grow an optically anisotropic nanomaterial based on single crystalline ZnO nanowire arrays (NWAs) with highly oblique angles (75°-85°), exhibiting giant in-plane birefringence and optical polarization degree in emission. The in-plane birefringence of oblique-aligned ZnO NWAs is almost one order of magnitude higher than that of natural quartz. The strong optical anisotropy in emission due to the optical confinement was observed. The oblique-aligned NWAs not only allow important technological applications in passive photonic components but also benefit the development of the optoelectronic devices in polarized light sensing and emission.

Periodic Si nanopillar arrays by anodic aluminum oxide template and catalytic etching for broadband and omnidirectional light harvesting.

Large-area, periodic Si nanopillar arrays (NPAs) with the periodicity of 100 nm and the diameter of 60 nm were fabricated by metal-assisted chemical etching with anodic aluminum oxide as a patterning mask. The 100-nm-periodicity NPAs serve an antireflection function especially at the wavelengths of 200~400 nm, where the reflectance is decreased to be almost tenth of the value of the polished Si (from 62.9% to 7.9%). These NPAs show very low reflectance for broadband wavelengths and omnidirectional light incidence, attributed to the small periodicity and the stepped refractive index of NPA layers. The experimental results are confirmed by theoretical calculations. Raman scattering intensity was also found to be significantly increased with Si NPAs. The introduction of this industrial-scale self-assembly methodology for light

Outcomes of Patients With Metastatic Differentiated Thyroid Cancer After Excellent Response to Treatment.

Background: To evaluate the outcomes in differentiated thyroid cancer (DTC) patients who achieved excellent response to initial treatment and developed distant metastasis during follow-up. Methods: Thyroid cancer patients registered in Chang Gung Memorial Hospital thyroid cancer database between January 1979 and December 2019 were assessed. Results: Among 1053 DTC patients with excellent response to initial therapy, 14 (1.3%) patients developed metastatic disease during follow-up, including 6 males and 8 females with median age of 50.2 years [interquartile range (IQR), 39.9-53.7]. Nine (64.3%) patients had papillary cancer, four (28.6%) had follicular cancer, and one (7.1%) had Hürthle cell cancer. Most patients (92.9%) had stage I disease at diagnosis. The sites of metastasis were lung (71.4%), bone (7.1%), mediastinum (7.1%) and multiple sites (14.3%). With a median follow-up of 18.3 years (IQR, 14.8-23.8), 2 patients had disease-specific mortality. The 5- and 10-year disease-specific survival after the diagnosis of distant metastasis was 92% and 74%, respectively. Multiple sites of metastasis was associated with increased risk of mortality (P = 0.022). Conclusions: A small proportion of DTC patients with an excellence response to initial therapy developed distant metastasis during follow-up. Multiple organ distant metastases conferred a worse disease-specific survival.

Electronic structures of well-aligned Er-doped ZnO nanorod arrays.

Electronic structures of well-aligned Er-doped ZnO (ZnO:Er) nanorod arrays (NRAs) synthesized by a solution-based hydrothermal process were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray absorption fine structure (XAFS). HRTEM and angular dependent X-ray absorption near-edge structure analysis at O K and Zn L3 edges indicates that the spontaneous polarization is along the [0001] direction. The analysis of Er L3-edge XAFS demonstrates that the local structure around Er in the ZnO:Er NRAs was transformed from O(h) to C(4v), after annealing.

Periodic si nanopillar arrays fabricated by colloidal lithography and catalytic etching for broadband and omnidirectional elimination of Fresnel reflection.

Periodic Si nanopillar arrays (NPAs) were fabricated by the colloidal lithography combined with catalytic etching. By varying the size of colloidal crystals using oxygen plasma etching, Si NPAs with desirable diameter and fill factor could be obtained. The Fresnel reflection can be eliminated effectively over broadband regions by NPAs; i.e., the wavelength-averaged specular reflectance is decreased to 0.70% at wavelengths of 200-1900 nm. The reflectance is reduced greatly for the incident angles up to 70 degrees for both s- and p-polarized light. These excellent antireflection performances are attributed to light trapping effect and very low effective refractive indices, which can be modified by the fill factor of Si in the NPA layers.

Author Correction: High-quality AlN grown with a single substrate temperature below 1200 °C.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Nitride-Based Microarray Biochips: A New Route of Plasmonic Imaging.

The desire to improve human lives has led to striking development in biosensing technologies. While the ongoing research efforts are mostly dedicated to enhancing speed and sensitivity of the sensor, a third consideration that has become increasingly important is compactness, which is strongly desired in emergency situations and personal health management. Surface plasmon resonance imaging (SPRi) is one of the few techniques that can potentially fulfill all the three goals, considering its multiplexed assay capability. However, miniaturizing SPRi biosensors remains elusive as it entails complicated optical gears. Here, we significantly slim the architecture of SPRi devices by visualizing the varied local density of states around analytes. The unusual detection scheme is realized by building a gain-assisted SPRi with InGaN quantum wells (QWs), where the QW-plasmon coupling efficiency hinges on localized refractive index variation. This new modality abolishes the prism, the polarizer, and the beam-tracking components in the most used Kretschmann configuration without compromising the performances.

Polarization-Selecting III-Nitride Elliptical Nanorod Light-Emitting Diodes Fabricated with Nanospherical-Lens Lithography.

Current-injected elliptical nanorod light-emitting diodes (LEDs) are demonstrated to emit polarized light with a bottom-emitting configuration. The polarization ratio of the electroluminescence reaches 3.17 when the length of the minor axis for the elliptical nanorods is as small as 150 nm. Electromagnetic simulation confirms the occurrence of the polarization selectivity especially when the length of the minor axis is down to 150 nm. Light with different polarization travels at different speeds in these asymmetric elliptical nanorods. Only one polarization experiences destructive interference between the light directly from the source and the reflected light by the top metal interface. A thin light-blocking layer is incorporated to increase the polarization selectivity. It is also not recommended to infill the gap with SiO2 since the polarization selectivity will be reduced. The proposed nanorod LEDs are fabricated using top-down nanofabrication approaches by combining nanospherical-lens lithography and two-step etch processes, which are both fully compatible with current semiconductor manufacturing processes. Results in this study will help to develop a chip-level polarization-selecting LED, which will be very useful for applications that require polarized light. It is especially beneficial for applications that are not suitable for using an external polarizer or require polarized light at the individual chip level.

High-quality AlN grown with a single substrate temperature below 1200 °C.

1.5-µm AlN grown by metal-organic chemical vapor deposition (MOCVD), with a single substrate temperature of 1180 °C, exhibits atomically flat surface and the XRD (102) peak width of 427 arcsec. The results are achieved with a pulsed NH3-flow condition, serving as an alternative for the commonly used temperature-varied buffer structure, which is often complicated and time-consuming. Inserting two pulsed-NH3-flow AlN layers in the epitaxial structure not only releases the lattice strain via the formation of three-dimensional nano-islands, but also smoothens the surface with prolonged lateral migration of Al adatoms. This effective growth technique substantially simplifies the manufacture of device-quality AlN.

Exceptionally omnidirectional broadband light harvesting scheme for multi-junction concentrator solar cells achieved via ZnO nanoneedles.

GaInP/GaAs/Ge triple-junction concentrator solar cells with significant efficiency enhancement were demonstrated with antireflective ZnO nanoneedles. The novel nanostructure was attained with a Zn(NO3)2-based solution containing vitamin C. Under one sun AM 1.5G solar spectrum, conversion efficiency of the triple-junction device was improved by 23.7% via broadband improvement in short-circuit currents of 3 sub-cells after the coverage by the nanoneedles with a graded refractive index profile. The efficiency enhancement further went up to 45.8% at 100 suns. The performance boost through the nanoneedles also became increasingly pronounced in the conditions of high incident angles and the cloudy weather, e.g. 220.0% of efficiency enhancement was observed at the incident angle of 60°. These results were attributed to the exceptional broadband omnidirectionality of the antireflective nanoneedles.

Packaging Glass with a Hierarchically Nanostructured Surface: A Universal Method to Achieve Self-Cleaning Omnidirectional Solar Cells.

Fused-silica packaging glass fabricated with a hierarchical structure by integrating small (ultrathin nanorods) and large (honeycomb nanowalls) structures was demonstrated with exceptional light-harvesting solar performance, which is attributed to the subwavelength feature of the nanorods and an efficient scattering ability of the honeycomb nanowalls. Si solar cells covered with the hierarchically structured packaging glass exhibit enhanced conversion efficiency by 5.2% at normal incidence, and the enhancement went up to 46% at the incident angle of 60°. The hierarchical structured packaging glass shows excellent self-cleaning characteristics: 98.8% of the efficiency is maintained after 6 weeks of outdoor exposure, indicating that the nanostructured surface effectively repels polluting dust/particles. The presented self-cleaning omnidirectional light-harvesting design using the hierarchical structured packaging glass is a potential universal scheme for practical solar applications.

Efficiency Enhancement of InGaN-Based Solar Cells via Stacking Layers of Light-Harvesting Nanospheres.

An effective light-harvesting scheme for InGaN-based multiple quantum well solar cells is demonstrated using stacking layers of polystyrene nanospheres. Light-harvesting efficiencies on the solar cells covered with varied stacks of nanospheres are evaluated through numerical and experimental methods. The numerical simulation reveals that nanospheres with 3 stacking layers exhibit the most improved optical absorption and haze ratio as compared to those obtained by monolayer nanospheres. The experimental demonstration, agreeing with the theoretical analyses, shows that the application of 3-layer nanospheres improves the conversion efficiency of the solar cell by ~31%.

Ultrasensitive Thin-Film-Based Alx Ga1-x N Piezotronic Strain Sensors via Alloying-Enhanced Piezoelectric Potential.

Alx Ga1-x N thin-film-based piezotronic strain sensors with ultrahigh strain sensitivity are fabricated through alloying of AlN with GaN. The strain sensitivity of the ternary compound Alx Ga1-x N is higher than those of the individual binary compounds GaN and AlN. Such a high performance can be attributed to the piezoelectric constant enhancement via intercalation of Al atoms into the GaN matrix, the effect of residual strain, and a suppressed screening effect.

Bottom-Up Nano-heteroepitaxy of Wafer-Scale Semipolar GaN on (001) Si.

Semipolar {101¯1} InGaN quantum wells are grown on (001) Si substrates with an Al-free buffer and wafer-scale uniformity. The novel structure is achieved by a bottom-up nano-heteroepitaxy employing self-organized ZnO nanorods as the strain-relieving layer. This ZnO nanostructure unlocks the problems encountered by the conventional AlN-based buffer, which grows slowly and contaminates the growth chamber.

Hybrid ZnO NR/graphene structures as advanced optoelectronic devices with high transmittance.

A hybrid structure (HS) made of one-dimensional ZnO nanorods (NRs) and a two-dimensional synthesized graphene sheet was successfully constructed in this study. The uniform ZnO NRs were obtained by hydrothermal method and grown on a graphene surface that had been transferred to a polyethylene terephthalate substrate. The HS exhibited high transmittance (approximately 75%) over the visible wavelength range, even after cyclic bending with a small radius of curvature. Raman spectroscopy and Hall measurement were carried out to verify the chemical composition and electrical properties of the structure. Stable electrical conductance of the ZnO NR/graphene HS was achieved, and increase in carrier mobility decreased the resistance of the ZnO-with-graphene sheet in comparison with bare ZnO NRs.

An efficient broadband and omnidirectional light-harvesting scheme employing a hierarchical structure based on a ZnO nanorod/Si3N4-coated Si microgroove on 5-inch single crystalline Si solar cells.

We employ a ZnO nanorod/Si(3)N(4)-coated Si microgroove-based hierarchical structure (HS) for a light-harvesting scheme in 5 inch single crystalline Si solar cells. ZnO nanorods and Si microgrooves were fabricated by a simple and scalable aqueous process. The excellent light-harvesting characteristics of the HS, such as broadband working ranges and omnidirectionality have been demonstrated using external quantum efficiencies and reflectance measurements. The solar cells with the hierarchical surface exhibit excellent photovoltaic characteristics, i.e., a short-circuit current (J(SC)) of 38.45 mA cm(-2), open-circuit voltage of 609 mV and conversion efficiency of 14.04%. As incident angles increase from 0° to 60°, only 5.3% J(SC) loss is achieved by employing the hierarchical surface, demonstrating the enhanced omnidirectional photovoltaic performances, also confirmed by the theoretical analysis. A viable scheme for broadband and omnidirectional light harvesting using the HS employing microscale/nanoscale surface textures on single crystalline Si solar cells has been demonstrated.

Hierarchical structures consisting of SiO2 nanorods and p-GaN microdomes for efficiently harvesting solar energy for InGaN quantum well photovoltaic cells.

We experimentally and theoretically demonstrated the hierarchical structure of SiO(2) nanorod arrays/p-GaN microdomes as a light harvesting scheme for InGaN-based multiple quantum well solar cells. The combination of nano- and micro-structures leads to increased internal multiple reflection and provides an intermediate refractive index between air and GaN. Cells with the hierarchical structure exhibit improved short-circuit current densities and fill factors, rendering a 1.47 fold efficiency enhancement as compared to planar cells.