Compact Morphology Research Articles

Enhanced thermoelectric power factor in in-situ high-vacuum annealed Bi1-xSbx films with compact morphology by magnetron sputtering

Thermoelectric performances of thin films are affected by both the morphology and composition of the films. On one hand, the compact morphology of films could increase electrical conductivity via boosting carrier mobility. On the other hand, for semimetal or semiconductor materials, alloying is an effective means to adjust the carrier concentration and band structure and further modulate thermoelectric performances. In this work, with an in-situ high-vacuum annealing technique, we prepared compact Bi1-xSbx thin films via magnetron sputtering and further modulated their power factor by varying Sb content. Thermoelectric transport measurements revealed an enhanced room-temperature power factor up to 23.48 μW/(cmK2) in compact Bi0.95Sb0.05 film with high carrier mobility. Our simulation results based on a tight-binding model, in conjunction with the experimentally observed mobility peak, suggest that the observation of enhanced thermoelectric power factor is possibly related to the composition-induced band structure modulation.

Self‐Patterned CsPbBr3 Nanocrystal Based Plasmonic Hot‐Carrier Photodetector at Telecommunications Wavelengths

AbstractExtending the photodetection range of lead halide perovskites into the near‐infrared telecommunications bands can not only enable a wide‐spectrum solar energy harvesting, but pave ways for important applications in biodetection, infrared imaging, and telecommunication. However, there is a lack of an effective means to apply lead halide perovskites for efficient photodetection covering a wide wavelength range in the telecommunications bands. Here, CsPbBr3 nanocrystal‐ (NC‐) based photodetector operating at wavelengths in the telecommunications bands via surface plasmon‐induced hot holes is demonstrated. The internal photoemission of the plasmon‐induced hot holes from plasmonic antennas into CsPbBr3 NCs enables a photocurrent at wavelengths around 1550 nm. Moreover, a solvent treatment is also performed on drop‐casted CsPbBr3 NC thin film leading to a nanoscale self‐patterning with a compact and uniform morphology. This treatment benefits the carrier transportation contributing to a detectable photoresponse and minimizes the optical scattering so that the CsPbBr3 NCs can be integrated into the plasmonic structure without damping its resonant feature. Consequently, the CsPbBr3 NC‐based plasmonic hot‐carrier device achieves polarization discrimination and wavelength‐selective photodetection without additional optical components.

Efficient and Stable Quasi‐2D Perovskite Solar Cells Enabled by Thermal‐Aged Precursor Solution

AbstractQuasi‐2D perovskites have received wide attention in photovoltaics owing to their excellent materials robustness and merits in the device stability. However, the highest power conversion efficiency (PCE) reported on quasi‐2D perovskite solar cells (PSCs) still lags those of the 3D counterparts, mainly caused by the relatively high voltage loss. Here, a study is presented on the mitigation of voltage loss in quasi‐2D PSCs via usage of thermal‐aged precursor solutions (TAPSs). Based on the (AA)2MA4Pb5I16 (n = 5) quasi‐2D perovskite absorber with a bandgap of ≈1.60 eV, a record‐high open‐circuit voltage of 1.24 V is obtained, resulting in boosting the PCE to 18.68%. The enhanced photovoltaic performance afforded by TAPS is attributed to the thermal‐aged solution processing that triggers colloidal aggregations to reduce the nucleation sites inside the solution. As a result, formation of high‐quality perovskite films featuring compact morphology, preferential crystal orientation, and lowered trap density is allowed. Of importance, with the improved film quality, the corrosion of Ag electrode induced by ion migrations is effectively restrained, which leads to a satisfactory storage stability with <2% degradation after 1200 h under nitrogen environment without encapsulation.

Root Architecture, Growth and Photon Yield of Cucumber Seedlings as Influenced by Daily Light Integral at Different Stages in the Closed Transplant Production System

Optimizing light conditions for vegetable seedling production in a closed transplant production system is critical for plant growth and seedling production. Additionally, energy use efficiency should be considered by growers when managing the light environment. In the present study, cucumber seedlings (Cucumis sativus L. cv. Tianjiao No. 5) were grown under six different daily light integrals (DLIs) at 8.64, 11.52, 14.40, 17.28, 23.04, and 28.80 mol m−2 d−1 created by two levels of photosynthetic photon flux density (PPFD) of 200 and 400 μmol m−2 s−1 combined with photoperiod of 12, 16 and 20 h d−1 provided by white light-emitting diodes (LEDs) in a closed transplant production system for 21 days. Results indicated that quadratic functions were observed between fresh and dry weights of cucumber seedlings and DLI at 6, 11, 16, and 21 days after sowing. Generally, higher DLI resulted in longer root length, bigger root volume and root surface area accompanied with shorter plant height and hypocotyl length; however, no significant differences were observed in root length, root volume, and root surface area as DLI increased from 14.40 to 28.80 mol m−2 d−1. Photon yield based on fresh and dry weights decreased with increasing DLI. In conclusion, increased DLI resulted in compact and vigorous morphology but reduced photon yield of cucumber seedlings produced in a closed transplant production system. In terms of plant growth and energy use efficiency, DLI at 14.40–23.04 mol m−2 d−1 was suggested for cucumber seedling production in the closed production system. Additionally, different control strategies should be applied at different growth stages of cucumber seedlings.

Condensation tendency and planar isotropic actin gradient induce radial alignment in confined monolayers.

A monolayer of highly motile cells can establish long-range orientational order, which can be explained by hydrodynamic theory of active gels and fluids. However, it is less clear how cell shape changes and rearrangement are governed when the monolayer is in mechanical equilibrium states when cell motility diminishes. In this work, we report that rat embryonic fibroblasts (REF), when confined in circular mesoscale patterns on rigid substrates, can transition from the spindle shapes to more compact morphologies. Cells align radially only at the pattern boundary when they are in the mechanical equilibrium. This radial alignment disappears when cell contractility or cell-cell adhesion is reduced. Unlike monolayers of spindle-like cells such as NIH-3T3 fibroblasts with minimal intercellular interactions or epithelial cells like Madin-Darby canine kidney (MDCK) with strong cortical actin network, confined REF monolayers present an actin gradient with isotropic meshwork, suggesting the existence of a stiffness gradient. In addition, the REF cells tend to condense on soft substrates, a collective cell behavior we refer to as the 'condensation tendency'. This condensation tendency, together with geometrical confinement, induces tensile prestretch (i.e. an isotropic stretch that causes tissue to contract when released) to the confined monolayer. By developing a Voronoi-cell model, we demonstrate that the combined global tissue prestretch and cell stiffness differential between the inner and boundary cells can sufficiently define the cell radial alignment at the pattern boundary.

Dendritic WS2 Nanocrystal-Coated Monolayer WS2 Nanosheet Heterostructures for Phototransistors

Two-dimensional tungsten disulfide (WS2), as one of the widely concerned members of the transition metal dichalcogenides family, has been studied broadly by its outstanding photonic and electronic properties. Since all of the research works focus on size and the number of layers, the dendritic structure WS2 has been scarcely reported. In our study, we make use of atmospheric pressure chemical vapor deposition (APCVD) to control the synthesis of dendritic WS2/monolayer WS2 heterostructures on the SiO2/Si substrate. The stacking morphology of the heterostructure is verified by AFM, Raman, and PL spectra. The effects of growth times and carrier gas flux on the quasi-epitaxial growth of WS2 films with dendritic structures have been systematically studied. In addition, the transition between fractal, dendritic, and compact morphologies with the increase of the growth times (carrier gas flux) are more significant. The compact morphology and difference of contact potential between the adjacent dendritic structures are characterized by Kelvin probe force microscopy (KPFM). Moreover, the as-fabricated FET devices exhibit excellent electronic properties (on/off ratio, carrier mobility, photoresponsivity, and response time are about 106, 11.42 cm2 V–1S1–, 46.6 mA/W, and 105.5 μs, respectively). This study paves the way for the rational design of high-sensitivity fractal-enhanced phototransistor devices for industrial and commercial applications.

Exploiting the Combination of Displacement and Chemical Plating for a Tailored Electroless Deposition of Palladium Films on Copper

Various formulations for electroless deposition, to obtain continuous nanometre-sized and micrometre-sized films of palladium on copper, were compared. We deposited ultrathin films using displacement plating formulations. We obtained continuous films with an equivalent thickness between 6 and 22 nm, measured by exploiting the K-ratio method with SEM-EDS of Pd layers. The Pd films obtained in this step of the work represent a cost-effective catalytic substrate. As a second step, we selected chemical plating as the procedure to obtain palladium films with a thickness in the micrometre range. An ammonia-based Pd chemical plating bath represent one of the most effective chemical plating formulations. To prevent copper substrates from being damaged by ammonia, displacement plating with palladium was also applied as a pre-treatment to make the use of these plating baths a viable way to obtain thicker palladium coatings. Palladium films showing good adherence, compact morphology, and a thickness over 1.5 μm were obtained, proving that the combination of two different electroless techniques was the key to develop a sustainable procedure for micrometre-sized palladium coatings, which could substitute electroplating of Pd in galvanic industry for decorative applications.

The low temperature pyrolysis preparation of In2S3 thin film and its application in Sb2S3 thin film solar cells

In2S3 thin films were successfully prepared by the low temperature pyrolysis of indium-butyldithiocarbamate (In-BDCA) complex at 200 °C for 30 min and first applied as the electron transport layer in Sb2S3 thin film solar cells. The influence of the In-BDCA complex content in the precursor solution on the microstructure of the In2S3 thin films was investigated and the photovoltaic performance of the corresponding Sb2S3 thin film solar cells was evaluated. The result revealed that In2S3 thin film with 2:1 possessed compact and full-coverage surface morphology and its thickness was 25 nm. The corresponding Sb2S3 thin film solar cells achieved the photoelectric conversion efficiency (PCE) of 2.87% with the open-circuit voltage (Voc) of 0.60 V, short-circuit current density (Jsc) of 10.38 mA cm−2, fill factor (FF) of 46.40%. When the preparation temperature of Sb2S3 thin films increased from 200 °C to 300 °C, the corresponding Sb2S3 thin film solar cells achieved the PCE of 4.03% with the Voc of 0.66 V, Jsc of 12.56 mA cm−2, FF of 48.63%. This result demonstrated that the In2S3 thin film can be applied as the efficient electron transport layer in Sb2S3 thin film solar cells.

Effect of Melt Overheating on Structure and Mechanical Properties of Al-Mg-Si Cast Alloy

The paper discusses the complex effect of melt overheating with subsequent fast cooling down to the pouring temperature on the crystallization process, microstructure and mechanical properties of Al-Mg-Si aluminum alloy. The results obtained facilitated the establishment of rational modes of melt overheating, leading to a significant change in the dispersion and morphology of structural components. In particular, with an increase in the melt overheating temperature to 900 °C with holding and subsequent rapid cooling to the casting temperature, a decrease in the average size of dendritic cells of the aluminum solid solution from 39 μm to 13 μm was observed. We also noticed the refinement of eutectic inclusions of the Mg2Si phase with compact morphology. An increased level of mechanical properties was noted; the maximum values of tensile strength and elongation reached 228 MPa and 5.24%, respectively, which exceeded the initial values by 22.5% and 52.3%, correspondingly. The microhardness of the aluminum solid solution sequentially increased from 38.21 to 56.5 HV with an increase in the temperature during melt overheating. According to the EDS linear scanning, an increase in the superheat temperature of the melt is accompanied by an increase in the degree of saturation of the solid solution with magnesium.

Water-Soluble Conjugated Polyelectrolyte Hole Transporting Layer for Efficient Sky-Blue Perovskite Light-Emitting Diodes.

An optimized charge transporting layer (CTL) under perovskite film is crucial for efficient photoelectric devices. Here, a new water-soluble conjugated polyeletrolyte (CPE) with CH3 NH3 + (MA+ ) counterion termed as TB(MA) is used as the hole transporting layer (HTL) instead of the acidic poly(3,4-ethylenedioxythiophene):poly-styrene sulfonate (PEDOT:PSS) in sky-blue perovskite light-emitting diodes (PeLEDs). The inherent hydrophilicity of CPE enables a well-growth of quasi-2D perovskite layer with uniform and compact morphology, enhanced crystallinity with rare defect density and excellent energy transfer, resulting in a high photoluminescence quantum yield (PLQY) up to 62.0%. Especially, the MA+ counterion is able to passivate the interfacial defects in the perovskite, which optimize the interfacial compatibility between HTL and perovskite film. Finally, efficient sky-blue PeLEDs, emitting at 488nm, are fabricated with high external quantum efficiency (EQE) up to 13.5% by using CPE as HTL. In addition, due to the low-temperature processability of water-soluble CPE, an efficient flexible sky-blue PeLEDs based on PEN/ITO substrate is also obtained with high EQE of 8.3%. Using CPE as HTL is an effective strategy toward fabricating efficient blue PeLEDs.

Reducing Water Activity by Zeolite Molecular Sieve Membrane for Long-Life Rechargeable Zinc Battery.

Aqueous electrolytes offer major advantages in safe battery operation, green economy, and low production cost for advanced battery technology. However, strong water activity in aqueous electrolytes provokes a hydrogen evolution reaction and parasitic passivation on electrodes, leaving poor ion-transport in the electrolyte/electrode interface. Herein, a zeolite molecular sieve-modified (zeolite-modified) aqueous electrolyte is proposed to reduce water activity and its side-reaction. First, Raman spectroscopy reveals a highly aggressive solvation configuration and significantly suppressed water activity toward single water molecule. Then less hydrogen evolution and anti-corrosion ability of zeolite-modified electrolyte by simulation and electrochemical characterizations are identified. Consequently, a zinc (Zn) anode involves less side-reaction, and develops into a compact deposition morphology, as proved by space-resolution characterizations. Moreover, zeolite-modified electrolyte favors cyclic life of symmetric Zn||Zn cells to 4765 h at 0.8mA cm-2 , zinc-VO2 coin cell to 3000 cycles, and pouch cell to 100 cycles. Finally, the mature production technique and low-cost of zeolite molecular sieve would tremendously favor the future scale-up application in engineering aspect.

Effect of polyalphaolefin oils as a solvent in gel‐spinning of ultra‐high molecular weight polyethylene fibers

AbstractIn this work, lubricants based on polyalphaolefin with different viscosities were evaluated in the processing of UHMWPE fibers. All fibers were obtained by extrusion with 0.04 to 60 wt% of polyalphaolefin oils with different kinematic viscosities and densities (in ascending order: PAO8, PAO40, and PAO100), under screw speed of 20 to 60 rpm with a nozzle of 1.82 mm diameter. Also, n‐hexane was used to extracting the oils from UHMWPE fibers. The fibers did not undergo the drawing process. It was observed that the fibers that underwent process with PAO40 showed the highest linear density, achieving 3273 tex, indicating the orientation of the crystals in a compact morphology inside the extruder and the higher relaxation after leaving the nozzle, increasing die‐swell. Microscopic analysis revealed roughness in fiber as the insertion of PAO100 oil increased, while fibers with PAO40 proved to be more densified. In addition, the fibers processed with PAO40 have an increase in thermal stability after n‐hexane extraction, with degradation temperature Tmax of 482°C in comparison with 476°C for the neat UHMWPE.

Shaping surfaces and interfaces of 2D materials on mica with intercalating water and ethanol

Interfaces between mica and graphene, as well as the transition metal dichalcogenides (TMDCs) MoS2 and WS2, were wetted with water and ethanol, and investigated employing scanning force microscopy and molecular dynamics (MD) simulations. Below 25% RH, water wets the graphene-mica interface with labyrinthine structures, exhibiting branch widths of about 50 nm for single layers of graphene, increasing to almost an order of magnitude more for four graphene layers. At mica-TMDC interfaces, water films exhibit a transition from labyrinthine to compact morphology upon going from single- to multi-layers of the TMDCs. Ethanol films show a compact morphology at all the interfaces, regardless of the number of 2D material layers on top. The film morphologies are attributed to an equilibrium between electrostatic repulsion of preferentially oriented molecular dipoles, and the line tension of the wetted areas, which is dominated by the deformation of the 2D materials at the edges of the wet areas. The compact front of the water wetting film under multilayers of TMDCs is attributed to a much larger bending stiffness of these materials than of graphene multilayers. The thickness dependent stiffness of the 2D materials may be employed to shape their surfaces from the nano- to the micrometer scale.

Ultraflexible and Mechanically Strong Polymer/Polyaniline Conductive Interpenetrating Nanocomposite via In Situ Polymerization of Vinyl Monomer

Simultaneous enhancement of conductivity and mechanical properties for polyaniline/polymer nanocomposite still remains a big challenge. Here, a reverse approach via in situ polymerization (RIP) of vinyl monomers in waterborne polyaniline dispersion was raised to prepare conductive polyaniline (GPANI)/polyacrylate (PMB) interpenetrating polymer (GPANI-PMB) nanocomposite. GPANI/PMB physical blend was simultaneously prepared as reference. The conductive GPANI-PMB nanocomposite film with compact pomegranate-shape morphology is homogeneous, ultraflexible and mechanically strong. With incorporating a considerable amount of PMB into GPANI via the RIP method, only a slight decrease from 3.21 to 2.80 S/cm was detected for the conductivity of GPANI-PMB, while the tensile strength significantly increased from 25 to 43.5 MPa, and the elongation at break increased from 40% to 234%. The water absorption of GPANI-PMB3 after 72 h immersion decreased from 24.68% to 10.35% in comparison with GPANI, which is also higher than that of GPANI/PMB. The conductivity and tensile strength of GPANI-PMB were also much higher than that of GPANI/PMB (0.006 S/cm vs. 5.59 MPa). Moreover, the conductivity of GPANI-PMB remained almost invariable after folding 200 times, while that of GPANI/PMB decreased by almost half. This RIP approach should be applicable for preparing conventional conductive polymer nanocomposite with high conductivity, high strength and high flexibility.

Development of lead-free Cu2BiI5 rudorffite thin films for visible light photodetector application

Recently bismuth-based perovskites have gained intense research interest in the scenario of developing lead-free perovskites for optoelectronic applications. In the current work, we report a new rudorffite material, namely Cu2BiI5 as a successful lead replacement material. Cu2BiI5 thin films were fabricated via thermal evaporation of copper onto spin coated BiI3 thin films. Structure and morphology analysis revealed that the films formed were hexagonal Cu2BiI5 with compact surface morphologies. Raman spectra for Cu2BiI5 films showed distinct peaks at 44, 52, 83, and 112 cm−1 are reported for the first time. The films formed at the best condition showed nearly stoichiometric composition. Cu2BiI5 displayed direct bandgap values ranging from 1.53 to 1.74 eV suggest the potential absorption of light in the Vis-NIR region. Photodetector devices were fabricated using the Cu2BiI5 thin films and their visible light sensing was evaluated. The devices displayed stability and reproducibility towards different wavelengths of incident radiation, at a low bias of 0.2 V. The present investigation on the properties of Cu2BiI5 thin films suggests that it is a potential lead-replacement candidate for photodetector applications and solar energy harvesting.

Study of Ag[sbnd]Sb coatings prepared by non-cyanide electrodeposition

In order to improve the wear resistance and corrosion resistance of silver coating under electrical contact friction environment, AgSb coatings have been prepared via a non-cyanide electrodeposition process. The surface morphology, microstructure, microhardness, wear resistance, corrosion resistance and electrical resistivity of AgSb coatings have been studied and the effect of Sb content has been discussed. The non-cyanide electrodeposited AgSb coatings have a flatter and more compact surface morphology by comparison with the non-cyanide electrodeposited Ag coating due to the addition of KSbOC4H4O6 as Ag-plating brightener. The Ag2Sb coating prepared from the bath containing 3 g·L−1 KSbOC4H4O6 obtains the highest microhardness of 146.5 HV and best wear resistance. The electrochemical testing results show a corrosion current density of AgSb coatings range from 1.14 × 10−5 A·cm−2 to 4.20 × 10−7 A·cm−2 whereas the Ag2Sb coating achieves the best corrosion resistance.

Evolution and performance of a MgO/HA/DCPD gradient coating on pure magnesium

A composite calcium phosphate (CaPh) coating containing calcium hydrogen phosphate dihydrate (DCPD) and hydroxyapatite (HA) is fabricated on plasma electrolytic oxidized (PEO) magnesium via electro-assisted deposition. During immersion in simulated body fluid, the soluble DCPD stimulates the precipitation of HA and remains the degradability of the system, while the stable HA reinforces the corrosion resistance along with PEO layer. The morphology, thickness and corrosion property of the coating evolve remarkably with the deposition time. Various growth patterns of DCPD are presented in different period which noticeably influences the interfacial combination, as well as corrosion resistance. The composite coating after 60 min deposition shows most compact morphology and stable interfacial combination, leading to excellent corrosion resistance, apatite formation ability and cell attachment behavior.

Caltech-NRAO Stripe 82 Survey (CNSS). V. AGNs That Transitioned to Radio-loud State

Abstract A recent multiyear Caltech-NRAO Stripe 82 Survey revealed a group of objects that appeared as new radio sources after >5–20 yr of absence. They are transient phenomena with respect to the Faint Images of the Radio Sky at Twenty Centimeters survey and constitute the first unbiased sample of renewed radio activity. Here we present a follow-up, radio, optical, and X-ray study of them. The group consists of 12 sources, both quasars and galaxies with wide redshift (0.04 < z < 1.7) and luminosity ( ) distributions. Their radio properties in the first phase of activity, namely the convex spectra and compact morphology, allow them all to be classified as gigahertz-peaked spectrum (GPS) sources. We conclude that the spectral changes are a consequence of the evolution of newly born radio jets. Our observations show that over the next few years of activity the GPS galaxies keep the convex shape of the spectrum, while GPS quasars rapidly transform into flat-spectrum sources, which may result in them not being recognized as young sources. The wide range of bolometric luminosities, black hole masses, and jet powers among the transient sources indicates even greater population diversity in the group of young radio objects. We also suggest that small changes of the accretion disk luminosity (accretion rate) may be sufficient to ignite low-power radio activity that evolves on the scale of decades.

Hypereutectic Al-Ca-Mn-(Ni) Alloys as Natural Eutectic Composites

In the present paper, Natural Metal-Matrix Composites (NMMC) based on multicomponent hypereutectic Al-Ca-(Mn)-(Ni) alloys were studied in as-cast, annealed and rolled conditions. Thermo-Calc software and microstructural observations were utilised for analysing the equilibrium and actual phase composition of the alloys including correction of the Al-Ca-Mn system liquidus projection and the solid phase distribution in the Al-Ca-Mn-Ni system. A previously unknown Al10CaMn2 was discovered by both electron microprobe analysis and X-ray studies. The Al-6Ca-3Mn, Al-8Ca-2Mn, Al-8Ca-2Mn-1Ni alloys with representative NMMC structure included ultrafine Ca-rich eutectic and various small-sized primary crystals were found to have excellent feasibility of rolling as compared to its hypereutectic Al-Si counterpart. What is more, Al-Ca alloys showed comparable Coefficient of Thermal Expansion values due to enormous volume fraction of Al-based eutectic and primary intermetallics. Analysis of tensile samples’ fracture surfaces revealed that primary intermetallics may act either as stress raisers or malleable particles depending on their stiffness under deformation. It is shown that a compact morphology can be achieved by conventional casting without using any refining agents. Novel hypereutectic Al-Ca NMMC materials solidifying with the formation of Al10Mn2Ca primary compound have the best ductility and strength. We reasonably propose these materials for high-load pistons.

Engineering Chemical Vapor Deposition for Lead‐Free Perovskite‐Inspired MA3Bi2I9 Self‐Powered Photodetectors with High Performance and Stability

AbstractLead‐free perovskite‐inspired materials (PIMs) have attracted great interest in optoelectronics, as they feature electronic properties similar to mainstream lead‐based perovskites but are not burdened by the same toxicity issues. However, PIM photodetectors to date have not delivered efficiencies and stability on par with benchmark technologies. With a focus on methylammonium bismuth iodide (MA3Bi2I9)—a prominent lead‐free PIM—this study overcomes this challenge by growing the photoactive material through an engineered chemical vapor deposition (CVD) approach. While the commonplace one‐tube (1T)‐CVD approach delivers films with disconnected grains and large pinholes, a two‐tube (2T)‐CVD approach is developed that enables the growth of smoother films with superior, compact morphology. The considerable optoelectronic potential of 2T‐CVD MA3Bi2I9 films is demonstrated by realizing high‐performance self‐powered photodetectors, which deliver a responsivity and specific detectivity as high as 0.28 A W–1 and 8.8 × 1012 Jones, respectively, under UV illumination—i.e., approximately twice as large as the 1T‐CVD counterparts. Further, nonencapsulated 2T‐CVD devices exhibit considerable long‐term moisture stability, with an attenuation of their photoresponse of ≤3% over 100 days. These results demonstrate that 2T‐CVD offers a promising platform that can catalyze the development of high‐performance lead‐free perovskite‐inspired optoelectronics.