Optoelectronic Components Research Articles

Anionic Fluorine and Cationic Niobium Codoped Tin Oxide Thin Films as Transparent Conducting Electrodes for Optoelectronic Applications

Exploration of alternatives for supplementing indium tin oxide electrode is currently trending due to scarcity of indium, leading to a steep increase in the cost of related optoelectronic components. Codoping of niobium (Nb) and fluorine (F) into SnO2 lattice as cationic and anionic dopants, respectively, is explored by spray deposition technique. A fixed 10 wt% F and varying Nb concentration from 0 to 5 wt% is incorporated into the SnO2 lattice. X‐ray diffraction reveals substitution of Nb and F into the SnO2 lattice without altering the structure. Optical transmittance is found to increase with Nb content up to 4% of Nb (77.59%), and it decreases thereafter. Scanning electron microscope and optical profiler imply a relatively smooth surface with sharp‐tipped particles which vary with Nb concentration. Sheet resistance decreases up to 3 wt% of Nb doping and increases thereafter. Contact angle measurement indicates that upon doping with Nb, the films turn hydrophilic. Among the deposited films, 4 wt% of Nb‐doped film shows the highest figure of merit of 5.01 × 10−3 Ω−1. The surface work function of the 4 wt% Nb‐doped SnO2 film is 4,687.85 meV. The optimal films are tested as electrodes in dye‐sensitized solar cells and are discussed in detail.

Photoluminescence of Silver-Doped ZnO Nanostructures

The present work reviews the results of the photoluminescence (PL) study of silver-doped ZnO nanostructures synthesized by both physical and chemical methods. ZnO is a semiconductor with a binding energy of 60 meV, which ensures efficient near-band-edge band emission at a temperature of 300K and ultraviolet emission of bulk ZnO, and ZnO has a bandgap energy of 3.37 eV at room temperature. By tuning the growth process parameters of silver-doped ZnO nanostructures, the optical properties of ZnO can be controlled for use in various optoelectronic components, biosensors, blue-emitting diodes, and even white light sensors.

Enhancement of luminous efficacy of polymer light‐emitting diodes with silver‐nanoparticles by oxygen‐plasma treatment

Silver-nanoparticles deposited on indium tin oxide (AgNPs/ITO) with different O2 -plasma treatment times are used as the anode window substrate for polymer light-emitting diodes (PLED). When AgNPs/ITO with an O2 -plasma treatment time of 10 min is used for PLED, a maximum current efficiency of 3.33 cd/A is realized, which is notably higher than that of a reference PLED (1.00 cd/A). Compared to those of the reference PLED, the mean current efficiency and electroluminescence intensity of the optimal PLED are enhanced by 3.24 times and 480%, respectively. O2 -plasma treatment is an easy method for optimizing the localized surface plasmon resonance effect of metal nanoparticles, exhibiting advantages of scalable mass production and high suitability for applications in related optoelectronic components.

Random laser emission from dye-doped polymer films enhanced by SiC nanowires

As the third-generation semiconductor electronic material, silicon carbide (SiC) has good chemical stability and mechanical properties, leading to wide use in optoelectronic components, fiber sensing and detectors. However, there are few important reports on its application in the research of random laser. Hereby, we built a polymer random laser system with SiC nanowires as a scattering medium doped with dye by the spin coating method. The effect of different SiC concentrations on random laser properties and the enhancement mechanism are studied. The lasing intensity increases and threshold decrease in large concentration SiC nanowires at the same lasing system, and the minimum threshold is 20 μJ/pulse. By increasing the SiC concentration, the mean free path of photon scattering decreases, which promotes the photon gain effect and improves the laser performance. However, when the concentration of SiC nanowires is too large, the mean free path of photon scattering decreases further, and the self-absorption of fluorescence radiation emerges. Thus, fluorescence quenching is produced, leading to a negative effect on laser performance. Furthermore, the lasing wavelength can be adjusted by tuning the SiC nanowires concentrations, reaching 14 nm. The random laser enhanced by SiC nanowires is stable and pumped repeatable, which could pave the way to promote the application of SiC and achieve low-cost and high-performance random laser.

Ferroelectrically Modulated and Enhanced Photoresponse in a Self-Powered α-In2Se3/Si Heterojunction Photodetector.

Photodetectors have been applied to pivotal optoelectronic components of modern optical communication, sensing, and imaging systems. As a room-temperature ferroelectric van der Waals semiconductor, 2D α-In2Se3 is a promising candidate for a next-generation optoelectronic material because of its thickness-dependent direct bandgap and excellent optoelectronic performance. Previous studies of photodetectors based on α-In2Se3 have been rarely focused on the modulated relationship between the α-In2Se3 intrinsic ferroelectricity and photoresponsivity. Herein, a simple integrated process and high-performance photodetector based on an α-In2Se3/Si vertical hybrid-dimensional heterojunction was constructed. Our photodetector in the ferroelectric polarization up state accomplishes a self-powered, highly sensitive photoresponse with an on/off ratio of 4.5 × 105 and detectivity of 1.6 × 1013 Jones, and it also shows a fast response time with 43 μs. The depolarization field generated by the remanent polarization of ferroelectrics in α-In2Se3 provides a strategy for enhancement and modulation of photodetection. The negative correlation was discovered because the enhancement photoresponsivity factor of ferroelectric modulation competes with the photovoltaic behavior within the α-In2Se3/Si heterojunction. Our research highlights the great potential of the high-efficiency heterojunction photodetector for future object recognition and photoelectric imaging.

Seamless Feedthroughs for Neurotechnologies Using Diffusion Processes

AbstractElectrical feedthroughs are a major part of active implantable medical devices. They are responsible for connecting the implants’ active sites with the processing electronics that are usually hermetically packaged. They deliver conductive pathways through the package wall and have to avoid premature device failure due to ingressing humidity. With decreasing device size, the requirements on the single parts increase, including the electrical feedthroughs. As conventional electrical feedthroughs rely on opening the hermetic bulk material of the package that introduce leak paths, they always raise the potential that water enters the package inside alongside these interfaces. Therefore, a proof‐of‐concept study of a new hermetic electrical feedthrough design that leaves the hermetic bulk material, that is, silicon, intact is presented. The concept is based on diffusing noble metals, Pt and Au, into the semiconductor bulk, resulting in a quasi‐localized resistance increase of the silicon. It is shown that by variation of diffusion temperature, time, the substrate cooling, and others, a parameter combination is found with which optoelectronic components can be driven through an intact silicon substrate.

Implementation of input correlation learning with an optoelectronic dendritic unit

The implementation of machine learning concepts using optoelectronic and photonic components is rapidly advancing. Here, we use the recently introduced notion of optical dendritic structures, which aspires to transfer neurobiological principles to photonics computation. In real neurons, plasticity—the modification of the connectivity between neurons due to their activity—plays a fundamental role in learning. In the current work, we investigate theoretically and experimentally an artificial dendritic structure that implements a modified Hebbian learning model, called input correlation (ICO) learning. The presented optical fiber-based dendritic structure employs the summation of the different optical intensities propagating along the optical dendritic branches and uses Gigahertz-bandwidth modulation via semiconductor optical amplifiers to apply the necessary plasticity rules. In its full deployment, this optoelectronic ICO learning analog can be an efficient hardware platform for ultra-fast control.

Optimized Design and Simulation of Optical Section in Electro-Reflective Modulators Based on Photonic Crystals Integrated with Multi-Quantum-Well Structures

In the design of photonic integrated circuits (PICs), the optical connections of the PIC surface, along with the electronic components of the chips, are significant issues. One of the optoelectronics components that utilizes these surface connections are electro-reflective modulators, consisting of an optical section and an electronic section. In this paper, a novel scheme of two-dimensional photonic crystals (PhCs) is presented for the optical and reflective sections of this device. This design is two-dimensional; thus, it has less volume than the current bulky structures. The finite element method is utilized to simulate and optimize the scheme of PhCs and gold layer parameters. Furthermore, optimization of design parameters is accomplished through the Nelder–Mead method. Moreover, the modeling and simulation of the proposed hybrid PhCs has been investigated according to the structural parameters with tolerance. These tolerances, related to the nanorods’ radius and lattice constants, are considered to justify and vindicate the fabrication technology limitations and conditions. In the “on” state of the modulator, the light transmission ratio is 98% for a 903 nm wavelength with a 45° angle of deflection and incident light, nd the bandwidth is 20 nm. For an 897 nm wavelength with a 41° angle, the transmission ratio is 95%, and the bandwidth is 7 nm.

A three-stage engineered deposition rate profile in evaporation processes for ultra-thin metallic transparent conductors

Transparent conductors are employed in many optoelectronic components such as liquid crystal displays, light-emitting diodes, and solar cells. Indium-tin-oxide (ITO) is the most common transparent conductor, which suffers from difficulties such as high annealing temperature and brittleness. One of the attractive alternative solutions is to use ultra-thin metal films (UTMFs). In this study, the electrical and optical properties of ultra-thin composite metal films have been studied in terms of the effect of simultaneous controlling of the deposition rate and the doping. A three-stage deposition process using electron-beam and thermal evaporation was purposed for the fabrication of UTMFs. The three steps are: (I) deposition of an ultra-thin seed layer, (II) a co-deposition process with a precisely engineered deposition rate during the transition of the two layers, and (III) an accelerated deposition of the metallic layer at the end. A chromium ultra-thin layer was used as a seed layer, and gold or silver metal was studied in the subsequent deposition stages. The results showed that the three-deposition process could effectively improve the percolation threshold, leading to high average transparency of ≥71% over 400–700 nm, the sheet resistance of ≤22Ω/□, and roughness of ≤0.6 nm root mean square in UTMFs samples employing gold as the metal layer, where the UTMF total thickness was ≈8.3 nm. As a proof of concept, organic light-emitting diodes (OLEDs) were fabricated employing an optimized chromium-gold UTMF and also with a witness ITO. According to the results, UTMFs based on the three-stage process, provide acceptable performance in OLEDs compared to the ones exploiting the ITO anode, indicating that such UTMFs are applicable in various optoelectronic devices.

Crosslinked reprocessable phosphor/polyurethane composite networks with thermal induced self-healing capacity and ultraviolet conducted fluorescence effect

In recent years, self-healing materials have attracted extensive attentions, however, the low elasticity have limited their applications, and it is difficult to track their healing process on macroscale. Herein covalently crosslinked polyurethane (PU) composite networks were developed with thermal induced self-healing capability and ultraviolet (UV) initiated fluorescence effect, which were synthesized by polytetrahydrofuran glycol (PTMG) as soft segment, hexamethylene diisocyanate (HDI) as hard segment, incorporating with blue phosphate (BP) of SrAl2O4 doped with Eu2+, Dy3+. The physio chemical properties and self-healing process of polyurethane were studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), atomic force microscope (AFM), optical microscope (OM), dynamic mechanical analysis (DMA) and tensile test. The results showed that the network materials were successfully developed with high elastic tensile properties. After healing at 60 °C for one hour, the PU network demonstrated a high healing efficiency and elongation at break. Moreover, the obtained hybrid networks emitted an intense blue light under UV with high fluorescent intensity to track healing process. Additionally, the synergistic effect of transesterification of dynamic hydrogen bond provided the composite networks reproducibility for recycling use. This self-healing polyester material shows promising applications in the fields of diagnostic healing and optoelectronic components.

Photonic Integrated Self-Coherent Homodyne Receiver Without Optical Polarization Control for Polarization-Multiplexing Short-Reach Optical Interconnects

Standard coherent communication technology is being introduced to short-reach optical communications to further scale the link throughput by leveraging more degrees of freedom of an optical channel. However, the cost, footprint, and power consumption of the coherent transceivers may impede its application to short-reach optical interconnects. Silicon photonics technology has realized the monolithic integration of various optoelectronic components for coherent transceivers on a single chip to lower the cost but except for a silicon laser. Heterogeneous integration has been developed to realize distributed feedback (DFB) laser sources, which are not well suited for standard coherent communication. Therefore, there is a trade-off between the receiver complexity and the cost of laser sources. Self-coherent homodyne detection as a compromising solution of coherent detection for short-reach applications has been studied to utilize the un-cooled DFB lasers. In this paper, as one realization of self-coherent homodyne detection without optical polarization control, the first integrated complementary polarization-diversity coherent receiver (C-PDCR) chip for addressing the complexity issue has been successfully demonstrated with rapid polarization tracking of remotely delivered local oscillator (LO). To the best of our knowledge, the fastest reported polarization tracking speed is achieved and reaches 9 Mrad/s with negligible performance degradation based on electronic MIMO DSP given the system symbol rate and MIMO coefficients updating conditions/algorithms for a 70-Gbaud dual-polarization (DP) PCS-64QAM signal with 630-Gb/s line rate (net rate 485 Gb/s). The maximal transmission capacity of this on-chip C-PDCR can reach 714 Gb/s (net rate 540 Gb/s over 35 GHz electrical bandwidth).

Roughness of Polished Surfaces of Optoelectronic Components Made of Polymeric Optical Materials

Roughness of Polished Surfaces of Optoelectronic Components Made of Polymeric Optical Materials

Dewetting regimes in ultra-thin nanocrystalline Ag films

Annealing-induced dewetting in ultra-thin metallic films continues to be a hot topic because of their prospects for developing versatile components in different optoelectronic applications. In this work, we present a brief but significant study about the effects of high vacuum annealing on the dewetting of sputtered ultra-thin Ag films. Results suggest that the activation threshold of different dewetting regimes is strongly dependent on the initial film thickness and annealing temperature. This enables the fabrication of Ag nanostructures with different microstructural features, which can be tuned by choosing adequate thickness and annealing conditions. This study shows that dewetting-regime engineering to achieve different Ag nanostructures can be a useful method to design optoelectronic components with perspectives to potential applications Thin-Film Solar Cells (TFSCs) and Surface-Enhanced Raman Spectroscopy (SERS).

Modelling and optimization of surface roughness in chemical mechanical polishing based on DNN-GA

The surface quality of Lithium Niobate (LiNbO3) has a significant influence on photonics and optoelectronics components. However, the prediction and optimization models of surface roughness were not accurate due to the random parameters. Hence, a prediction model of surface roughness is established based on an improved neural network, and a new method is proposed to optimize the arguments in chemical mechanical polishing (CMP) process. In the model, the structure of the neural network is optimized according to data features rather than choosing networks randomly. To improve the model accuracy, the optimal number of hidden layers is 4 and the corresponding amounts of nodes in each layer are 46, 34, 28, and 33, respectively. ReLU function is chosen as activation function. Subsequently, the relationship between surface roughness and processing parameters is built and the variation process of surface roughness is particularly considered. The accuracy and generalization ability of the model is verified by the experiments with the Mean Absolute Percentage Error (MAPE) of 6.42% and Root Mean Square Error (RMSE) of 0.403. Furthermore, the Genetic Algorithm (GA) method based on the selected model is applied to optimize processing arguments under the target surface roughness value of 0.3 nm. The accuracy of the fusion model is also validated by experiments with an error of 13.3%.

Fast measurement of surface defects on large components with dynamic phase-shifting digital holographic microscopy

The microscopic characterization of the surface defects on large opto-electronics components is essential to ensure the performance of major equipment. However, existing technology cannot achieve efficient and reliable fast cross-scale measurement due to the requirement on vertical scanning or polarization modulation for multi-frame capturing at each position. An effective approach is proposed to solve this problem, which needs to record only one interferometric hologram at each location and achieves full-area measurement by traversing over the surface. The overlapped area between adjacent regions are specified by wavefront registration and the topography in this area is obtained by two-step phase shifting and holographic reconstruction. Experimental results demonstrate that the proposed method can achieve fast and fast measurement of large specular components with high accuracy and high efficiency.

Flexible, Implantable, Pulse Oximetry Sensors: Toward Long-Term Monitoring of Blood Oxygen Saturations

Pulse oximetry is the most widespread method of monitoring heart rate and blood oxygen levels in both clinical and non-clinical settings. Current devices are ridged, bulky, and suitable only for short-term use. While the next generation of devices are moving toward wearable technologies, this focus on being unobtrusive is insufficient. To enable continuous high quality long-term monitoring, implanted devices are required. These will eliminate interference from light and sensitivity to skin pigmentation, allow enhanced performance during movement, and have no concerns around percussive damage. Here, an inexpensive, ultra-flexible pulse oximetry probe is demonstrated. The hybrid devices are fabricated on 5 µm Parylene C using laser ablation to define the circuit, and integrate small, rigid optoelectronic components. These are demonstrated in vivo on anesthetized pigs. Both transmission mode, and the novel reflection mode, are shown to be effective geometries for this. The heart rate measured by these devices shows < 2% variance from concurrent peripheral pulse oximetry measurements, along with an average variance of around 2.5% attributed predominantly to differences between central and peripheral oxygen saturations. In addition, it is shown that when implemented directly on the femoral artery, these devices record a more acute response to the variation in oxygen intake compared to the peripheral measurements. Finally, the same devices are shown to have the potential for use in monitoring venous oxygen content. This could open up the possibility of continuous monitoring of arteriovenous oxygen difference. These devices are straightforward to produce, biocompatible, and can be easily implanted during cardiovascular surgery, offering a route toward long-term implantation for continuous patient monitoring.

Heteroatomic stitching of broken WS2 monolayer with enhanced surface potential.

Sub-nanometre thick two-dimensional (2D) materials suffer from severe cracking during the high temperature chemical vapour deposition growth process. The cracking can be utilised to generate more active edges. These active edges can be stitched with a homo- or hetero-material. While the direct growth of 2D-heterostructures is mostly limited to a small fraction of outer edges of monolayer flakes, the cracked monolayers can be utilised to produce a large fraction of heterostructures. Heterostructures are important for developing multifunctional components for nanoscale electronics and optoelectronics. In this work, we demonstrate the formation of WS2-MoS2 heterostructures in large fractions by atomic stitching of cracked WS2 monolayers with the sequential growth of MoS2. Aberration-corrected scanning transmission electron microscopy and Raman spectroscopy have been utillised to probe fine details on the stitched interface between WS2 and MoS2. Growth of MoS2 domains were observed to take place at the terminating edge of cracked WS2, which then merged to form MoS2 multilayers at the cracked site. Growth of MoS2 at the opposite edges of WS2 eventually results in a MoS2-MoS2 junction with a Σ = 7 tilt boundary. Kelvin probe force microscope (KPFM) measurement from the stitched region revealed that the work function of WS2 is ∼32.46 meV higher than that of MoS2, which also closely matches with the Fermi energy difference between these two materials. With the aid of an atomic force microscope and KPFM, the surface potential width at the stitched region was found to be ∼5 times higher than the actual width of the interface, confirming the modulation of properties near the interface.

Living electronics: A catalogue of engineered living electronic components.

Biology leverages a range of electrical phenomena to extract and store energy, control molecular reactions and enable multicellular communication. Microbes, in particular, have evolved genetically encoded machinery enabling them to utilize the abundant redox-active molecules and minerals available on Earth, which in turn drive global-scale biogeochemical cycles. Recently, the microbial machinery enabling these redox reactions have been leveraged for interfacing cells and biomolecules with electrical circuits for biotechnological applications. Synthetic biology is allowing for the use of these machinery as components of engineered living materials with tuneable electrical properties. Herein, we review the state of such living electronic components including wires, capacitors, transistors, diodes, optoelectronic components, spin filters, sensors, logic processors, bioactuators, information storage media and methods for assembling these components into living electronic circuits.

Analysis and experiments on C band 200G coherent PON based on Alamouti polarization-insensitive receivers.

Passive optical network (PON) based on coherent detection has attracted a great deal of attention in recent years as a future solution for 100+ Gbps per wavelength. Particularly for 200G-PON, one of the most attractive options would be to switch to QAM transmission and coherent detection, due to its well know advantages compared to the Direct-Detection approaches used so far in PON. However, coherent technology, extensively used in core networks, has costs that are still perceived as too high for the access ecosystem. In order to perform cost reduction, some groups have studied the option of coherent polarization-independent (PI) detection, since it halves the number of optoelectronic components in the receiver front end. In this paper, we thus present a detailed simulative and experimental investigation of polarization-independent receivers to achieve 200 Gbps transmission in C band using the Alamouti polarization time block coding (PTBC). Our goal is to show what would be the system requirements in terms of optoelectronic bandwidths, laser phase noise and ultimate power budget limitations. We study two different modulation formats: quadrature phase-shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM). We also compare heterodyne and homodyne/intradyne solutions through simulations. As a summarizing result, we experimentally show that 200G PON based on 50 Gbaud-16QAM single-polarization Alamouti coded signals would be possible with today state-of-the-art coherent technologies, demonstrating an Optical Distribution Network loss above 33 dB with 25 km fiber length, a very promising result that is compliant with the PON power budget E1 class.

Studying the optical and thermal properties of Cs/ZnO and Cs/ZnO/GO hybrid nanocomposites

Green nanotechnology, defined as the synthesis or hybridization of nanomaterials with natural bioactive compounds, is a low-cost, eco-friendly, easy-to-manage and non-toxic technology. Nanocomposites have recently gained attention due to their unique characteristics and applications in the fabrication of microelectronic circuits, sensors, piezoelectric devices, optoelectronic components, fuel cells, corrosion surface passivation coatings, and catalysts. Accordingly, chitosan (Cs), a bioactive polymer, was hybridized with nanomaterials including ZnO and graphene oxide (GO) utilizing two easy, eco sustainable, and low-cost methods of preparation. All samples were analyzed using different analytical techniques. The FTIR and NMR results confirmed that the interaction between Cs, ZnO and GO occurs through the NH2 function group of Cs with ZnO and the O of the carboxyl group COOH of GO. Furthermore, the SEM data show the agglomeration generated by ZnO and GO on the Cs surface. According to the optical characterization of hybrid Cs/ZnO/GO, the one-pot preparation method achieves the lowest indirect and direct optical band gap values of 0.176 and 3.18 eV, respectively. Furthermore, it has a larger Eu = 5.46 eV value than the other samples, indicating a higher degree of disorder and high conductivity. Finally, the TGA results showed that hybridization of Cs with ZnO and Go improved the temperature decomposition and degradation of Cs by 79.9%. As a result, the one-pot approach for creating CS/ZnO/GO hybrid nanocomposite is effective for preparing Cs/ZnO/GO as an optoelectronic material.