Functional Devices Research Articles

Cellulose-based water-in-salt ZnBr2 hydrogels with multiple functions for energy storage devices

A new simple preparation method for water-in-salt-type cellulose hydrogels filled with ZnBr2 is reported. The ZnBr2 hydrogel electrolyte can be applied to zinc-ion hybrid supercapacitors and Zn-Br interfacial batteries. The water-in-salt ZnBr2 hydrogel serves as a stable electrolyte for good electrochemical performance in zinc-ion hybrid supercapacitors without redox reactions and can participate in the charging/discharging process of the Zn‒Br interfacial battery through the redox reaction of halogen anions. The assembled zinc-ion hybrid supercapacitor exhibits a specific capacitance of 241.8 F g-1 at 0.5 A g-1. Furthermore, after a 10000-cycle-long charging/discharging test at 5 A g-1, the coulombic efficiency is found at nearly 100%. The interfacial battery reaches the highest energy efficiency of 66% at a current density of 3 mA cm-2 at 0–1.8 V and displays a good cycle life with an 88% average coulombic efficiency at 3 mA cm-2. This work expands the application of hydrogels and provides new possibilities for optimizing the high performance of electrolytes.

Preparation Methods and Quantum Hall Effect of Graphene

Graphene is a two-dimensional ultra-thin functional material. It has the characteristics of light weight, and it exhibits stable chemical properties. In recent years, it has become an excellent candidate material for the modification of various functional devices due to its excellent electrical performance. The performance of graphene is significantly influenced by the preparation method. Therefore, it is necessary to summarize the preparation methods of graphene. In addition, these functional devices typically operate in complex external environments, including magnetic fields, temperature fields, and electric fields. Therefore, studying the quantum Hall effect of graphene is of great significance for the use of graphene based devices. This article is written in order to provide a quicker understanding of this field. The preparation methods of graphene are briefly described. Among these methods, several industrialized methods of graphene production are also highlighted. Then, the progresses of quantum Hall effect in graphene are also presented. This work is of great significance for promoting the application of graphene based devices in complex external field environments.

The Design of Highly Reflective All-Dielectric Metasurfaces Based on Diamond Resonators

All-dielectric metasurfaces offer a low-loss alternative to plasmonic metasurfaces. We proposed the configuration for high-reflectivity all-dielectric metasurfaces based on single-crystal diamond (SCD) resonators on fused silica substrate and conducted simulations to optimize and analyze such a configuration via the FDTD solver. We utilized GMR as the design principle to select the configuration and the substrate material, and analyzed the scattering properties of a single SCD resonator by multipole decomposition. Then, we demonstrated that both the cylindrical resonators in square lattice and frustum-shaped resonators in hexagonal lattice can achieve near-unity reflectivity (>99.99%) and ultra-low absorption (<0.001%) at 795 nm, the typical alkali-metal laser wavelength. Additionally, we demonstrated that such a design is quite tolerant of fabrication errors and further supports its potential for realistic applications. To expand the functionality of such devices across multiple wavelengths, dual-band high-reflectivity metasurfaces at 744 nm and 828 nm were also designed. Our work is quite useful for designing diamond-based highly reflective mirrors, paving the way for low-loss all-dielectric reflective metasurfaces in high-power laser applications.

Topological traveling-wave radiation based on chiral edge states in photonic Chern insulators

Topological chiral edge states in photonic Chern insulators, which exhibit the one-way propagation property with reflection-free behavior and excellent robustness against perturbations, have become an important frontier in topological photonics. Currently, there have been many studies on its robust propagation behavior, but few studies have focused on its radiation properties. In developing functional photonic devices (e.g., topological antennas) for real-world applications, studying traveling-wave radiation characteristics based on chiral edge states deserves more attention. In this Letter, we propose a topological traveling-wave radiation system based on chiral edge states in photonic Chern insulators that show a steerable beam and reflection-free property. By introducing the perturbation controlled by magnetic fields, we demonstrate that exploiting a certain strength of perturbation can flexibly manipulate the radiation beam. In particular, the proposed dual-channel topological traveling-wave radiation system can not only improve the gain but also overcome the issue of impedance matching. The proposed configurations provide a novel way to manipulate topological-wave radiation and have potential applications for designing topological traveling-wave antennas with a reflection-free property.

Effect of disabling biventricular pacing in patients with left ventricular assist device and cardiac resynchronization therapy

Abstract Introduction Taking into account the mechanism of the left ventricular assist device (LVAD) function, the cardiac resynchronization therapy (CRT) seems to be unnecessary and, according to the current reports, the left ventricular lead (LVL) should be disabled. However, observation of the patients suggests that deactivation of the left ventricle (LV) pacing leads to deterioration of the patients condition and progression of the heart failure (HF) symptoms. Purpose The study aimed to determine differences in survival of the patients with LVAD and maintained or disabled CRT, including patients subjected to heart transplantation, as well differences in left and right ventricle function, kidneys and liver condition, NTproBNP value, subjective exercise tolerance and frequency of HF exacerbation before and after CRT deactivation. Methods The study group involved 55 patients with LVAD and CRT devices, including 11 patients with disabled LV pacing. The statistical analysis concerned the comparison of groups with and without biventricular stimulation as well results within the group with disabled LVL before and after its deactivation. Analyzed data included laboratory results, echocardiographic parameters, number of HF exacerbation episodes and exercise tolerance by NYHA classification. Results Total CRT period did not differ in group with maintained and disabled CRT [24 (12-36)months vs. 30 IQR(12-48)months respectively; p=0,74]. The median period of CRT deactivation was 30 IQR(12-48) months after LVAD implantation. Time from LVAD implantation to heart transplantation differed significantly between patients with and without CRT [20 IQR(9-32)months vs. 49,5 IQR(46,5-62)months respectively; p=0,003]. LV disabling was connected with a significant increase of NTproBNP [3072 IQR(2287-6636) pg/ml vs. 2133 IQR(1618-3437) pg/ml before LVL deactivation; p=0,009), without an aggravation of the exercise intolerance by NYHA classification (p=0,11) or total number of HF exacerbation episodes (p=0,72). Lack of LV pacing was not related to change of concentration of creatinine (p=0,13), AST (p=0,89, ALT (p=0,5), bilirubin (p=0,06) and albumin (p=0,69) before and after LV deactivation. Comparison of echocardiographic parameters with and without CRT did not demonstrate significant differences in LV ejection fraction (p=0,37), LV end-diastolic diameter (p=0,33), TAPSE (p=0,72) and tricuspid regurgitation degree (p=0,39). Death-free survival from LVAD implantation has not differed in patients with and without CRT(p=0,08), similarly like death-free survival from heart transplantation (p=0,56), however with tendency to better outcome of patients with CRT till 12 months after the heart transplant. Conclusion CRT does not improve general health condition as well death-free survival in LVAD recipients, including patients subjected to heart transplantation, however with tendency to better outcome of patients with CRT till 12 months after the heart transplant.Death-free surival after LVADDeath-free survival after transplant

Inverse design of polaritonic devices

Polaritons, arising from the strong coupling between excitons and photons within microcavities, hold promise for optoelectronic and all-optical devices. They have found applications in various domains, including low-threshold lasers and quantum information processing. To realize complex functionalities, non-intuitive designs for polaritonic devices are required. In this contribution, we use finite-difference time-domain simulations of the dissipative Gross–Pitaevskii equation, written in a differentiable manner, and combine it with an adjoint formulation. Such a method allows us to use topology optimization to engineer the potential landscape experienced by polariton condensates to tailor its characteristics on demand. The potential directly translates to a blueprint for a functional device, and various fabrication and optical control techniques can experimentally realize it. We inverse-design a selection of polaritonic devices, i.e., a structure that spatially shapes the polaritons into a flat-top distribution, a metalens that focuses a polariton, and a nonlinearly activated isolator. The functionalities are preserved when employing realistic fabrication constraints such as minimum feature size and discretization of the potential. Our results demonstrate the utility of inverse design techniques for polaritonic devices, providing a stepping stone toward future research in optimizing systems with complex light–matter interactions.

Complications after cardiac implantable electronic devices in patients with severe mental illness: a Danish nationwide study

Abstract Background Patients with mental illness experience higher rates of postoperative complications and mortality across several types of surgery, but knowledge is lacking in relation to cardiac implantable electronic device (CIED) implantations. Purpose Our study aimed to investigate the 7-day, 30-day, and 90-day postoperative complication rate and mortality in patients with severe mental illness compared to the general population. Methods All adult patients in Denmark with a first-time pacemaker or ICD implantation during the study period from July 1995 to December 2022 were identified using the Danish nationwide registers. Severe mental illness was defined as having a preexisting diagnosis of schizophrenia and other non-affective psychotic disorders, bipolar affective disorders or major depressive disorder. Postoperative complications were obtained as diagnosis codes possibly relating to device implantation and categorized into seven types of complications: arterial thrombosis, venous thrombosis, pneumothorax, bleeding, infection, device function problem, and death. Stratified logistic regression analyses adjusted for sex and age were used to calculate the odds of postoperative complications within 7, 30, and 90 days of device implantation. Results Among 108,790 patients who had a de novo pacemaker or ICD implantation the mean age was 73.5 (± 12.8), 37.5% were women and 3,393 (3.1%) of the patients had preexisting severe mental illness. In total, 10,690 (9.8%) patients had one or more complications within 90 days. The number of patients with severe mental illness who experienced a complication were 407 (12.0%) while it was 10,283 (9.8%) of those without severe mental illness. Odds of death (OR 1.57, 95% CI: 1.03-2.29) were higher in patients with severe mental illness 7 days postoperatively, and 30 days postoperatively odds of venous thromboembolism (OR: 1.69, 95% CI: 1.05-2.56) and death (OR: 1.62, 95% CI: 1.29-2.01) were higher in patients with severe mental illness. 90 days postoperatively odds of venous thrombosis (OR: 1.95, 95% CI: 1.37-2.70), infection (OR: 1.45, 95% CI: 1.16-1.79), and death (OR: 1.40, 95% CI: 1.19-1.65) were higher in patients with severe mental illness compared to patients without severe mental illness, while the odds of pneumothorax were lower at all three time points for patients with severe mental illness (OR 7-days: 0.49, 95% CI: 0.21-0.95). The odds of arterial thrombosis, bleeding and device function problems were similar between the two groups at all three time points. Conclusion Severe mental illness was associated with increased risk of several types of complications and death following CIED implantation. This indicates that further care and attention is needed to ensure adequate treatment of patients with severe mental illness suffering from cardiac arrhythmias.Forest plot, SMI: severe mental illness

Enhanced performance of GaN based VCSELs through graded electron-blocking layer design

Electron leakage from the active region to the p-type region restricts the performance of GaN-based Vertical-Cavity Surface-Emitting Lasers (VCSELs). AlGaN EBL can decrease the leakage current, but also raises the hole injection barrier and reduce the hole injection efficiency. Then, it is important to design EBL structures that can enhance both electron blocking and hole injection. In this study, VCSEL devices with three different EBL, basic structure Al0.6Ga0.4N EBL labeled as Device A, newly proposed 16 nm thick Al0.75–0.80Ga0.25–0.20N EBL labeled as Device B, and 18 nm thick Al0.75–0.80Ga0.25–0.20N EBL labeled as Device C, respectively, are designed and analyzed using PICS 3D simulation. Device A represents a basic VCSEL structure, while Device C incorporates a graded electron-blocking layer (EBL) with adjusted thickness. Through simulation results, it is observed that the introduction of a graded EBL in Device C leads to significant performance enhancements compared to the basic structure of Device A. Specifically, the graded EBL effectively reduces band bending and increases the electron barrier height, thereby improving carrier confinement and reducing electron leakage. Additionally, the utilize of a Graded structure in Device C aids in strain relief at the layout between the QB and EBL, resulting in improved electron-blocking capability and potentially enhanced hole transport characteristics. These findings underscore the importance of EBL grading in optimizing the performance of VCSELs, highlighting its potential for advancing the efficiency and functionality of these semiconductor devices. Power of the device C is being improved upto 4.16%, similarly the conduction band barrier height is improved upto 26.6% which is beneficial for better VCSEL performance as it enhances electron confinement in the active region, leading to increased efficiency and reduced carrier leakage and valance band barrier height decreases upto 6.52% and threshold current is decreased upto 4.8% so if valence band barrier height decrease the hole injection efficiency increases and if threshold current decreases the emitting power of the device increase.

Measurements of Stray Radiation from Medical Devices in Hospitals

The main objective of this study was to look for the electromagnetic interference produced by medical devices in hospitals and to evaluate its impacts on the proper functions of such devices. However, the present study encountered other important problems with regard to CT scanner and X-ray Imaging systems. Such problems demand fast responses in order to secure health safety for the patients and the operators of such systems. ORIGINAL RESEARCH ARTICLE | Oct. 23, 2024

2D Embedded Ultrawide Bandgap Devices for Extreme Environment Applications.

Ultrawide bandgap semiconductors such as AlGaN, AlN, diamond, and β-Ga2O3 have significantly enhanced the functionality of electronic and optoelectronic devices, particularly in harsh environment conditions. However, some of these materials face challenges such as low thermal conductivity, limited P-type conductivity, and scalability issues, which can hinder device performance under extreme conditions like high temperature and irradiation. In this review paper, we explore the integration of various two-dimensional materials (2DMs) to address these challenges. These materials offer excellent properties such as high thermal conductivity, mechanical strength, and electrical properties. Notably, graphene, hexagonal boron nitride, transition metal dichalcogenides, 2D and quasi-2D Ga2O3, TeO2, and others are investigated for their potential in improving ultrawide bandgap semiconductor-based devices. We highlight the significant improvement observed in the device performance after the incorporation of 2D materials. By leveraging the properties of these materials, ultrawide bandgap semiconductor devices demonstrate enhanced functionality and resilience in harsh environmental conditions. This review provides valuable insights into the role of 2D materials in advancing the field of ultrawide bandgap semiconductors and highlights opportunities for further research and development in this area.

Microfluidic capillary platform with hydrophilic PDMS for point-of-care immunoassays

Point-of-care (PoC) devices offer the possibility of fast and easy to use testing platforms. Self-driven capillary devices are particularly interesting because they can function without external pumps. Microfluidic devices often rely on polydimethylsiloxane (PDMS) prototyping; however, for self-driven microfluidics, its hydrophobic nature makes its use challenging. Bulk modification of PDMS through copolymers with hydrophilic moieties could be a practical solution because the copolymer is added prior to PDMS baking in a single-step process. In this work, a PDMS bulk modification with dimethylsiloxane-(60–70 % ethylene oxide) block copolymer was used to render PDMS hydrophilic. The addition of 1 % (w/w) copolymer resulted in a hydrophilic PDMS which was then used to fabricate the capillary devices. The microfluidic design included a serpentine channel with reagent entry points connected to a capillary pump and was closed by a membrane layer with conical shaped reservoirs. The reservoirs were designed to allow the sequential entry of the solutions and the device sealing and robustness were improved through PMMA frames with integrated magnets. A proof-of-concept was performed with food colouring demonstrating the capability of the device to flow the solutions sequentially. Finally, an immunoassay to detect the presence of Infliximab, a therapeutic antibody for chronic inflammatory diseases, was used to demonstrate the functionality of the capillary device. The versatility of the device was also shown by performing a fluorescent indirect immunoassay and a colorimetric indirect-ELISA for the detection of Infliximab with both approaches detecting Infliximab in the clinical range of interest (between 3 and 7 μg/mL).

Mechanical Viability and Functionality Assessment of a New Sutureless Endoluminal Microvascular Device: A Preliminary In Vivo Rabbit Study.

Our group has developed a new nitinol endoluminal self-expandable device for microvascular anastomosis. It attaches to each vessel ending with opposite directed microspikes and reaches complete expansion at body temperature, using the nitinol shape memory capacity. The main purpose of this first in vivo trial is to evaluate the mechanical viability of the device and its immediate and early functionality. A recuperation study with seven New Zealand White rabbits was designed. A 1.96 mm outer diameter prototype of the new device was placed on the right femoral artery of each rabbit. Each anastomosis was reassessed on the seventh postoperative day to reevaluate the device function. The average anastomosis time with the new device was 18 min and 45 seg (±0.3 seg). It could be easily placed in all the cases with an average of 1.14 (1) complementary stitches needed to achieve a sealed anastomosis. Patency test was positive for all the cases on the immediate assessment. On the 1 week revision surgery, patency test was negative for the seven rabbits due to blood clot formation inside the device. The new device that we have developed is simple to use and shows correct immediate functionality. On the early assessment, the presence of a foreign body in the endoluminal space caused blood clot formation. We speculate that a heparin eluting version of the device could avoid thrombosis formation. We consider that the results obtained can be valuable for other endoluminal sutureless devices.

Interface-resolved photovoltage generation dynamics and band structure evolution in a PbS quantum dot solar cell.

For directed development of solar cells using nanomaterials such as quantum dots, there is a need to understand the device function in detail. Understanding where photovoltage is generated in a device and where energy losses occur is a key aspect of this, and development of methods which can provide this information is needed. We have previously shown that time-resolved photoelectron spectroscopy of core levels can be used to follow the photovoltage dynamics at a specific interface of a lead sulfide quantum dot solar cell. Here, we use the method's selectivity and sample design to investigate the photovoltage generation in different parts of this solar cell and determine how the different layers (including the absorber layer thickness) contribute to charge separation. We show that all layers contribute to photovoltage generation and that a gold contact deposited on the quantum dots is necessary for full photovoltage generation and slow charge recombination. By combining the information obtained, we are able to experimentally follow the time evolution of the solar cell band structure during the charge separation process. Furthermore, we can identify which specific layers need to be optimized for an overall improvement of quantum dot cells. In the future, this methodology can be applied to other types of devices to provide insights into photovoltage generation mechanisms.

Multiple Conformal-Contact Transfer of Large-Area Crack-Free Transition Metal Dichalcogenide Stacks

Abstract Atomically-thin two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as an ideal platform for both physics investigation and device applications. By stacking different layers into homo- or hetero-structures, an extra degree of freedom is involved in further tuning their properties, thereby boosting scenarios in twistronics, moiré photonics and optoelectronics. However, interfacial imperfections such as contaminations and cracks, frequently occur during the layer stacking sequence and accumulate layer by layer, greatly degenerating the interface quality. In this study, we developed a multiple conformal-contact transfer method to construct TMD stacks with crack-free intrinsic interfaces. The design of a deformable buffer layer is crucial to guarantee the conformal contact and intact transfer of each layer, contributing to the successful construction of centimetre-scale TMD stacks up to 8 layers. Precise control over spatial location and interlayer twist angle is also feasibly achieved, evidenced by the stacking-dependent interlayer exciton effects in WS2-WSe2 heterostructures. This work provides a facile and precise approach for architecting 2D stacks with perfect interfaces, which will further accelerate the customized design for their device functionalization.

Detection of overhead line glass insulator condition using dual function device and deep learning approach

This paper presents a design of a multifunction smart wireless device for online condition monitoring of transmission line insulators. The proposed device can measure the insulator leakage current and take images of the high-voltage insulation. Yolov5-based models and deep convolutional neural networks (DCCN) are developed to analyze and classify the measured data and estimate the insulator's health condition. We have developed and tested a prototype of the proposed device. The device can issue a real-time warning message when a sudden change takes place in the leakage current value. The control center or smartphones receive the collected data wirelessly. We analyze the transmitted data using the developed methods to detect any anomalies and take appropriate remedial action. The performance and feasibility of the developed device are assessed through extensive experimental analysis. Results attest to the robustness of the proposed device, which is easy to install for existing and future overhead transmission line insulators.

Dye-Containing Polymers with π-Extened Diketopyrropyrrole Derivatives for Semi-Transparent Organic Photovoltaics.

Dye-containing polymers P1 (PEDPP-OT-BDT) and P2 (PEDPP-OT-BDTT) including a π-extended diketopyropyrrole (DPP) derivative and electron-rich thiophene fused ring units (4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b']dithiophene for P1 and 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene for P2) were synthesized as narrow band gap dyes. A π-extended DPP (EDPP-OT-BrPh), fragment of the polymers P1 and P2, was obtained by extending the π-conjugation of DPP using Ru(III)-catalyzed C-H and N-H activation reported by Gońka et al. in 2019, exhibiting a high quantum yield (ϕem=0.84) and small HOMO-LUMO gap (Eg=1.69 eV) due to the spatial overlap of the HOMO and LUMO orbitals. The solubility of the π-extended DPP was improved by introducing four 2-octylthophene side chains around the periphery of the planer dye moiety, while maintaining the high planarity of the dye molecule, which is essential to the function of optoelectronic devices. As a result, P1 and P2, polymerized with the π-extended DPP and BDT derivatives, exhibit carrier mobility of approximately 10-5 cm2/Vs in organic field-effect transistors (OFETs). In bulk heterojunction (BHJ) solar cells with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), they demonstrate a power conversion efficiency (PCE) of 1.0 % with an average transmittance (AVTs) of around 60 %.

Amplifying energy storage and production efficiency: Utilizing BaS3: Ni2S3: Sb2S3 synthesized from dithiocarbamate precursors for enhanced and sustainable energy solutions

During this period of increasing energy use, the scientific community and energy stakeholders have been closely monitoring electrochemical energy storage. In an attempt to enhance the functionality of charge storage devices, diethyldithiocarbamate ligand is employed as a chelating agent during the production of the novel BaS3: Ni2S3: Sb2S3. The semiconductor BaS3: Ni2S3: Sb2S3, which was made in an environmentally friendly manner, showed good photoactivity due to its 2.97 eV energy band gap and light absorption. The resultant chalcogenide had an average crystallite size of 19.69 nm and displayed outstanding crystallinity with mixed crystallographic phases. Furthermore, infrared spectroscopy was used to investigate metallic sulfide connections, and the findings indicated that they varied between 500 and 875 cm−1. This chalcogenide featured varied sites for electrochemical reactions due to its morphology. The electrochemical performance of BaS3: Ni2S3: Sb2S3 was assessed using a conventional three-electrode setup. With a specific capacitance of up to 1019.4 F g−1 and a power density of 11931.26 W kg−1, BaS3: Ni2S3: Sb2S3 has proven to be an excellent electrode material for energy storage. This remarkable electrochemical performance was further reinforced by the comparable series resistance (Rs) of 0.57 Ω. During electrocatalysis, the electrode produced an OER overpotential with a Tafel slope of 348 mV and 119 mV dec−1. In contrast, the overpotential and Tafel slope in terms of the HER activity and were 211 mV and 100 mV/dec, respectively.

Near-field strong coupling and entanglement of quantum emitters for room-temperature quantum technologies

In recent years, quantum nanophotonics has forged a rich nexus of nanotechnology with photonic quantum information processing, offering remarkable prospects for advancing quantum technologies beyond their current technical limits in terms of physical compactness, energy efficiency, operation speed, temperature robustness and scalability. In this perspective, we highlight a number of recent studies that reveal the especially compelling potential of nanoplasmonic cavity quantum electrodynamics for driving quantum technologies down to nanoscale spatial and ultrafast temporal regimes, whilst elevating them to ambient temperatures. Our perspective encompasses innovative proposals for quantum plasmonic biosensing, driving ultrafast single-photon emission and achieving near-field multipartite entanglement in the strong coupling regime, with a notable emphasis on the use of industry-grade devices. We conclude with an outlook emphasizing how the bespoke characteristics and functionalities of plasmonic devices are shaping contemporary research directives in ultrafast and room-temperature quantum nanotechnologies.

Efficient mass manufacturing of high-density, ultra-low-loss Si3N4 photonic integrated circuits

Silicon nitride (Si3N4) photonic integrated circuits (PICs) offer significant advantages over traditional silicon photonics, including low loss and superior power handling at optical communication wavelength bands. To facilitate high-density integration and effective nonlinearity, the use of thick, stoichiometric Si3N4 films is crucial. However, when using low-pressure chemical vapor deposition (LPCVD) to achieve high optical material transparency, Si3N4 films exhibit large tensile stress on the order of GPa, leading to wafer cracking that challenges mass production. Methods for crack prevention are therefore essential. The photonic Damascene process has addressed this issue, attaining record low-loss Si3N4 PICs, but it lacks control of the waveguide height, leading to large random variations of waveguide dispersion and unpredictable spectrum responses of critical functional devices such as optical couplers. Conversely, subtractive processes achieve better dimension control but rely on techniques unsuitable for large-scale production. To date, an outstanding challenge is to attain both lithographic precision and ultra-low loss in high-confinement Si3N4 PICs that are compatible with large-scale foundry manufacturing. Here, we present a single-step deposited, DUV-based subtractive method for producing wafer-scale ultra-low-loss Si3N4 PICs that harmonize these necessities. By employing deep etching of densely distributed, interconnected trenches into the substrate, we effectively mitigate the tensile stress in the Si3N4 layer, enabling direct deposition of thick films without cracking and substantially prolonged storage duration. A secondary ion mass spectrometry (SIMS) analysis reveals that these deep trenches simultaneously serve as gettering centers for metal impurities, in particular copper, thereby reducing the absorption loss in Si3N4 waveguides. Lastly, we identify ultraviolet (UV)-radiation-induced damage that can be remedied through a rapid thermal annealing. Collectively, we develop ultra-low-loss Si3N4 microresonators and 0.5-m-long spiral waveguides with losses down to 1.4 dB/m at 1550 nm with high production yield. This work addresses the long-standing challenges toward scalable and cost-effective production of tightly confined, low-loss Si3N4 PICs as used for quantum photonics, large-scale linear and nonlinear photonics, photonic computing, and narrow-linewidth lasers.

Engineering of Interface Barrier in Hybrid MXene/GaN Heterostructures for Schottky Diode Applications.

The Fermi level position at the interface of a heterostructure is a critical factor for device functionality, strongly influenced by surface-related phenomena. In this study, contactless electroreflectance (CER) was utilized for the first time to investigate the built-in electric field in MXene/GaN structures with the goal of understanding the carrier transfer across the MXene/GaN interface. Five MXenes with high work functions were examined: Cr2C, Mo2C, V2C, V4C3, and Ti3C2. The physicochemical properties of the MXene/GaN structures were analyzed by using X-ray and UV photoelectron spectroscopies. It was shown that upon the coverage of the GaN surface by all investigated MXenes, a shift in the position of the surface Fermi level occurs, consequently raising the interface barrier. Additionally, the physicochemical stability of MXenes on the GaN surface was studied after annealing the structures at 750 °C. Our findings indicate that the annealing process increases the barrier height and the ionization energies of all studied structures. Furthermore, it has been shown that removing excess MXene material from the surface did not significantly impact the built-in electric field, emphasizing the robust physicochemical stability of the MXenes on the GaN surface. To validate the potential of engineering of MXene/GaN interface barrier, Schottky diodes with MXenes exhibiting the highest barrier height (Mo2C and V2C) were demonstrated.