Efficient energy harvesting for applications such as radioisotope thermoelectric generators and heat-recovery systems require novel thermoelectric materials with exceptional performance. This work demonstrates thermoelectric capabilities of n-type MoS2/MoSe2 heterojunctions fabricated by scalable radiofrequency sputtering. These heterostructures demonstrated an outstanding experimental Seebeck coefficient of − 1.1 mV K−1 (ΔT = 40 K), arising from thermally activated carriers with a low activation energy of 32 meV, and estimated thermoelectric figure-of-merit (ZT) values of 1.0. Furthermore, computational calculations within framework of Density Functional Theory corroborate experimental findings allowing to elucidate a crucial role of atomic-scale in determining anisotropic thermoelectric properties. Lastly, our data indicate MoS2/MoSe2 heterojunctions are a promising material for low-cost and efficient thermoelectric for microelectronic devices. Transition metal dichalcogenides offer a rich platform to exploit overlooked thermoelectric potential for energy-recovery systems and hybrid energy harvesting. This work highlights the potential of MoS2/MoSe2 thin films for thermoelectric applications, featuring a low-cost, scalable, and excellent heterostructure formation that will guide future research in the field of energy and sustainability.

We report the design of and progress towards devices that integrate NbTiN superconducting nanowire single-photon detectors with GaAs nanophotonic devices. We show that the design is expected to achieve photon detection efficiency of 99.41% power absorption in a 10-mu m-long nanowire with minimized external coupling losses.

Tungsten trioxide (WO3) is an intrinsic n-type semiconductor that can be prepared to exhibit a piezoresponse through doping and heat treatment strategies. We report the piezoresponse in platinum-doped WO3 thin films, prepared by RF/DC cosputtering, followed by postdeposition annealing at 600 °C. Measurements using Switching Spectroscopy Piezo Force Microscopy (SS-PFM) reveal domains with different polarization orientations and hysteresis behavior, corresponding to a piezoelectric coefficient of d 33 = 97 ± 6 pmV-1. Low-angle x-ray diffraction (XRD) indicates the presence of an orthorhombic structure (β-WO3) with a Pbcn space group, while Scanning Transmission Electron Microscopy (STEM) reveals the formation of platinum nanoparticles (∼5 nm) with a cubic structure (Fm m). Atom Probe Tomography (APT) confirms the formation of Pt nanoparticles and Ar-enriched cavities within the WO3 matrix induced by the annealing process. These structural modifications create lattice strain, giving rise to piezoelectric domains with different polarization orientations.

We report on monolithic integration of InP-based whistle-geometry microring lasers (WRLs) with distributed-Bragg-reflector (DBR) lasers for strong injection locking. Preliminary characterization results indicate rich interaction dynamics of the coupled WRL-DBR laser system.

Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics, and as a means of revealing or even inducing broken symmetries. Emerging methods for light-based current control offer promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. However, optical generation and manipulation of currents at nanometer spatial scales remains a basic challenge and a crucial step towards scalable optoelectronic systems for microelectronics and information science. Here, we introduce vectorial optoelectronic metasurfaces in which ultrafast light pulses induce local directional charge flows around symmetry-broken plasmonic nanostructures, with tunable responses and arbitrary patterning down to sub-diffractive nanometer scales. Local symmetries and vectorial current distributions are revealed by polarization- and wavelength-sensitive electrical readout and terahertz (THz) emission, while spatially-tailored global currents are demonstrated in the direct generation of elusive broadband THz vector beams. We show that in graphene, a detailed interplay between electrodynamic, thermodynamic, and hydrodynamic degrees of freedom gives rise to rapidly-evolving nanoscale driving forces and charge flows under extreme temporal and spatial confinement. These results set the stage for versatile patterning and optical control over nanoscale currents in materials diagnostics, THz spectroscopies, nano-magnetism, and ultrafast information processing.

Photonic integrated circuit comprising a whistle-geometry ring laser, injecting waveguide, distributed-Bragg reflector master laser, outcoupling waveguides, and a monitoring ring photodetector has been fabricated and characterized.

High-aspect-ratio micro- and nanostructures play a pivotal role across diverse technological domains, encompassing microelectronics processors, photovoltaic devices, and optoelectronics. The conventional methods of fabricating these structures often involve reactive-ion dry-etch processes utilizing ionized gases or wet chemical-based etching. Recently, the emergence of metal-assisted chemical etching (MacEtch) has showcased significant potential in enabling the creation of nanoscale features with exceptionally high aspect ratios. Nonetheless, the application of MacEtch to quaternary III-V and heteroepitaxial semiconductors remains relatively unexplored. This research introduces a novel approach named inverse-progression metal-assisted chemical etching (I-MacEtch) that centers around the utilization of a bimetallic catalyst, specifically focusing on the utilization of a bimetallic catalyst. This technique is employed to fabricate well-organized arrays of submicron pillars. The study elucidates that precise control over the vertical and lateral etch rate can be attained through the selection of a suitable metal adhesion layer, which improves the overall catalyst work function, thereby facilitating the streamlined fabrication of ordered arrays of InP submicron pillars possessing predefined aspect ratios.

A comprehensive analysis and simulation of two memristor-based neuromorphic architectures for nuclear radiation detection is presented. Both scalable architectures retrofit a locally competitive algorithm to solve overcomplete sparse approximation problems by harnessing memristor crossbar execution of vector–matrix multiplications. The proposed systems demonstrate excellent accuracy and throughput while consuming minimal energy for radionuclide detection. To ensure that the simulation results of our proposed hardware are realistic, the memristor parameters are chosen from our own fabricated memristor devices. Based on these results, we conclude that memristor-based computing is the preeminent technology for a radiation detection platform.

We present the fabrication of a MoS 2−x Se x thin film from a co-sputtering process using MoS 2 and MoSe 2 commercial targets with 99.9% purity. The sputtering of the MoS 2 and MoSe 2 was carried out using a straight and low-cost magnetron radio frequency sputtering recipe to achieve a MoS 2−x Se x phase with x = 1 and sharp interface formation as confirmed by Raman spectroscopy, time-of-flight secondary ion mass spectroscopy, and cross-sectional scanning electron microscopy. The sulfur and selenium atoms prefer to distribute randomly at the octahedral geometry of molybdenum inside the MoS 2−x Se x thin film, indicated by a blue shift in the A 1g and E 1 g vibrational modes at 355 cm −1 and 255 cm −1 , respectively. This work is complemented by computing the thermodynamic stability of a MoS 2−x Se x phase whereby density functional theory up to a maximum selenium concentration of 33.33 at.% in both a Janus-like and random distribution. Although the Janus-like and the random structures are in the same metastable state, the Janus-like structure is hindered by an energy barrier below selenium concentrations of 8 at.%. This research highlights the potential of transition metal dichalcogenides in mixed phases and the need for further exploration employing low-energy, large-scale methods to improve the materials’ fabrication and target latent applications of such structures.

Silicon nitride has long been employed in the microfabrication of thermal sensors due to its favorable material properties and the ease with which it facilitates surface micromachining. While a variety of studies have utilized thin silicon nitride membranes for high sensitivity thermal measurements, limited reports exist on the physical characteristics of membranes and platforms in a thickness limit much less than 100 nm. Herein, we report on the development of low-stress, suspended silicon nitride platform devices that enable thermal characterization of membranes ranging from 120 nm to less than 10 nm in thickness, providing thermal conductivities as low as 1.1 W m(-1 )K(-1 ) near room temperature. Applications of these platforms may enable appreciable enhancement in the performance of devices reliant upon environmental thermal isolation including bolometers, calorimeters, and gas sensors, among others.

A dry etching process to transfer the pattern of a photonic integrated circuit designfor high-speed laser communications is described. The laser stack under consideration is a3.2-mu m-thick InGaAs/InAlAs/InAlGaAs epitaxial structure grown by molecular beam epitaxy.The etching was performed using Cl2-based inductively-coupled-plasma and reactive-ion-etching(ICP-RIE) reactors. Four different recipes are presented in two similar ICP-RIE reactors, withspecial attention paid to the etched features formed with various hard mask compositions,in-situpassivations, and process temperatures. The results indicate that it is possible to producehigh-aspect-ratio features with sub-micron separation on this multilayer structure. Additionally,the results of the etching highlight the tradeoffs involved with the corresponding recipes. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Superconducting nanostripe single-photon detectors (SNSPDs) represent key components in silicon quantum photonic integrated circuits (SiQuPICs). They provide good timing precision, low dark counts, and high efficiency. The design, fabrication, and characterization of SiQuPICs comprising SNSPDs coupled to dielectric optical waveguides are the core objectives of our work. The detectors are positioned directly on the dielectric waveguide core to increase photon absorption by the superconducting nanostripes. We also present results on the SPICE circuit modeling of traveling-wave SNSPDs integrated with Si3N4/SiO2 optical waveguides.

Mechanical testing at small length scales has traditionally been resource-intensive due to difficulties with meticulous sample preparation, exacting load alignments, and precision measurements. Microscale fatigue testing can be particularly challenging due to the time-intensive, tedious repetition of single fatigue experiments. To mitigate these challenges, this work presents a new methodology for the high-throughput fatigue testing of thin films at the microscale. This methodology features a microelectromechanical systems-based Si carrier that can support the simultaneous and independent fatigue testing of an array of samples. To demonstrate this new technique, the microscale fatigue behavior of nanocrystalline Al is efficiently characterized via this Si carrier and automated fatigue testing with in situ scanning electron microscopy. This methodology reduces the total testing time by an order of magnitude, and the high-throughput fatigue results highlight the stochastic nature of the microscale fatigue response. This manuscript also discusses how this initial capability can be adapted to accommodate more samples, different materials, new geometries, and other loading modes.

We present the results of our investigations of molecular beam epitaxial growth of low-density quantum dots emitting in the telecommunication wavelength range (1.3 – 1.55 μm) based on InAs/InP and GaSb/GaAs materials systems. Our ultimate goal is to demonstrate single-photon emission from these quantum dots, using site-templating approach. © 2022 The Authors

Ultrathin absorber can improve specific detectivity and response time of microbolometers. We experimentally demonstrate an average absorptance of 48% +/- 2.5% in the 8-13 microns (769-1250 1/cm) spectral range in 10nm thick titanium nitride (TiN), a value bordering on the 50% fundamental absorptance limit for a suspended thin film. Such absorptance is close to the fundamental limit of 50% for free-standing ultrathin films.

The unique behavior of quantum systems, such as coherence, superposition, and entanglement, can be harnessed to process, encode, and transmit information. Each quantum application (communication, computing, metrology, sensing, etc.) places its own set of requirements on the underpinning photonic technology, but many of these requirements are common to all the applications, and they form the basis for the implementation of future silicon quantum photonic integrated circuits (SiQuPICs). These common elements include single- or entangled-pair photon sources, passive optics to coherently mix photonic modes, active optics and delay lines to reconfigure those modes, high extinction ratio filters, and single-photon detectors. In this paper, we describe the design and fabrication of a basic SiQuPIC, comprising single-photon or entangled-photon-pair sources coupled to passive optical waveguides ending with single-photon detectors, all integrated on a single Si chip.

The electronic structure and thermoelectric properties of MoX 2 (X = S, Se) Van der Waals heterojunctions are reported, with the intention of motivating the design of electronic devices using such materials. Calculations indicate the proposed heterojunctions are thermodynamically stable and present a band gap reduction from 1.8 eV to 0.8 eV. The latter effect is highly related to interactions between metallic d‐character orbitals and chalcogen p‐character orbitals. The theoretical approach allows to predict a transition from semiconducting to semi‐metallic behavior. The band alignment indicates a type‐I heterojunction and band offsets of 0.2 eV. Transport properties show clear n‐type nature and a high Seebeck coefficient at 300 K, along with conductivity values (σ/τ) in the order of 10 20 . Lastly, using the Landauer approach and ballistic transport, the proposed heterojunctions can be modeled as a channel material for a typical one‐gate transistor configuration predicting subthreshold values of ≈60 mV dec −1 and field–effect mobilities of ≈160 cm −2 V −1 s −1 .

Microbolometers with ultrathin and efficient absorber can improve specific detectivity and response time. Resonance enhanced absorber increases thermal mass and hence reduces response time. However, for an ultrathin film to absorb light efficiently, the dielectric function of the film and its thickness must satisfy strict requirements. We experimentally demonstrate an average absorptance of 48% +/-2.5% in the 8–13 microns (769–1250 cm-1) spectral range for 10nm thick titanium nitride (TiN) supported by 100nm thick SiN suspended membrane, a value bordering on the fundamental absorptance limit of 50%.

Tungsten trioxide (WO3) is a versatile n-type semiconductor with outstanding chromogenic properties highly used to fabricate sensors and electrochromic devices. We present a comprehensive experimental study related to piezoresponse with piezoelectric coefficient d33 = 35 pmV−1 on WO3 thin films ~200 nm deposited using RF-sputtering onto alumina (Al2O3) substrate with post-deposit annealing treatment of 400 °C in a 3% H2/N2-forming gas environment. X-ray diffraction (XRD) confirms a mixture of orthorhombic and tetragonal phases of WO3 with domains with different polarization orientations and hysteresis behavior as observed by piezoresponse force microscopy (PFM). Furthermore, using atom probe tomography (APT), the microstructure reveals the formation of N2-filled nanovoids that acts as strain centers producing a local deformation of the WO3 lattice into a non-centrosymmetric structure, which is related to piezoresponse observations.