Историко-педагогический обзор детской беспризорности в Древней Руси и императорской России

Axially resolved microphotoluminescence mapping of semiconductor nanowires held in an optical tweezers reveals important new experimental information regarding equilibrium trapping points and trapping stability of high aspect ratio nanostructures. In this study, holographic optical tweezers are used to scan trapped InP nanowires along the beam direction with respect to a fixed excitation source and the luminescent properties are recorded. It is observed that nanowires with lengths on the range of 3–15 μm are stably trapped near the tip of the wire with the long segment positioned below the focus in an inverted trapping configuration. Through the use of trap multiplexing we investigate the possibility of improving the axial stability of the trapped nanowires. Our results have important implication for applications of optically assisted nanowire assembly and optical tweezers based scanning probes microscopy

Automated Computer Vision-Enabled Manufacturing of Nanowire Devices.

We present a high-throughput method for identifying and characterizing individual nanowires and for automatically designing electrode patterns with high alignment accuracy. Central to our method is an optimized machine-readable, lithographically processable, and multi-scale fiducial marker system─dubbed LithoTag─which provides nanostructure position determination at the nanometer scale. A grid of uniquely defined LithoTag markers patterned across a substrate enables image alignment and mapping in 100% of a set of >9000 scanning electron microscopy (SEM) images (>7 gigapixels). Combining this automated SEM imaging with a computer vision algorithm yields location and property data for individual nanowires. Starting with a random arrangement of individual InAs nanowires with diameters of 30 ± 5 nm on a single chip, we automatically design and fabricate >200 single-nanowire devices. For >75% of devices, the positioning accuracy of the fabricated electrodes is within 2 pixels of the original microscopy image resolution. The presented LithoTag method enables automation of nanodevice processing and is agnostic to microscopy modality and nanostructure type. Such high-throughput experimental methodology coupled with data-extensive science can help overcome the characterization bottleneck and improve the yield of nanodevice fabrication, driving the development and applications of nanostructured materials

III–V Thin Films for Flexible, Cost-Effective, and Emerging Applications in Optoelectronics and Photonics

ConspectusSemiconductor thin films possess a unique set of characteristics, making them highly suitable for a number of optoelectronic and photonic applications. The III–V semiconductors, in particular, are lightweight, flexible, durable, and suitable for high-efficiency devices. For example, flexible and lightweight III–V thin-film solar cells have been demonstrated with a solar conversion efficiency of 37.8%. Besides photovoltaics, III–V semiconductor thin films are also suitable for LEDs, lasers, detectors, sensors, and frequency-converting devices. These characteristics make the III–V thin films excellent candidates for applications in space, Internet of things, drones, autonomous vehicles, and wearable devices.Despite these advantages, the high cost of fabrication has hindered the uptake of III–V thin films. On the other hand, recent developments in multilayer epitaxial lift off (MELO) may drastically improve the cost-efficiency of device fabrication. These developments are discussed in the Account, and they alone may improve cost-efficiency by a factor of 4. Even further cost improvements may be achieved with the use of ultrathin solar cells. For ultrathin cells, a promising architecture is discussed, where an epitaxially grown III–V absorber layer is sandwiched between nonepitaxial carrier-selective contact layers thus forming a double-heterojunction. This structure minimizes epitaxial thickness and promises low-cost and high-efficiency devices, with theoretical cost-efficiency improvement reaching as high as a factor of 10 when combined with MELO.Perhaps even more interestingly, recent developments in III–V thin films demonstrate a wholly novel device types. One interesting device architecture uses single-crystalline nanofilms with a thickness of only tens of nanometers, thereby reducing device cost significantly. These ultralow thicknesses have two consequences: the surface properties become dominant, and the optical properties, such as absorption, are decoupled from bulk material values. This Account discusses an example of UV-sensitive GaAs photodetectors, contrasting typical GaAs devices that are sensitive in infrared.Another important device class that has attracted significant attention recently is metamaterials. Metamaterial-based devices offer novel solutions to a whole range of applications in photonics and optics. They are planar structures with nanoscale resonators that are used to focus, bend, and modify light. III–V thin films are excellent candidates for metamaterial fabrication due to their high refractive indices, high nonlinear-optical coefficients, and direct band gaps that allow the fabrication of optoelectronic metamaterials. III–V metamaterials with a focus on frequency conversion are discussed.As a whole, this Account discusses various facets of III–V thin-film technology, from cost-efficient fabrication to novel and emerging device types. The improved cost-efficiency makes them attractive for a number of increasingly important application areas where lightweight, flexibility, and high performance are critical. Simultaneously, the novel device types open new avenues for the use of III–V thin films. Nanofilm devices can be ultralow cost and offer an interesting platform for applications in sensing and detection. Metamaterials on the other hand, are versatile photonic devices that are thought to play a key role in the fourth industrial revolution. These aspects suggest that III–V thin films will attract significantly increasing interest in the near future in research of novel devices as well as in many real-world applications

Characteristics and Thermal Control of Random and Fabry–Pérot Lasing in Nanowire Arrays

Nanolasers have attracted intense interest in the past decade because they are more compact, can be operated at higher modulation speed, and are more power-efficient than classical lasers. Thanks to these capabilities, nanolasers are now emerging for a variety of practical applications. This work presents hybrid nanolasers supporting both Fabry–Pérot and random lasing modes at room and cryogenic temperatures. These lasing modes are shown to exhibit differences in their lasing properties, such as wavelength, polarization, and coherency. New practical and broadly applicable methods are presented to distinguish these modes, including polarization-resolved measurements, near-field imaging, and photoluminescence spectroscopy measurements. Importantly, this paper demonstrates tuning between different lasing types in nanolasers, i.e., between Fabry–Pérot and random lasing. This allows the tuning of several lasing properties beyond only wavelength tuning. Thermal tuning is used here, where the Fabry–Pérot lasing modes are dominant at cryogenic temperatures, and at room temperature, random lasing becomes dominant. This work presents the first NW dual-cavity nanolaser and the first demonstration of thermal tuning between laser cavity types. As such, it provides the foundation for hybrid nanolasers, where various lasing properties can be tuned

Strain-Engineered Multilayer Epitaxial Lift-Off for Cost-Efficient III–V Photovoltaics and Optoelectronics

The efficient removal of epitaxially grown materials from their host substrate has a pivotal role in reducing the cost and material consumption of III–V solar cells and in making flexible thin-film devices. A multilayer epitaxial lift-off process is demonstrated that is scalable in both film size and in the number of released films. The process utilizes in-built, individually engineered epitaxial strain in each film to tailor the bending without the need for external layers to induce strain. Even without external support layers, the films retain good integrity after the lift-off, as evidenced by photoluminescence measurements. The films can be further processed into devices, demonstrated here with the fabrication of cm-scale solar cells using a three-layer lift-off process. Based on the included cost analysis, the solar cells are fabricated with a facile two-step process from the as-released films. The scalable multilayer lift-off process is highly cost-efficient and enables a 4-to-6-fold reduction in the cost with respect to the single-layer epitaxial lift-off process. The results are therefore significant for III–V photovoltaics and any other technologies that rely on thin-film III–V semiconductors

Strain-Engineered Multilayer Epitaxial Lift-Off for Cost-Efficient III–V Photovoltaics and Optoelectronics

The efficient removal of epitaxially grown materials from their host substrate has a pivotal role in reducing the cost and material consumption of III–V solar cells and in making flexible thin-film devices. A multilayer epitaxial lift-off process is demonstrated that is scalable in both film size and in the number of released films. The process utilizes in-built, individually engineered epitaxial strain in each film to tailor the bending without the need for external layers to induce strain. Even without external support layers, the films retain good integrity after the lift-off, as evidenced by photoluminescence measurements. The films can be further processed into devices, demonstrated here with the fabrication of cm-scale solar cells using a three-layer lift-off process. Based on the included cost analysis, the solar cells are fabricated with a facile two-step process from the as-released films. The scalable multilayer lift-off process is highly cost-efficient and enables a 4-to-6-fold reduction in the cost with respect to the single-layer epitaxial lift-off process. The results are therefore significant for III–V photovoltaics and any other technologies that rely on thin-film III–V semiconductors

Surface-Tailored InP Nanowires via Self-Assembled Au Nanodots for Efficient and Stable Photoelectrochemical Hydrogen Evolution

With a band gap close to the Shockley–Quiesser limit and excellent conduction band alignment with the water reduction potential, InP is an ideal photocathode material for photoelectrochemical (PEC) water reduction. Here, we develop facile self-assembled Au nanodots based on dewetting phenomena as a masking technique to fabricate wafer-scale InP nanowires (NWs) via a top-down approach. In addition, we report dual-function wet treatment using sulfur-dissolved oleylamine (S-OA) to remove a plasma-damaged surface in a controlled manner and stabilize InP NWs against surface corrosion in harsh electrolyte solutions. The resulting InP NW photocathodes exhibit an excellent photocurrent density of 33 mA/cm2 under 1 sun illumination in 1 M HCl with a highly stabilized performance without needing additional protection layers. Our approach combining large-area NW fabrication and surface engineering synergistically enhances light harvesting and PEC performance and stability, thereby providing a pathway for the development of efficient and durable InP photoelectrodes in a scalable manner

Understanding the Effect of Catalyst Size on the Epitaxial Growth of Hierarchical Structured InGaP Nanowires

Understanding the effect of a catalyst on the growth of nanowires is crucial for their controllable synthesis. In this study, we report the growth of InGaP nanowires induced by different-sized Au catalysts by metal–organic chemical vapor deposition. Through electron microscopy characterization, two types of InGaP nanowires are identified, and the difference in catalyst size is shown to cause their different morphological, structural, and compositional characteristics. Furthermore, the influencing mechanism of catalyst size on the formation of hierarchical structures in nanowires is discussed. This study provides an insight for a better understanding of the growth of ternary nanowires, especially the effect of catalyst size, which can be a promising approach to control the ternary nanowire growth, and is therefore beneficial for the design of the corresponding nanowire-based device

Self-powered InP Nanowire Photodetector for Single Photon Level Detection at Room Temperature

Highly sensitive photodetectors with single photon level detection is one of the key components to a range of emerging technologies, in particular the ever-growing field of optical communication, remote sensing, and quantum computing. Currently, most of the single-photon detection technologies require external biasing at high voltages and/or cooling to low temperatures, posing great limitations for wider applications. Here, we demonstrate InP nanowire array photodetectors that can achieve single-photon level light detection at room temperature without an external bias. We use top-down etched, heavily doped p-type InP nanowires and n-type AZO/ZnO carrier selective contact to form a radial p-n junction with a built-in electric field exceeding 3x10^5 V/cm at 0 V. The device exhibits broadband light sensitivity and can distinguish a single photon per pulse from the dark noise at 0 V, enabled by its design to realize near-ideal broadband absorption, extremely low dark current, and highly efficient charge carrier separation. Meanwhile, the bandwidth of the device reaches above 600 MHz with a timing jitter of 538 ps. The proposed device design provides a new pathway towards low-cost, high-sensitivity, self-powered photodetectors for numerous future applications