Probing Non-Equilibrium Pair-Breaking and Quasiparticle Dynamics in Nb Superconducting Resonators Under Magnetic Fields.

We conducted a comprehensive study of the non-equilibrium dynamics of Cooper pair breaking, quasiparticle (QP) generation, and relaxation in niobium (Nb) cut from superconducting radio-frequency (SRF) cavities, as well as various Nb resonator films from transmon qubits. Using ultrafast pump-probe spectroscopy, we were able to isolate the superconducting coherence and pair-breaking responses. Our results reveal both similarities and notable differences in the temperature- and magnetic-field-dependent dynamics of the SRF cavity and thin-film resonator samples.

Structure and Formation Mechanisms in Tantalum and Niobium Oxides in Superconducting Quantum Circuits.

Improving the qubit's lifetime (T) is crucial for fault-tolerant quantum computing. Recent advancements have shown that replacing niobium (Nb) with tantalum (Ta) as the base metal significantly increases T, likely due to a less lossy native surface oxide. However, understanding the formation mechanism and nature of both surface oxides is still limited.

Recent Development of Halide Perovskite Materials and Devices for Ionizing Radiation Detection.

Ionizing radiation such as X-rays and γ-rays has been extensively studied and used in various fields such as medical imaging, radiographic nondestructive testing, nuclear defense, homeland security, and scientific research. Therefore, the detection of such high-energy radiation with high-sensitivity and low-cost-based materials and devices is highly important and desirable. Halide perovskites have emerged as promising candidates for radiation detection due to the large light absorption coefficient, large resistivity, low leakage current, high mobility, and simplicity in synthesis and processing as compared with commercial silicon (Si) and amorphous selenium (-Se).

Developing a Chemical and Structural Understanding of the Surface Oxide in a Niobium Superconducting Qubit.

Superconducting thin films of niobium have been extensively employed in transmon qubit architectures. Although these architectures have demonstrated improvements in recent years, further improvements in performance through materials engineering will aid in large-scale deployment. Here, we use information retrieved from secondary ion mass spectrometry and electron microscopy to conduct a detailed assessment of the surface oxide that forms in ambient conditions for transmon test qubit devices patterned from a niobium film.

Direct Patterning of Optoelectronic Nanostructures Using Encapsulated Layered Transition Metal Dichalcogenides.

Direct top-down nanopatterning of semiconductors is a powerful tool for engineering properties of optoelectronic devices. Translating this approach to two-dimensional semiconductors such as monolayer transition metal dichalcogenides (TMDs) is challenging because of both the small scales required for confinement and the degradation of electronic and optical properties caused by high-energy and high-dose electron radiation used for high-resolution top-down direct electron beam patterning. We show that encapsulating a TMD monolayer with hexagonal boron nitride preserves the narrow exciton linewidths and emission intensity typical in such heterostructures after electron beam lithography, allowing direct patterning of functional optical monolayer nanostructures on scales of a few tens of nanometers.

Making the Most of your Electrons: Challenges and Opportunities in Characterizing Hybrid Interfaces with STEM.

Inspired by the unique architectures composed of hard and soft materials in natural and biological systems, synthetic hybrid structures and associated soft-hard interfaces have recently evoked significant interest. Soft matter is typically dominated by fluctuations even at room temperature, while hard matter (which often serves as the substrate or anchor for the soft component) is governed by rigid mechanical behavior. This dichotomy offers considerable opportunities to leverage the disparate properties offered by these components across a wide spectrum spanning from basic science to engineering insights with significant technological overtones.

Mechanistic Investigation of Molybdenum Disulfide Defect Photoluminescence Quenching by Adsorbed Metallophthalocyanines.

Lattice defects play an important role in determining the optical and electrical properties of monolayer semiconductors such as MoS. Although the structures of various defects in monolayer MoS are well studied, little is known about the nature of the fluorescent defect species and their interaction with molecular adsorbates. In this study, the quenching of the low-temperature defect photoluminescence (PL) in MoS is investigated following the deposition of metallophthalocyanines (MPcs).

Tuning of Optical Phonons in α-MoO-VO Multilayers.

Merging the properties of VO and van der Waals (vdW) materials has given rise to novel tunable photonic devices. Despite recent studies on the effect of the phase change of VO on tuning near-field optical response of phonon polaritons in the infrared range, active tuning of optical phonons (OPhs) using far-field techniques has been scarce. Here, we investigate the tunability of OPhs of α-MoO in a multilayer structure with VO.

Spatial Mapping of Electrostatic Fields in 2D Heterostructures.

electron microscopy is an effective tool for understanding the mechanisms driving novel phenomena in 2D structures. However, due to practical challenges, it is difficult to address these technologically relevant 2D heterostructures with electron microscopy. Here, we use the differential phase contrast (DPC) imaging technique to build a methodology for probing local electrostatic fields during electrical operation with nanoscale spatial resolution in such materials.

Valley-selective optical Stark effect of exciton-polaritons in a monolayer semiconductor.

Selective breaking of degenerate energy levels is a well-known tool for coherent manipulation of spin states. Though most simply achieved with magnetic fields, polarization-sensitive optical methods provide high-speed alternatives. Exploiting the optical selection rules of transition metal dichalcogenide monolayers, the optical Stark effect allows for ultrafast manipulation of valley-coherent excitons.

Correction: Topology of transition metal dichalcogenides: the case of the core-shell architecture.

Correction for 'Topology of transition metal dichalcogenides: the case of the core-shell architecture' by Jennifer G. DiStefano et al., Nanoscale, 2020, 12, 23897-23919, DOI: 10.

Topology of transition metal dichalcogenides: the case of the core-shell architecture.

Non-planar architectures of the traditionally flat 2D materials are emerging as an intriguing paradigm to realize nascent properties within the family of transition metal dichalcogenides (TMDs). These non-planar forms encompass a diversity of curvatures, morphologies, and overall 3D architectures that exhibit unusual characteristics across the hierarchy of length-scales. Topology offers an integrated and unified approach to describe, harness, and eventually tailor non-planar architectures through both local and higher order geometry.

Lithography-free IR polarization converters via orthogonal in-plane phonons in α-MoO flakes.

Exploiting polaritons in natural vdW materials has been successful in achieving extreme light confinement and low-loss optical devices and enabling simplified device integration. Recently, α-MoO has been reported as a semiconducting biaxial vdW material capable of sustaining naturally orthogonal in-plane phonon polariton modes in IR. In this study, we investigate the polarization-dependent optical characteristics of cavities formed using α-MoO to extend the degrees of freedom in the design of IR photonic components exploiting the in-plane anisotropy of this material.

Direct Visualization of Electric-Field-Induced Structural Dynamics in Monolayer Transition Metal Dichalcogenides.

Layered transition metal dichalcogenides offer many attractive features for next-generation low-dimensional device geometries. Due to the practical and fabrication challenges related to methods, the atomistic dynamics that give rise to realizable macroscopic device properties are often unclear. In this study, transmission electron microscopy techniques are utilized in order to understand the structural dynamics at play, especially at interfaces and defects, in the prototypical film of monolayer MoS under electrical bias.

Spatial Mapping of Hot-Spots at Lateral Heterogeneities in Monolayer Transition Metal Dichalcogenides.

Lateral heterogeneities in atomically thin 2D materials such as in-plane heterojunctions and grain boundaries (GBs) provide an extrinsic knob for manipulating the properties of nano- and optoelectronic devices and harvesting novel functionalities. However, these heterogeneities have the potential to adversely affect the performance and reliability of the 2D devices through the formation of nanoscopic hot-spots. In this report, scanning thermal microscopy (SThM) is utilized to map the spatial distribution of the temperature rise within monolayer transition metal dichalcogenide (TMD) devices upon dissipating a high electrical power through a lateral interface.

Morphological Engineering of Winged Au@MoS Heterostructures for Electrocatalytic Hydrogen Evolution.

Molybdenum disulfide (MoS) has been recognized as a promising cost-effective catalyst for water-splitting hydrogen production. However, the desired performance of MoS is often limited by insufficient edge-terminated active sites, poor electrical conductivity, and inefficient contact to the supporting substrate. To address these limitations, we developed a unique nanoarchitecture (namely, winged Au@MoS heterostructures enabled by our discovery of the "seeding effect" of Au nanoparticles for the chemical vapor deposition synthesis of vertically aligned few-layer MoS wings).

Site-Specific Positioning and Patterning of MoS Monolayers: The Role of Au Seeding.

Monolayers of transition metal dichalcogenides (TMDs) are attractive for various modern semiconductor devices. However, the limited control over the location, yield, and size distribution of the products using current synthesis methods has severely limited their large-scale applicability. Herein, we identify the ability to use metal ( e.

Intrinsic Transport in 2D Heterostructures Mediated through h-BN Tunneling Contacts.

Understanding the electronic transport of monolayer transition metal dichalcogenides (TMDs) and their heterostructures is complicated by the difficulty in achieving electrical contacts that do not perturb the material. Typically, metal deposition on monolayer TMDs leads to hybridization between the TMD and the metal, which produces Schottky barriers at the metal/semiconductor interface. In this work, we apply the recently reported hexagonal boron nitride (h-BN) tunnel contact scheme to probe the junction characteristics of a lateral TMD heterostructure grown via chemical vapor deposition.

Optically Active 1D MoS Nanobelts.

Transition metal dichalcogenides can be synthesized in a wide range of structures. 1D geometries, including nanotubes and nanowires, are especially intriguing due to enhanced light-matter interactions stemming from both the thickness and width possessing subwavelength dimensions. In this letter, we demonstrate the synthesis of 1D MoS nanobelts through chemical vapor deposition and examine the mechanism driving the formation of this material.

Superior Plasmonic Photodetectors Based on Au@MoS Core-Shell Heterostructures.

Integrating plasmonic materials into semiconductor media provides a promising approach for applications such as photosensing and solar energy conversion. The resulting structures introduce enhanced light-matter interactions, additional charge trap states, and efficient charge-transfer pathways for light-harvesting devices, especially when an intimate interface is built between the plasmonic nanostructure and semiconductor. Herein, we report the development of plasmonic photodetectors using Au@MoS heterostructures-an Au nanoparticle core that is encapsulated by a CVD-grown multilayer MoS shell, which perfectly realizes the intimate and direct interfacing of Au and MoS.

Au@MoS Core-Shell Heterostructures with Strong Light-Matter Interactions.

There are emerging opportunities to harness diverse and complex geometric architectures based on nominal two-dimensional atomically layered structures. Herein we report synthesis and properties of a new core-shell heterostructure, termed Au@MoS, where the Au nanoparticle is snugly and contiguously encapsulated by few shells of MoS atomic layers. The heterostructures were synthesized by direct growth of multilayer fullerene-like MoS shell on Au nanoparticle cores.