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Carrier and phonon dynamics in a multilayer WSe2 film are captured by extreme ultraviolet (XUV) transient absorption (TA) spectroscopy at the W N6,7, W O2,3, and Se M4,5 edges (30-60 eV). After the broadband optical pump pulse, the XUV probe directly reports on occupations of optically excited holes and phonon-induced band renormalizations. When compared with density functional theory calculations, XUV transient absorption due to holes is identified below the W O3 edge whereas signals at the Se M4,5 edges are dominated by phonon dynamics. Therein, 0.4 ps hole relaxation time, 1.5 ps carrier recombination time, and 1.7 ps phonon heating time are extracted. The acquisition of hole and phonon-induced signals in a single experiment can facilitate the investigation of the correlations between electron and phonon dynamics. Furthermore, the simultaneous observation of signals from different elements can be further extended to explore photochemical processes in multilayers and alloys, thereby providing key information for their applications in electronics, photocatalysts, and spintronics.

Surface plasmons have found a wide range of applications in plasmonic and nanophotonic devices. The combination of plasmonics with three-dimensional photonic crystals has enormous potential for the efficient localization of light in high surface area photoelectrodes. However, the metals traditionally used for plasmonics are difficult to form into three-dimensional periodic structures and have limited optical penetration depth at operational frequencies, which limits their use in nanofabricated photonic crystal devices. The recent decade has seen an expansion of the plasmonic material portfolio into conducting ceramics, driven by their potential for improved stability, and their conformal growth via atomic layer deposition has been established. In this work, we have created three-dimensional photonic crystals with an ultrathin plasmonic titanium nitride coating that preserves photonic activity. Plasmonic titanium nitride enhances optical fields within the photonic electrode while maintaining sufficient light penetration. Additionally, we show that post-growth annealing can tune the plasmonic resonance of titanium nitride to overlap with the photonic resonance, potentially enabling coupled-phenomena applications for these three-dimensional nanophotonic systems. Through characterization of the tuning knobs of bead size, deposition temperature and cycle count, and annealing conditions, we can create an electrically- and plasmonically-active photonic crystal as-desired for a particular application of choice.

Two-dimensional (2D) excitons arise from electron-hole confinement along one spatial dimension. Such excitations are often described in terms of Frenkel or Wannier limits according to the degree of exciton spatial localization and the surrounding dielectric environment. In hybrid material systems, such as the 2D perovskites, the complex underlying interactions lead to excitons of an intermediate nature, whose description lies somewhere between the two limits, and a better physical description is needed. Here, we explore the photophysics of a tuneable materials platform where covalently bonded metal-chalcogenide layers are spaced by organic ligands that provide confinement barriers for charge carriers in the inorganic layer. We consider self-assembled, layered bulk silver benzeneselenolate, [AgSePh]∞, and use a combination of transient absorption spectroscopy and ab initio GW plus Bethe-Salpeter equation calculations. We demonstrate that in this non-polar dielectric environment, strongly anisotropic excitons dominate the optical transitions of [AgSePh]∞. We find that the transient absorption measurements at room temperature can be understood in terms of low-lying excitons confined to the AgSe planes with in-plane anisotropy, featuring anisotropic absorption and emission. Finally, we present a pathway to control the exciton behaviour by changing the chalcogen in the material lattice. Our studies unveil unexpected excitonic anisotropies in an unexplored class of tuneable, yet air-stable, hybrid quantum wells, offering design principles for the engineering of an ordered, yet complex dielectric environment and its effect on the excitonic phenomena in such emerging materials.

Transition metal dichalcogenides (TMDs) promise to revolutionize optoelectronic applications. While monolayer exfoliation and vapor phase growth produce extremely high quality 2D materials, direct fabrication at wafer scale remains a significant challenge. Here, we present a method that we call ‘lateral conversion’, which enables the synthesis of patterned TMD structures, with control over the thickness down to a few layers, at lithographically predefined locations. In this method, chemical conversion of a metal-oxide film to TMD layers proceeds by diffusion of precursor propagating laterally between silica layers, resulting in structures where delicate chalcogenide films are protected from contamination or oxidation. Lithographically patterned WS2 structures were synthesized by lateral conversion and analyzed in detail by hyperspectral Raman imaging, scanning electron microscopy and transmission electron microscopy. The rate of conversion was investigated as a function of time, temperature, and thickness of the converted film. In addition, the process was extended to grow patterned MoS2, WSe2, MoSe2 structures, and to demonstrate unique WS2/SiO2 multilayer structures. We believe this method will be applicable to a variety of additional chalcogenide materials, and enable their incorporation into novel architectures and devices.

Control of impurity concentrations in semiconducting materials is essential to device technology. Because of their intrinsic confinement, the properties of two-dimensional semiconductors such as transition metal dichalcogenides (TMDs) are more sensitive to defects than traditional bulk materials. The technological adoption of TMDs is dependent on the mitigation of deleterious defects and guided incorporation of functional foreign atoms. The first step toward impurity control is the identification of defects and assessment of their electronic properties. Here, we present a comprehensive study of point defects in monolayer tungsten disulfide (WS2) grown by chemical vapor deposition using scanning tunneling microscopy/spectroscopy, CO-tip noncontact atomic force microscopy, Kelvin probe force spectroscopy, density functional theory, and tight-binding calculations. We observe four different substitutional defects: chromium (CrW) and molybdenum (MoW) at a tungsten site, oxygen at sulfur sites in both top and bottom layers (OS top/bottom), and two negatively charged defects (CD type I and CD type II). Their electronic fingerprints unambiguously corroborate the defect assignment and reveal the presence or absence of in-gap defect states. CrW forms three deep unoccupied defect states, two of which arise from spin-orbit splitting. The formation of such localized trap states for CrW differs from the MoW case and can be explained by their different d shell energetics and local strain, which we directly measured. Utilizing a tight-binding model the electronic spectra of the isolectronic substitutions OS and CrW are mimicked in the limit of a zero hopping term and infinite on-site energy at a S and W site, respectively. The abundant CDs are negatively charged, which leads to a significant band bending around the defect and a local increase of the contact potential difference. In addition, CD-rich domains larger than 100 nm are observed, causing a work function increase of 1.1 V. While most defects are electronically isolated, we also observed hybrid states formed between CrW dimers. The important role of charge localization, spin-orbit coupling, and strain for the formation of deep defect states observed at substitutional defects in WS2 as reported here will guide future efforts of targeted defect engineering and doping of TMDs.

Structural defects in 2D materials offer an effective way to engineer new material functionalities beyond conventional doping. We report on the direct experimental correlation of the atomic and electronic structure of a sulfur vacancy in monolayer WS_{2} by a combination of CO-tip noncontact atomic force microscopy and scanning tunneling microscopy. Sulfur vacancies, which are absent in as-grown samples, were deliberately created by annealing in vacuum. Two energetically narrow unoccupied defect states followed by vibronic sidebands provide a unique fingerprint of this defect. Direct imaging of the defect orbitals, together with ab initio GW calculations, reveal that the large splitting of 252±4  meV between these defect states is induced by spin-orbit coupling.

Two-dimensional materials with engineered composition and structure will provide designer materials beyond conventional semiconductors. However, the potentials of defect engineering remain largely untapped, because it hinges on a precise understanding of electronic structure and excitonic properties, which are not yet predictable by theory alone. Here, we utilize correlative, nanoscale photoemission spectroscopy to visualize how local introduction of defects modifies electronic and excitonic properties of two-dimensional materials at the nanoscale. As a model system, we study chemical vapor deposition grown monolayer WS2, a prototypical, direct gap, two-dimensional semiconductor. By cross-correlating nanoscale angle-resolved photoemission spectroscopy, core level spectroscopy, and photoluminescence, we unravel how local variations in defect density influence electronic structure, lateral band alignment, and excitonic phenomena in synthetic WS2 monolayers.

Materials for nanophotonic devices ideally combine ease of deposition, very high refractive index, and facile pattern formation through lithographic templating and/or etching. In this work, we present a scalable method for producing high refractive index WS2 layers by chemical conversion of WO3 synthesized via atomic layer deposition (ALD). These conformal nanocrystalline thin films demonstrate a surprisingly high index of refraction (n > 3.9), and structural fidelity compatible with lithographically defined features down to ~10 nm. Although this process yields highly polycrystalline films, the optical constants are in agreement with those reported for single crystal bulk WS2. Subsequently, we demonstrate three photonic structures - first, a two-dimensional hole array made possible by patterning and etching an ALD WO3 thin film before conversion, second, an analogue of the 2D hole array first patterned into fused silica before conformal coating and conversion, and third, a three-dimensional inverse opal photonic crystal made by conformal coating of a self-assembled polystyrene bead template. These results can be trivially extended to other transition metal dichalcogenides, thus opening new opportunities for photonic devices based on high refractive index materials.

Due to its high refractive index and low absorption coefficient, gallium phosphide is an ideal material for photonic structures targeted at the visible wavelengths. However, these properties are only realized with high quality epitaxial growth, which limits substrate choice and thus possible photonic applications. In this work, we report the fabrication of single crystal gallium phosphide thin films on transparent glass substrates via transfer bonding. GaP thin films on Si (001) and (112) grown by MOCVD are bonded to glass, and then the growth substrate is removed with a XeF2 vapor etch. The resulting GaP films have surface roughnesses below 1 nm RMS and exhibit room temperature band edge photoluminescence. Magnesium doping yielded p-type films with a carrier density of 1.6 × 1017 cm-3 that exhibited mobilities as high as 16 cm2V-1s-1. Due to their unique optical properties, these films hold much promise for use in advanced optical devices.

2D transition metal dichalcogenides (TMDs) are commonly grown by chemical vapor deposition using transition metal oxides as solid precursors. Despite the widespread use of this technique, challenges in reproducibility, coverage, and material quality are pervasive, suggestive of unknown and uncontrolled process parameters. In this communication, we demonstrate the impact of water vapor on this growth process. Our results show a direct correlation between gas phase water content and the morphology of TMD films. In particular, we show that the presence of water enhances volatilization, and therefore the vapor transport of tungsten and molybdenum oxide. Surprisingly, we find that water not only plays an important role in volatilization but is also compatible with TMD growth. In fact, carefully controlled humidity can consistently produce high quality, luminescent materials.

Purpose: In preclinical models, glucocorticoid receptor (GR) signaling drives resistance to taxane chemotherapy in multiple solid tumors via upregulation of antiapoptotic pathways. ORIC-101 is a potent and selective GR antagonist that was investigated in combination with taxane chemotherapy as an anticancer regimen preclinically and in a phase 1 clinical trial., Patients and Methods: The ability of ORIC-101 to reverse taxane resistance was assessed in cell lines and xenograft models, and a phase 1 study (NCT03928314) was conducted in patients with advanced solid tumors to determine the dose, safety, and antitumor activity of ORIC-101 with nab-paclitaxel., Results: ORIC-101 reversed chemoprotection induced by glucocorticoids in vitro and achieved tumor regressions when combined with paclitaxel in both taxane-naïve and -resistant xenograft models. In the phase 1 study, 21 patients were treated in dose escalation and 62 patients were treated in dose expansion. All patients in dose expansion had previously progressed on a taxane-based regimen. In dose escalation, five objective responses were observed. A preplanned futility analysis in dose expansion showed a 3.2% (95% confidence interval, 0.4-11.2) objective response rate with a median progression-free survival of 2 months (95% confidence interval, 1.8-2.8) across all four cohorts, leading to study termination. Pharmacodynamic analysis of tissue and plasma showed GR pathway downregulation in most patients in cycle 1., Conclusions: ORIC-101 with nab-paclitaxel showed limited clinical activity in taxane-resistant solid tumors. Despite clear inhibition of GR pathway signaling, the insufficient clinical signal underscores the challenges of targeting a single resistance pathway when multiple mechanisms of resistance may be in play., Significance: Glucocorticoid receptor (GR) upregulation is a mechanism of resistance to taxane chemotherapy in preclinical cancer models. ORIC-101 is a small molecule GR inhibitor. In this phase 1 study, ORIC-101 plus nab-paclitaxel did not show meaningful clinical benefit in patients who previously progressed on taxanes despite successful GR pathway downregulation., (©2024 The Authors; Published by the American Association for Cancer Research.)

Background: Walk-in clinics are growing in popularity around the world as a substitute for traditional medical care delivered in physician offices and emergency rooms, but their clinical efficacy is unclear., Objectives: To assess the quality of care and patient satisfaction of walk-in clinics compared to that of traditional physician offices and emergency rooms for people who present with basic medical complaints for either acute or chronic issues., Search Methods: We searched CENTRAL, MEDLINE, Embase, six other databases, and two trials registers on 22 March 2016 together with reference checking, citation searching, and contact with study authors to identify additional studies. We applied no restrictions on language, publication type, or publication year., Selection Criteria: Study design: randomized trials, non-randomized trials, and controlled before-after studies., Population: standalone physical clinics not requiring advance appointments or registration, that provided basic medical care without expectation of follow-up. Comparisons: traditional primary care practices or emergency rooms., Data Collection and Analysis: We used standard methodological procedures expected by Cochrane and the Cochrane Effective Practice and Organisation of Care (EPOC) Group., Main Results: The literature search identified 6587 citations, of which we considered 65 to be potentially relevant. We reviewed the abstracts of all 65 potentially relevant studies and retrieved the full texts of 12 articles thought to fit our study criteria. However, following independent author assessment of the full texts, we excluded all 12 articles., Authors' Conclusions: Controlled trial evidence about the mortality, morbidity, quality of care, and patient satisfaction of walk-in clinics is currently not available.