Broadband Linear-Dichroic Photodetector in a Black Phosphorus Vertical p-n Junction

The ability to detect light over a broad spectral range is central for practical optoelectronic applications, and has been successfully demonstrated with photodetectors of two-dimensional layered crystals such as graphene and MoS2. However, polarization sensitivity within such a photodetector remains elusive. Here we demonstrate a linear-dichroic broadband photodetector with layered black phosphorus transistors, using the strong intrinsic linear dichroism arising from the in-plane optical anisotropy with respect to the atom-buckled direction, which is polarization sensitive over a broad bandwidth from 400 nm to 3750 nm. Especially, a perpendicular build-in electric field induced by gating in black phosphorus transistors can spatially separate the photo-generated electrons and holes in the channel, effectively reducing their recombination rate, and thus enhancing the efficiency and performance for linear dichroism photodetection. This provides new functionality using anisotropic layered black phosphorus, thereby enabling novel optical and optoelectronic device applications.Comment: 18 pages, 5 figures in Nature Nanotechnology 201

Thermally drawn multifunctional fibers: toward the next generation of information technology

As the fundamental building block of optical fiber communication technology, thermally drawn optical fibers have fueled the development and prosperity of modern information society. However, the conventional step-index configured silica optical fibers have scarcely altered since their invention. In recent years, thermally drawn multifunctional fibers have emerged as a new yet promising route to enable unprecedented development in information technology. By adopting the well-developed preform-to-fiber manufacturing technique, a broad range of functional materials can be seamlessly integrated into a single fiber on a kilometer length scale to deliver sophisticated functions. Functions such as photodetection, imaging, acoustoelectric detection, chemical sensing, tactile sensing, biological probing, energy harvesting and storage, data storage, program operation, and information processing on fiber devices. In addition to the original light-guiding function, these flexible fibers can be woven into fabrics to achieve large-scale personal health monitoring and interpersonal communication. Thermally drawn multifunctional fibers have opened up a new stage for the next generation of information technology. This review article summarizes an overview of the basic concepts, fabrication processes, and developments of multifunctional fibers. It also highlights the significant progress and future development in information applications. (Figure presented.).Agency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)Nanyang Technological UniversityNational Research Foundation (NRF)Published versionThis work was supported by the National Natural Science Foundation of China (52172249, 62005101, and 51976215), the Scientific Instrument Developing Project of the Chinese Academy of Sciences (YJKYYQ20200017), and the Funding of Innovation Academy for Light-duty Gas Turbine, Chinese Academy of Sciences (CXYJJ21-ZD-02). This work was supported by the Singapore Ministry of Education Academic Research Fund Tier 2 (MOE2019-T2-2-127 and MOE-T2EP50120-0002), A*STAR under AME IRG (A2083c0062), the Singapore Ministry of Education Academic Research Fund Tier 1 (MOE2019-T1-001-103 (RG 73/19) and MOE2019-T1-001-111 (RG90/19)), and the Singapore National Research Foundation Competitive Research Program (NRF-CRP18-2017-02). This work was partly supported by the Schaeffler Hub for Advanced Research at NTU, under the ASTAR IAF-ICP Programme ICP1900093. This work was also supported by Nanyang Technological University

Comparison of Neoatherosclerosis and Neovascularization of Restenosis after Drug-Eluting Stent Implantation: An Optical Coherence Tomography Study

Background: Neoatherosclerosis (NA) is associated with stent failure. However, systematic studies on the manifestations of NA and neovascularization (NV) at different stages after drug-eluting stent (DES) implantation are lacking. Moreover, the relationship between NA and NV in in-stent restenosis (ISR) has not been reported. This study aimed to characterize NA and NV in patients with ISR at different post-DES stages and compare the association between NA and NV in ISR lesions. Methods: A total of 227 patients with 227 lesions who underwent follow-up optical coherence tomography before percutaneous coronary intervention for DES ISR were enrolled and divided into early (E-ISR: 5 years) ISR groups. Furthermore, ISR lesions were divided into NV and non-NV groups according to the presence of NV. Results: The prevalence of NA and NV was 52.9% and 41.0%, respectively. The prevalence of lipidic NA (E-ISR, 32.7%; L-ISR, 50.0%; VL-ISR, 58.5%) and intimal NV (E-ISR, 14.5%; L-ISR, 30.8%; VL-ISR, 38.3%) increased with time after stenting. NA was higher in ISR patients with NV lesions than in those without (p < 0.001). Patients with both ISR and NV had a higher incidence of macrophage infiltration, thin-cap fibroatheroma, intimal rupture, and thrombosis (p < 0.01). Conclusions: Progression of lipidic NA was associated with L-ISR and VL-ISR but may not be related to calcified NA. NA was more common in ISR lesions with NV; its formation may substantially promote NA progression and plaque instability

Controlled fragmentation of single-atom-thick polycrystalline graphene

Controlling the fragmentation of atomically thin and brittle materials is of critical importance for both fundamental interest and technical purposes in fracture mechanics. However, the fragmentation of graphene is often random and uncontrollable because of the presence of grain boundaries and numerous defects. Here, by harnessing the strong localized strain during the necking process of thermoplastic polymers, we introduce a simple yet controllable method to tear apart a monolayer polycrystalline graphene (MPG) sheet into ordered graphene ribbons. More importantly, we show that the presence of active edges helps the graphene ribbons in exhibiting a field-effect characteristic pH response and improves the introduction of dopants. Furthermore, we demonstrate an optically transparent (∼98%), ultrathin (∼70 ± 15 nm), and skin-conformal pressure sensor for real-time tactile sensing. We believe that our results lead to further understanding of the fracture mechanics of graphene and offer unique advantages for practical applications, such as flexible electronics, chemical sensing, and biosensing.Ministry of Education (MOE)National Research Foundation (NRF)This work was supported in part by the Singapore Ministry of Education Academic Research Fund Tier 2 (MOE2015-T2-2-010) and the Singapore Ministry of Education Academic Research Fund Tier 1 (MOE 2019-T1-001-103 and MOE2019-T1-001- 111). This work was supported in part by the EEE Ignition Research Grant. This work was supported in part by the National Nature Science Foundation of China: 11804354. M.T. and K.F. acknowledge the Air Force Office of Scientific Research (AFOSR) grant 17RT0244. T.Z. acknowledges the Bureau of International Cooperation of Chinese Academy of Sciences, International Partnership Program grant 182211KYSB20170029. This work was supported in part by the Singapore National Research Foundation under NRF award numbers NRF-NRFF2013-08 and NRFCRP13-2014-05

Evolution of the Valley Position in Bulk Transition-Metal Chalcogenides and Their Monolayer Limit.

Layered transition metal chalcogenides with large spin orbit coupling have recently sparked much interest due to their potential applications for electronic, optoelectronic, spintronics, and valleytronics. However, most current understanding of the electronic structure near band valleys in momentum space is based on either theoretical investigations or optical measurements, leaving the detailed band structure elusive. For example, the exact position of the conduction band valley of bulk MoS2 remains controversial. Here, using angle-resolved photoemission spectroscopy with submicron spatial resolution (micro-ARPES), we systematically imaged the conduction/valence band structure evolution across representative chalcogenides MoS2, WS2, and WSe2, as well as the thickness dependent electronic structure from bulk to the monolayer limit. These results establish a solid basis to understand the underlying valley physics of these materials, and also provide a link between chalcogenide electronic band structure and their physical properties for potential valleytronics applications