다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical Properties

https://cyberleninka.org/article/n/323323.pdf

Production and processing of graphene and 2d crystals

https://absimage.aps.org/image/MAR14/MWS_MAR14-2014-020819.pdf

Van der Waals heterostructures

In this paper, we present a study of tungsten disulfide (WS2) two-dimensional (2D) crystals, grown on epitaxial Graphene. In particular, we have employed scanning electron microscopy (SEM) and µRaman spectroscopy combined with multifunctional scanning probe microscopy (SPM), operating in peak force–quantitative nano mechanical (PF-QNM), ultrasonic force microscopy (UFM) and electrostatic force microscopy (EFM) modes. This comparative approach provides a wealth of useful complementary information and allows one to cross-analyze on the nanoscale the morphological, mechanical, and electrostatic properties of the 2D heterostructures analyzed. Herein, we show that PF-QNM can accurately map surface properties, such as morphology and adhesion, and that UFM is exceptionally sensitive to a broader range of elastic properties, helping to uncover subsurface features located at the buried interfaces. All these data can be correlated with the local electrostatic properties obtained via EFM mapping of the surface potential, through the cantilever response at the first harmonic, and the dielectric permittivity, through the cantilever response at the second harmonic. In conclusion, we show that combining multi-parametric SPM with SEM and µRaman spectroscopy helps to identify single features of the WS2/Graphene/SiC heterostructures analyzed, demonstrating that this is a powerful tool-set for the investigation of 2D materials stacks, a building block for new advanced nano-devices.

https://www.mdpi.com/2079-4991/10/12/2494/pdf

Scanning Probe Spectroscopy of WS2/Graphene Van Der Waals Heterostructures.

We study surface charge transfer doping of exfoliated black phosphorus (bP) flakes by copper using scanning tunneling microscopy (STM) and spectroscopy (STS) at room temperature. The tunneling spectra reveal a gap in correspondence of Cu islands, which is attributed to Coulomb blockade phenomena. Moreover, using line spectroscopic measurements across small copper islands, we exploit the potential of the local investigation, showing that the n-type doping effect of copper on bP is short-ranged. These experimental results are substantiated by first-principles simulations, which quantify the role of cluster size for an effective n-type doping of bP and explain the Coulomb blockade by an electronic decoupling of the topmost bP layer from the underlying layers driven by the copper cluster. Our results provide novel understanding –difficult to retrieve by transport measurements– of the doping of bP by copper, which appears promising for the implementation of ultra-sharp p-n junctions in bP. Introduction Black phosphorus (bP) is a semiconductor with a direct band gap that ranges from ∼ 0.3 eV (bulk) to ∼ 2.0 eV (monolayer) depending on layer thickness.1–3 Among the van der Waals elemental materials,4,5 bP in its few-layer form attracted great interest since its first exfoliation6,7 because of the modulation of the direct band gap,4,8 the in-plane anisotropy,9–11 and its high charge-carrier mobility, up to 5,200 cm/(V· s) at room temperature,12 appealing for possible device applications.13 The presence of phosphorus vacancies, as reported in a recent scanning tunneling microscopy (STM) study,14 makes bP an intrinsically p-doped material.15,16 N-type doping of bP has been investigated in the light of possible applications.17 Several strategies have been pursued, from the reversible doping by field effect in transistors, where an ambipolar behaviour was obtained,1,18,19 to exfoliation of bulk crystals obtained by substitutional doping with Se20 or Te.21 A more promising strategy for few-layer flakes could be surface

Black Phosphorus n-Type Doping by Cu: A Microscopic Surface Investigation

Stacking Relations and Substrate Interaction of Graphene on Copper Foil

The control of the local strain profile in 2D materials offers an invaluable tool for tailoring the electronic and photonic properties of solid-state devices. In this paper, we demonstrate a local engineering of the exciton photoluminescence (PL) energy of monolayer tungsten disulfide (WS2) by means of strain. We apply a local uniaxial stress to WS2 by exploiting electron-beam patterned and actuated polymeric micrometric artificial muscles (MAMs), which we implement onto monolithic synthetic WS2/graphene heterostructures. We show that MAMs are able to induce an in-plane stress to the top WS2 layer of the van der Waals heterostructure and that the latter can slide on the graphene underneath with negligible friction. As a proof of concept for the local strain-induced PL shift experiments, we exploit a two-MAM configuration in order to apply uniaxial tensile stress on well-defined micrometric regions of WS2. Remarkably, our architecture does not require the adoption of fragile suspended microstructures. We observe a spatial modulation of the excitonic PL energy of the WS2 monolayers under stress, which agrees with the expected strain profile and attains a maximum redshift of about 40 meV at the maximum strain intensity point. After the actuation, a time-dependent PL blueshift is observed in agreement with the viscoelastic properties of the polymeric MAMs. Our approach enables inducing local and arbitrary deformation profiles and circumvents some key limitations and technical challenges of alternative strain engineering methods requiring the 2D material transfer and production of suspended membranes.

/pdf/local-tuning-of-ws2-photoluminescence-using-polymeric-micro-3npqt5onzv.pdf

Local tuning of WS2 photoluminescence using polymeric micro-actuators in a monolithic van der Waals heterostructure

https://iopscience.iop.org/article/10.1088/2515-7639/abd4f2/pdf

Stiven Forti

Papers

Scanning Probe Spectroscopy of WS2/Graphene Van Der Waals Heterostructures.

Black Phosphorus n-Type Doping by Cu: A Microscopic Surface Investigation

Stacking Relations and Substrate Interaction of Graphene on Copper Foil

Local tuning of WS2 photoluminescence using polymeric micro-actuators in a monolithic van der Waals heterostructure

Thermal stability of monolayer WS2 in BEOL conditions