A MoSe2 p-n diode with a van der Waals homojunction is demonstrated by stacking undoped (n-type) and Nb-doped (p-type) semiconducting MoSe2 synthesized by chemical vapor transport for Nb substitutional doping. The p-n diode reveals an ideality factor of ≈1.0 and a high external quantum efficiency (≈52%), which increases in response to light intensity due to the negligible recombination rate at the clean homojunction interface.

Single-crystalline monolayer hexagonal WS is segmented into alternating triangular domains: sulfur-vacancy (SV)-rich and tungsten-vacancy (WV)-rich domains. The WV-rich domain with deep-trap states reveals an electron-dedoping effect, and the electron mobility and photoluminescence are lower than those of the SV-rich domain with shallow-donor states by one order of magnitude. The vacancy-induced strain and doping effects are investigated via Raman and scanning photoelectron microscopy.

In this paper, the feasibility of utilization of a single element double split-ring resonator as a biosensing device has been demonstrated. The compact resonator has been excited by time-varying magnetic fields generated from the 50 Ω microstrip transmission line. In this work, DNA hybridization is recognized with shift in S21 resonant frequency. When thiol-linked single stranded-DNA is immobilized onto a gold (Au) surface and is then coupled with complementary-DNA, the frequency changes by Δfss-DNA=20 MHz and Δfhybridization=60 MHz, respectively. Thus, it is clear that the resonator can be utilized as a DNA sensing element in the microwave regime.

Among two dimensional (2D) van der Waals (vdW) layered materials such as graphene, which is used like a metal, and transition metal chalcogenides (TMdCs), which are used as semiconductors and metals, hexagonal boron nitride (hBN), which is used as an insulator, is ubiquitous as a building block to construct 2D vdW electronics for versatile tunneling devices. Monolayer and few-layer hBN films have been prepared with flake sizes of a few hundred micrometer via mechanical exfoliation and transfer methods. Another approach used to synthesize hBN films on a large scale is chemical vapor deposition (CVD). Although the single-crystal film growth of hBN on the wafer scale is the key to realizing realistic electronic applications, the various functionalities of hBN for 2D electronics are mostly limited to the microscale. Here, we review the recent progress for the large-area synthesis of hBN and other related vdW heterostructures via CVD, and the artificial construction of vdW heterostructures and 2D vdW electronics based on hBN, in terms of charge fluctuations, passivation, gate dielectrics, tunneling, Coulombic interactions, and contact resistances. The challenges and future perspectives for practical applications are also addressed.

However, their inherent drawback is weak light absorption by their atomically thin layer [6].The use of the local-field enhancement effect of localized surface plasmons via hybridization with metal nanostructures is a promising way to enhance the optoelectronic performance of TMDs [1,[6][7][8]. However, this approach is challenging because coherent tuning between the plasmon resonance and the optical wavelength must be precisely engineered [7][8][9][10], and the mechanism of the interaction between surface plasmon polaritons (SPPs) and the intricate excitons of TMDs must be understood [11][12][13][14][15][16][17].Here, we propose a cavity-free method to enhance the exciton emission performance of TMD semiconductors under varying excitation laser power (Pex) without sacrificing peak quality and shape. We used nanowire (NW)-TMD emitter hybrids in this study (Methods [18]). The Ag-NW partly overlapping on the monolayer MoS2 from which it was separated by a SiO2 (10 nm) spacer to prevent band-pinning, doping, and photoluminescence (PL) quenching from direct metal-semiconductor contact [19,20]. Figure 1 [20][21][22]. The PL signals were collected at the same LIP indicated by a white arrow. Figure 1(c) shows the normalized PL spectra that were deconvoluted using a Lorentzian function.The unknown X peak for Off-NW is presumably a localized state due to defects or impurities [23]. At all five Pex levels (5-500 μW), only the A 0 observation for On-NW is markedly different from the PL spectra for Off-NW which have three exciton modes. ForOn-NW, the A-peak position of ~1.88 eV and full-width at half-maximum (FWHM) of ~50 meV remain unchanged and independent of Pex. However, for Off-NW, as Pex increases, the A-peak center position redshifts considerably because the A' dominates the A-peak, and the intensities of A' and B increase. 3(c)] during laser illumination at the NMOR. In Fig 3(a), the left image indicates the LIP (green arrow) and the right image indicates the PL collecting positions for the LIP and the NWEP (white arrows). At the LIP, ε-factor reaches ~7 selectively for the A 0 [ Fig. 3(b)]. The A 0 selectivity is confirmed by subtracting the PL spectrum for Off-NW from that of On-NW (which yields ΔPL) and the A 0 is identified exclusively via a SLF. [ Fig. 3(b), inset].In linear-scale PL spectra collected at the NWEP [ Fig. 3(c), inset], the A 0 also dominates A-peak for all Pex. Interestingly, the log-scale plot of the spectra [ Fig

SUMMARY BackgroundWhether the incidence of metachronous gastric dysplasia and cancer could be decreased by eradication of Helicobacter pylori after endoscopic submucosal dissection (ESD) for early gastric cancer (EGC).

The extreme elastic strain of monolayer transition metal dichalcogenides provides an ideal platform to achieve efficient exciton funneling via local strain modulation; however, studies conducted thus far have focused on the use of substrates with fixed strain profiles. We prepared 1L-WS 2 on a flexible substrate such that the formation of topographic wrinkles could be switched on or off, and the depth or the direction of the wrinkle could be modified by external strain, thereby providing full control of the periodic undulation of the band gap profile of 1L-WS 2 in the range 0−57 meV. Nanoscale photoluminescence (PL) imaging unambiguously evinced that the photoexcited excitons of 1L-WS 2 were accumulated at the top regions of the wrinkles with less band gap than the valley region. Our results of broad tunability of the two-dimensional (2D) exciton funneling suggest a promising route to control exciton drift for enhanced optoelectronic performances and future 2D exciton devices.

Vertically stacked van der Waals (vdW) heterostructures have been suggested as a robust platform for studying interfacial phenomena and related electric/optoelectronic devices. While the interlayer Coulomb interaction mediated by the vdW coupling has been extensively studied for carrier recombination processes in a diode transport, its correlation with the interlayer tunneling transport has not been elucidated. Here, a contrast is reported between tunneling and drift photocurrents tailored by the interlayer coupling strength in MoSe /MoS hetero-bilayers (HBs). The interfacial coupling modulated by thermal annealing is identified by the interlayer phonon coupling in Raman spectra and the emerging interlayer exciton peak in photoluminescence spectra. In strongly coupled HBs, positive photocurrents are observed owing to the inelastic band-to-band tunneling assisted by interlayer excitons that prevail over exciton recombinations. By contrast, weakly coupled HBs exhibit a negative photovoltaic diode behavior, manifested as a drift current without interlayer excitonic emissions. This study sheds light on tailoring the tunneling transport for numerous optoelectronic HB devices.