7 research outputs found
Instantaneous band gap collapse in photoexcited monoclinic VO due to photocarrier doping
Using femtosecond time-resolved photoelectron spectroscopy we demonstrate
that photoexcitation transforms monoclinic VO quasi-instantaneously into a
metal. Thereby, we exclude an 80 femtosecond structural bottleneck for the
photoinduced electronic phase transition of VO. First-principles many-body
perturbation theory calculations reveal a high sensitivity of the VO
bandgap to variations of the dynamically screened Coulomb interaction,
supporting a fully electronically driven isostructral insulator-to-metal
transition. We thus conclude that the ultrafast band structure renormalization
is caused by photoexcitation of carriers from localized V 3d valence states,
strongly changing the screening \emph{before} significant hot-carrier
relaxation or ionic motion has occurred
Graphene/-RuCl: An Emergent 2D Plasmonic Interface
Work function-mediated charge transfer in graphene/-RuCl
heterostructures has been proposed as a strategy for generating highly-doped 2D
interfaces. In this geometry, graphene should become sufficiently doped to host
surface and edge plasmon-polaritons (SPPs and EPPs, respectively).
Characterization of the SPP and EPP behavior as a function of frequency and
temperature can be used to simultaneously probe the magnitude of interlayer
charge transfer while extracting the optical response of the interfacial doped
-RuCl. We accomplish this using scanning near-field optical
microscopy (SNOM) in conjunction with first-principles DFT calculations. This
reveals massive interlayer charge transfer (2.7 10 cm)
and enhanced optical conductivity in -RuCl as a result of
significant electron doping. Our results provide a general strategy for
generating highly-doped plasmonic interfaces in the 2D limit in a scanning
probe-accessible geometry without need of an electrostatic gate.Comment: 22 pages, 5 figure
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Charge-Transfer Plasmon Polaritons at Graphene/alpha-RuCl3 Interfaces
Work function-mediated charge transfer in graphene/-RuCl
heterostructures has been proposed as a strategy for generating highly-doped 2D
interfaces. In this geometry, graphene should become sufficiently doped to host
surface and edge plasmon-polaritons (SPPs and EPPs, respectively).
Characterization of the SPP and EPP behavior as a function of frequency and
temperature can be used to simultaneously probe the magnitude of interlayer
charge transfer while extracting the optical response of the interfacial doped
-RuCl. We accomplish this using scanning near-field optical
microscopy (SNOM) in conjunction with first-principles DFT calculations. This
reveals massive interlayer charge transfer (2.7 10 cm)
and enhanced optical conductivity in -RuCl as a result of
significant electron doping. Our results provide a general strategy for
generating highly-doped plasmonic interfaces in the 2D limit in a scanning
probe-accessible geometry without need of an electrostatic gate
Ultrasensitive HâS gas sensors based on p-type WSâ hybrid materials
Abstract
Owing to their higher intrinsic electrical conductivity and chemical stability with respect to their oxide counterparts, nanostructured metal sulfides are expected to revive materials for resistive chemical sensor applications. Herein, we explore the gas sensing behavior of WSâ nanowire-nanoflake hybrid materials and demonstrate their excellent sensitivity (0.043 ppmâ»Âč) as well as high selectivity towards HâS relative to CO, NHâ, Hâ, and NO (with corresponding sensitivities of 0.002, 0.0074, 0.0002, and 0.0046 ppmâ»Âč, respectively). Gas response measurements, complemented with the results of X-ray photoelectron spectroscopy analysis and first-principles calculations based on density functional theory, suggest that the intrinsic electronic properties of pristine WSâ alone are not sufficient to explain the observed high sensitivity towards HâS. A major role in this behavior is also played by O doping in the S sites of the WSâ lattice. The results of the present study open up new avenues for the use of transition metal disulfide nanomaterials as effective alternatives to metal oxides in future applications for industrial process control, security, and health and environmental safety