Graphene films grown on Cu foils have been fluorinated with xenon difluoride (XeF(2)) gas one or both sides. When exposed side the F coverage saturates at 25% (C(4)F), which is optically transparent, over 6 orders of magnitude more resistive than graphene, and readily patterned. Density functional calculations for varying coverages indicate that a C(4)F configuration lowest in energy calculated band gap increases increasing coverage, becoming 2.93 eV configuration. During defluorination, we...

We report the first observation of linear magnetoresistance (LMR) in multilayer epitaxial graphene grown on SiC. show that exhibits large LMR from 2.2 K up to room temperature and it can be best explained by a purely quantum mechanical model. attribute inhomogeneities epitaxially film. The magnitude suggests potential for novel applications areas such as high-density data storage magnetic sensors actuators.

Epitaxial graphene (EG) films were grown in vacuo by silicon sublimation from the (0001) and (0001¯) faces of 4H-SiC 6H-SiC. Hall effect mobilities sheet carrier densities measured at 300 77 K data depended on growth face. About 40% samples exhibited holes as dominant carrier, independent Generally, increased with decreasing density, type substrate polytype. The contributions scattering mechanisms to conductivities are discussed. results suggest that for near-intrinsic epitaxial will be ∼150...

To make graphene technologically viable, the transfer of films to substrates appropriate for specific applications is required. We demonstrate dry epitaxial (EG) from C-face 4H-SiC onto SiO2, GaN and Al2O3 using a thermal release tape. Subsequent Hall effect measurements illustrated that minimal degradation in carrier mobility was induced following process lithographically patterned devices. Correspondingly, large drop concentration observed process, supporting notion gradient density...

Heterostructures composed of multiple layers different atomically thin materials are interest due to their unique properties and potential for new device functionality. MoS 2 ‐graphene heterostructures have shown promise as photodetectors vertical tunnel transistors. However, progress is limited by the typically micrometer‐scale devices alignments required fabrication when utilizing mechanically exfoliated material. Here, synthesis large‐area, continuous, uniform monolayers directly on...

Monolayer WS2 offers great promise for use in optical devices due to its direct bandgap and high photoluminescence intensity. While fundamental investigations can be performed on exfoliated material, large-area quality materials are essential implementation of technological applications. In this work, we synthesize monolayer under various controlled conditions characterize the films using photoluminescence, Raman x-ray photoelectron spectroscopies. We demonstrate that introduction hydrogen...

Direct, tunable coupling between individually assembled graphene layers is a next step towards designer two-dimensional (2D) crystal systems, with relevance for fundamental studies and technological applications. Here we describe the fabrication characterization of large-area (> cm^2), coupled bilayer on SiO2/Si substrates. Stacking two films leads to direct electronic interactions layers, where resulting film properties are determined by local twist angle. Polycrystalline have...

Epitaxial graphene layers were grown on the C-face of 4H- and 6H-SiC using an argon-mediated growth process. Variations in temperature pressure found to dramatically affect morphological properties layers. The presence argon during slowed rate formation led observation islanding. similarity morphology islands continuous films indicated that island nucleation coalescence is mechanism for graphene.

Abstract Near‐field plasmonic coupling and local field enhancement in metal nanoarchitectures, such as arrangements of nanoparticle clusters, have application many technologies from medical diagnostics, solar cells, to sensors. Although nanoparticle‐based cluster assemblies exhibited signal enhancements surface‐enhanced Raman scattering (SERS) sensors, it is challenging achieve high reproducibility SERS response using low‐cost fabrication methods. Here an innovative method developed for...

We investigate hyperthermal ion implantation (HyTII) as a means for substitutionally doping layered materials such graphene. In particular, this systematic study characterizes the efficacy of substitutional N-doping graphene using HyTII over an N+ energy range 25–100 eV. Scanning tunneling microscopy results establish incorporation N substituents into lattice during processing. illustrate differences in evolution characteristic Raman peaks following incremental doses N+. use ratios...

Abstract Two-dimensional (2D) materials offer unique opportunities in engineering the ultrafast spatiotemporal response of composite nanomechanical structures. In this work, we report on high frequency, quality factor ( Q ) 2D acoustic cavities operating 50–600 GHz frequency f range with × up to 1 10 14 . Monolayer steps and material interfaces expand cavity functionality, as demonstrated by building adjacent that are isolated or strongly-coupled, well a comb generator MoS 2 /h-BN systems....

We report a method to introduce direct bonding between graphene platelets that enables the transformation of multilayer chemically modified (CMG) film from "paper mache-like" structure into stiff, high strength material. On basis chemical/defect manipulation and recrystallization, this technique allows wide-range engineering mechanical properties (stiffness, strength, density, built-in stress) in ultrathin CMG films. A dramatic increase Young's modulus (up 800 GPa) enhanced (sustainable...

Abstract Electron-donors can impart charge to the surface of transition metal dichalcogenide (TMD) films while interacting with film via a weak physisorption bond, making them ideal for vapor and gas sensors. We expose monolayer MoS 2 MoSe strong electron-donor chemical analytes. After analyzing resultant behavior taking into consideration doping effects, we conclude that exposure electron-donors could be method inducing semiconductor-metal 2H-1T TMD phase transition. find conductance...

To suppress severe self-heating under high power density, we herein demonstrate top-gate nano-membrane <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\beta }$ </tex-math></inline-formula> -gallium oxide ( -Ga <sub xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) field effect transistors on a thermal conductivity diamond substrate. The devices...

We report room-temperature negative magnetoresistance in ferromagnet–graphene–ferromagnet (FM|Gr|FM) junctions with minority spin polarization exceeding 80%, consistent predictions of strong filtering. fabricated arrays such via chemical vapor deposition multilayer graphene on lattice-matched single-crystal NiFe(111) films and standard photolithographic patterning etching techniques. The exhibit metallic transport behavior, low resistance, the characteristic a filter interface throughout...

A thin cubic-GaN epitaxial layer was grown by plasma-assisted molecular-beam epitaxy directly on a (100) cubic-boron-nitride nucleation that previously deposited (100)-oriented, type IIA, single-crystal chemical-vapor deposition diamond substrate. X-ray diffraction measurements verified (100)-plane zincblende is the dominant crystal structure of GaN layer, with small contribution from wurtzite phase in some sample regions. Detailed atomic force microscopy and Raman scattering confirmed XRD...

The increasing complexity of semiconductor devices fabricated from wide-bandgap and ultra-wide-bandgap materials demand advanced thermal management solutions to mitigate heat buildup, a major cause device failure. High conductivity are thus becoming crucial for management. Cubic boron arsenide (c-BAs) has emerged as promising candidate. However, challenges remain in synthesizing high-quality crystals with low defect concentrations, high homogeneous conductivity, yields using the conventional...

While coupling between optical, electronic, and mechanical domains is paramount for high-frequency acoustic devices, materials that offer tunability in the degree of such can be crucially enabling expanding device functionality. Here, we show interaction photons with coherent phonons confined 2D layered semiconducting cavities controlled through either modifying material state via a thermally induced electronic bandgap shift (EBS) or altering polarization incoming when optical birefringence...

We demonstrate the first successful growth of large-area (200 × 200 μm(2)) bilayer, Bernal stacked, epitaxial graphene (EG) on atomically flat, 4H-SiC (0001) step-free mesas (SFMs) . The use SFMs for resulted in complete elimination surface step-bunching typically found after EG conventional nominally on-axis SiC substrates. As a result heights features are reduced by at least factor 50 from Evaluation across SFM using Raman 2D mode indicates stacking with low and uniform compressive lattice...

Cubic boron arsenide (c-BAs) exhibits an ultrahigh thermal conductivity (κ) approaching 1300 Wm−1 K−1 at room temperature. However, c-BAs is believed to incorporate high concentrations of crystal imperfections that can both quench κ and act as sources unintentional p-type conductivity. Although this behavior has been attributed native defects, we show here, using optical magnetic resonance spectroscopies together with first-principles calculations, acceptor impurities such silicon and/or...

GaN decomposition is studied at metallorganic vapor phase epitaxy pressures (i.e., 10–700 Torr) in flowing H2. For temperatures ranging from 850 to 1050 °C, the rate accelerated when H2 pressure increased above 100 Torr. The Ga desorption found be independent of pressure, and therefore, does not account for enhanced rate. Instead, excess decomposed forms droplets on surface which, identical annealing conditions, increase size as increased. Possible connections between rate, coarsening...

Ultra-thin transition metal dichalcogenides (TMDs) films show remarkable potential for use in chemical vapor sensing devices. Electronic devices fabricated from TMD are inexpensive, inherently flexible, low-power, amenable to industrial-scale processing because of emergent growth techniques, and have shown high sensitivity selectivity electron donor analyte molecules important explosives nerve gas detection. However, reported date, the conductance response vapors is dominated by Schottky...

The interaction between two-dimensional crystals (2DCs) and metals is ubiquitous in 2D material research. Here we report how 2DC overlayers influence the recrystallization of relatively thick metal films subsequent synergetic benefits this provides for coupling surface plasmon-polaritons (SPPs) to photon emission semiconductors. We show that annealing 2DC/Au on SiO2 results a 'reverse epitaxial' process where initially nanocrystalline Au become highly textured close crystallographic registry...