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Pristine topological insulators (TIs) with no carrier doping principally suffer from a lack of magnetic ordering. We create a nanomesh structure, a honeycomblike array of hexagonal nanopores with extremely high density, on a nondoped two-dimensional (2D) thin TI (Bi2Te3). We observe antiferromagnetism (AFM) in completely hydrogen-terminated nanomeshes, while it is eliminated by ferromagnetism (FM) in completely O-terminated nanomeshes. Interplay between the AFM and FM is observed in partially O-terminated nanomeshes. As a possible origin for the observed magnetisms, Kramers doublets, which may exist around nanopore edges, for AFM and those eliminated by FM spin alignment due to O-Te coupling along pore edges are discussed based on the structure and annealing dependence of the magnetisms. The nondoped 2D nanomesh formed on a TI will lead to new avenues of research on topological magnetisms and spintronics.

Plasmonic absorbers with optical cavity are fabricated using deposition of thin gold films on both sides of nanoporous anodic aluminum oxide (AAO) microcantilevers. Photothermal/opto-calorimetric responses of the microcantilevers are investigated with respect to various pore sizes and gold coating thicknesses. Photothermal/opto-calorimetric response of the AAO cantilever is significantly amplified when the thickness of the gold layer is at 40 nm due to scattering and trapping of infrared (IR) radiation in the gold nanomesh/AAO nanochannels/gold layer structure. Unlike previous photothermal IR spectroscopy of adsorbed molecules with a bimetallic AAO cantilever, the reversed IR spectra are obtained due to significantly amplified baseline photothermal signal and IR absorption of free molecules. Molecular detection sensitivity is enhanced by an order of magnitude compared with the previous photothermal IR spectroscopy of adsorbed molecules on a bimetallic AAO cantilever. The acetone vapor molecules are select...

The formation of magnetic and spintronic devices using two-dimensional (2D) atom-thin layers has attracted attention. Ferromagnetisms (FMs) arising from zigzag-type atomic structure of edges of 2D atom-thin materials have been experimentally observed in graphene nanoribbons, hydrogen (H)-terminated graphene nanomeshes (NMs), and few-layer oxygen (O)-terminated black phosphorus NMs. Herein, we report room-temperature edge FM in few-layer hexagonal boron-nitride (hBN) NMs. O-terminated hBNNMs annealed at 500 °C show the largest FM, while it completely disappears in H-terminated hBNNMs. When hBNNMs are annealed at other temperatures, amplitude of the FM significantly decreases. These are highly in contrast to the case of graphene NMs but similar to the cases of black phosphorus NM and suggest that the hybridization of the O atoms with B(N) dangling bonds of zigzag pore edges, formed at the 500 °C annealing, strongly contribute to this edge FM. Room-temperature FM realizable only by exposing hBNNMs into air opens the way for high-efficiency 2D flexible magnetic and spintronic devices without the use of rare magnetic elements.

A hybrid structure of a graphene nanomesh with the gold nanodisks is studied to enhance the light absorption by the localized surface plasmon resonance. From the reflection spectra of the visible range for graphene nanomesh samples without and with nanodisks, it is found that the absorption of graphene nanomesh structures is greatly enhanced in the presence of gold nanodisks around the resonance wavelength. Simulation results based on the finite-difference time-domain method support the experimental observations. This study demonstrates the potential of constructing graphene based photodetectors with a high light absorption efficiency and wavelength selectivity.

X-ray photoelectron spectroscopic and scanning tunneling microscopic results demonstrate that annealing of Fe/carbon-rich 6H-SiC(0001) surface between 650 and 750 °C leads to Fe intercalation under the surface carbon layer. Accompanied with the metal intercalation, the carbon nanomesh surface was transformed into a graphene surface. Moreover, the formed graphene layers always float out to the topmost surface even after deposition of more than 10 monolayer Fe, acting as a surfactant. Using graphene as the surfactant may not only promote the 2D growth but also can improve the film performance considering that graphene is stable and robust.

Graphene is intrinsically ultra-stiff in its plane. Its huge mechanical mismatch when interfacing with ultra-compliant biological tissues and elastomers (7–9 orders of magnitude difference in stiffness) poses significant challenge in its application to functional devices such as epidermal electronics and sensing prosthesis. We offer a feasible and promising solution to this significant challenge by suitably patterning graphene into a nanomesh. Through systematic coarse-grained simulations, we show that graphene nanomesh can be made extremely compliant with nearly zero stiffness up to about 20% elongation and then remain highly compliant up to about 50% elongation.

We study the elastic response of graphene nanomeshes based on molecular-statics and molecular-dynamics simulations of uniaxial tensile deformation tests. Elastic properties are determined as a function of the nanomesh architecture, namely, the lattice arrangement of the pores, pore morphology, material density (ρ), and pore edge passivation, and scaling laws for the density dependence of the elastic modulus M, M(ρ), are established. We find that, for circular unpassivated pores, M scales with the square of ρ. Deviations from quadratic scaling are most strongly influenced by pore morphology and, to a lesser extent, by pore edge passivation and temperature.

N-type doping of graphene with long-term chemical stability in air represents a significant challenge for practical application of graphene electronics. This paper reports a reversible doping method to achieve highly stable n-type graphene nanomeshes, in which the SU-8 photoresist simultaneously serves as an effective electron dopant and an excellent encapsulating layer. The chemically stable n-type characteristics of the SU-8 doped graphene were evaluated in air using their Raman spectra, electrical transport properties, and electronic band structures. The SU-8 doping does minimum damage to the hexagonal carbon lattice of graphene and is completely reversible by removing the uncrosslinked SU-8 resist.

The promise of graphene for use as a vapor sensor motivated exploration of the vapor responses of graphene nanomesh (GNM) functionalized with single stranded DNA. Devices detected different vapor types, including carboxylic acids, aldehydes, organophosphates, and explosives. As-fabricated GNM field effect transistors (FETs) had larger vapor responses than standard graphene FETs due to the effect of oxidized edges and lattice defects. DNA-GNM devices discriminated between homologous species with detection limits of a few parts per million, with fast response and recovery. Responses varied significantly when the base sequence of the DNA was changed, making the sensor class an intriguing candidate for use in an electronic nose system.

Herein, we report a simple and facile method on the direct formation of graphene nanomesh (GNM) on insulating substrates by chemical vapor deposition using the Au metal nano-network as a metal catalyst. Well-ordered hexagonal honeycomb shapes of Au nano-network films synthesized using an anodized aluminum oxide template, served as catalysts for the growth of GNM. As-prepared GNM was characterized by various techniques and fabricated as a conducting channel in field effect transistors. Enhanced mobility and a relatively high ON/OFF ratio confirmed our synthetic strategy of the fabrication of GNM as an alternative to a conventional top-down lithographic approach.

We have fabricated a metallic nanomesh using nanosphere lithography and metal evaporation. The metallic nanomesh has a precisely controlled nanostructure showing excellent uniformity with hexagonally arrayed periodic circular holes. A P3HT:PCBM organic solar cell, with the gold nanomesh electrode, demonstrates a high fill factor of 61% and a considerable power conversion efficiency of 3.12%. Electromagnetic simulation indicates that the optical properties of the metallic nanomesh can be optimized for organic photovoltaic devices by tuning the film thickness, hole diameter, and periodicity. These results show the promising potential of using a metallic nanomesh as the transparent electrode in organic solar cells.

C60 molecules adsorbed on graphene/Ru(0001) substrate were investigated by scanning tunneling microscopy (STM) at 5 K. On high quality substrates, C60 molecules adopt a commensurate growth mode, leading to formation of a supramolecular structure with perfect periodicity and few defects. On under-annealed substrates with imperfections and domains, the molecules form the same closely packed hexagonal structures in spite of underlying corrugations, disorders or steps, indicating a weak molecule-substrate interaction—a conclusion that is also supported by DFT calculations. This system may be beneficial to the fabrication of carbon based devices and of other types of organic functional overlayers.

The authors report the fabrication of heterojunction light emitting diodes (LEDs) based on two-dimensional (2D) hexagonal ordered n-type ZnO nanomesh and p-type GaN. The 2D ZnO nanomesh array was prepared by employing polystyrene spheres as a template. When a forward bias was applied to the LED, a strong ultraviolet (UV) electroluminescence peaked at 385 nm can be observed. The peak deconvolution revealed three emission peaks at 370, 388, and 420 nm. The origin of these emission peaks will be discussed. In addition, the LED was capable of exciting a red phosphor to convert UV light into red light.

A simple and inexpensive method of fabricating a nanofluidic filter was developed by using self-assembly of colloidal nanospheres and surface tension. Colloid plug formed by surface tension in the microchannel was evaporated, then the nanospheres in a colloid were orderly stacked by capillary force. The porosity and mean pore size of the nanomesh membrane were 45.4% and 158nm, respectively. In the nanoindentation test with a spherical tip of 10μm radius, the nanomesh membranes withstood the maximum mechanical loading of 26.8±2.47mN, and the heat-treated membranes withstood 66.65±4.15mN.