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Nanodevices have higher requirements for nanofabrication in tuning the size, shape and spatial arrangement of nanostructures and their assemblies in nanoscale, however, which are often beyond the reach of conventional lithography or self-assembly techniques. In view of the above, we develop atomic layer assembled nanofabrication based on soft-templates to break through the limitations of traditional rigid-templates, having very well scalability and powerful fabrication capability for multiple solid or hollow nanostructures. Versatile soft-templates can be freely patterned at the nanoscale by mature lithographic processes, along which a precisely controlled atomic layer deposition can assemble high-aspect-ratio nanostructures with a flexible tailoring of the size, shape and spatial array, and then a dry etching process removes soft scaffolds and leaves freestanding nanostructures over large-area, rigid or soft substrates. To highlight the potentials of this fabrication strategy, the high-performance optical metasurface and ultra-sensitive H2 gas sensor are demonstrated. This approach endows the conventional lithography and assembly techniques with new powerful functionalities and more scalability in nanofabrication, providing a simply promising route to generating complex multiple nanostructures, towards a broad application in modern nanodevices.

Graphene-metal hybrid systems are highly promising as a very important building block in plasmonic structure for biosensing and catalyzing applications. However, the potential and mechanism of graphene in plasmon enhancement for such hybrids are not clear enough, although the corresponding enhancement of light-matter interaction has been reported. Here, we report an ultrafast optical spectroscopy investigation of a graphene/Ag-nanoparticles (NP) hybrid structure and evidence photo-carrier transfer from graphene to the Ag-NP. More importantly, we show that the graphene layer acts as an electron reservoir, and the electrons that transfer from it to the Ag-NP greatly enhance plasmon excitations therein, thereby generating giant local electromagnetic field enhancement in its hybrid. Further, we show that this graphene-derived local electromagnetic enhancement contributes greatly to ultrasensitive (10−13 M) surface-enhanced Raman scattering (SERS) in this hybrid. Our investigation reveals graphene's electromagnetic enhancement of SERS by uncovering an ultrafast carrier transfer mechanism in the graphene-plasmonic hybrid, and these results pave the way for the development of ultrasensitive plasmonic devices.

A strategy to promote the energy density of graphene-based supercapacitors by a combination of dry etching and chemical vapor deposition (CVD) techniques is demonstrated. A three dimensional (3D) electrode is composed of vertically oriented graphene that is deposited on metalized silicon nanocones. The design of the 3D electrodes improves specific surface area, electrolyte ion migration and electrical contact, resulting in an enhancement of areal capacitance and rate capability. Furthermore, a solid-state supercapacitor was prepared based on the 3D graphene electrodes and gel polymer electrolyte. The 3D electrode with 10 min of CVD growth of graphene endows the electrical double layer capacitor with the highest areal capacitance of 667.2 μF cm −2 , which is larger than that of supercapacitors with flat electrodes.

There has been increasing interest in surface-enhanced Raman scattering (SERS) due to its ability in nondestructive and efficient detection of molecules. However, the fabrication of ideal SERS substrates with large-scale, strong and uniform ‘hot spots’ was always the challenge for the commercial use of SERS. Here, we designed an Ag-nanoparticles/Al2O3/Au-nanograting hybrid nanostructure as SERS substrate, in which the deep Au nanograting was formed by nanoimprint lithography (NIL) and metal deposition process, and the isolating layer of Al2O3 was deposited by atomic layer deposition (ALD) to form the large area precisely-controlled nanogaps between nanoparticles and nanograting. This hybrid nanostructure utilized the deep metal grating and further the strong local field from multiple coupling systems to realize large-scale and uniform “hot spots”. The optimized hybrid structure substrates showed a highly uniform field enhancement, with the enhancement factor of ~ 5.2 × 107 and the sensitivity of ~ 10− 9 M, which manifested their potential and promising application in commercial use of SERS.

A simple physical method was developed to reproducibly fabricate large-scale noble metal nanosphere arrays with controllable distribution. Different from the traditional upwards annealing process, an inverted annealing method (annealing upside down samples) is introduced to treat Ag film deposited on micro-sized Si pyramid arrays. Strikingly, high density Ag nanosphere arrays can be obtained, with the gap between the nanospheres less than 20 nm under optimized conditions, which is far superior to those made by upwards annealing. The as-formed Ag-nanospheres/Si-pyramid hybrid structure exhibited a significant high enhancement factor and highly sensitive surface enhanced Raman scattering (SERS) for Rhodamine 6G molecules. Raman mapping image of this plasmonic hybrid verified a very prominent “hot spots” effect that exists around the pyramid, which contributed mainly to an enhanced SERS signal. Our work demonstrated a feasible way to prepare high-efficiency dense plasmonic nanospheres with highly localized surface plasmon resonance response, which could be feasibly applied for other bio-sensors, and also open a potential route to fabricate a metal-coated probe for tip-enhanced Raman Spectroscopy.

Current approaches to dealing with the worldwide problem of marine biofouling are to impart chemical functionality to the surface or utilize microtopography inspired by nature. Previous reports have shown that only introducing a single method may not resist adhesion of mussels or inhibit biofouling in static forms. While it is promising to integrate two methods to develop an effective antifouling strategy, related basic research is still lacking. Here, we have fabricated engineered shark skin surfaces with different feature heights and terminated with different chemical moieties. Atomic force microscopy (AFM) with a modified colloid probe technique and quartz crystal microbalance with a dissipation n (QCM-D) monitoring method have been introduced to directly determine the interactions between adhesive proteins and functionalized surfaces. Our results indicate that the adhesion strength of probe-surface decreases with increasing feature height, and it also decreases from bare Si surface to alkyl and hydroxyl modification, which is attributed to different contact area domains and interaction mechanisms. Combining biomimetic microtopography and surface chemistry, our study provides a new perspective for designing and developing underwater anti-fouling materials.

Doping with transition metal elements is an effective method to introduce magnetism in graphene, which could enable future graphene-based spintronic devices. Motivated by the recent experimental observation of a stable single layer iron membrane embedded in graphene perforation, we investigate the electronic and magnetic properties of the Fe-nanostructure-embedded graphene system based on first principles calculations. The results demonstrate that strain could lead to dramatic changes in the magnetic configurations for both small Fe clusters bonded to the edge carbon atoms of graphene perforation and the single layer Fe membrane fully embedded in the graphene layer. For optimal doping, a delicate balance can be achieved, which leads to a half-metallic electronic structure. This work suggests an easy and effective method to introduce and tune the magnetic properties of graphene, which offers a new direction for the development of future graphene-based spintronic devices.

In this work we demonstrate a fabrication process for three-dimensional (3D) container, which is composed of inverted pyramidal pit (IPP) and a cap with nanosized opening fabricated by combining laser interference lithography and anisotropic wet etching processes. The advantages of this method lie in the tunable volume of the pyramidal pit and the diameter of the nano-opening, and its wafer-scale fabrication process. To demonstrate the optical properties of this 3D container, Au film was deposited on the structure through nanosized opening to form a 3D plasmonic nanostructure including above Au hole-arrays and under Au inverted cone. A blue-shift of the absorption dip with the increasing of Au film thickness was observed by study the reflection spectra of 3D plasmonic nanostructure. Display Omitted A fabrication process for 3D submicron container by combining laser interference lithography and wet etching was proposed.The advantages of this method lie in the tunable volume of the container and the size of the opening, and its wafer-scale fabrication process.A blue-shift of the absorption dip with increasing of Au film thickness was observed by study the reflection spectra of plasmonic structures.

Dedicated Raman investigation was performed on the graphene suspended on the round holes, compared with graphene supported on Si/SiO2 substrate, in the temperature range from 173 K to 673 K. We observed an unexpected result that the temperature-dependent Raman frequency shift of suspended graphene was similar as that of supported graphene. This evidenced that the strain caused by thermal expansion coefficient mismatch between graphene and substrate cannot be neglected from suspended graphene. We predicted that the unsupported graphene zone and its surrounding graphene that adhered to substrate should be considered as a whole while studying the thermodynamic properties of this suspended graphene, and thus a semi-quantitative factor was introduced to the estimate the contribution from substrate to the suspended graphene, explaining well this result. Our results suggest that the thermal expansion coefficient mismatch induced strain should be taken into consideration in the study of electronic and transport properties of suspended graphene devices, in which the self-heating effect cannot be eliminated during operation.

Nanogap electrodes arrays are fabricated by combining atomic layer deposition, adhesive tape, and chemical etching. A unipolar nonvolatile resistive-switching behavior is identified in the nanogap electrodes, showing stable, robust performance and the multibit storage ability, demonstrating great potential in ultrahigh-density storage. The formation and dissolution of Si conductive filaments and migration of Au atoms is the mechanism behind the resistive switching.

The CVD (Chemical Vapor Deposition) diamond nanopatterning has been a great challenge due to its superhard property and chemical stability as well as rough surface, especially for fabricating high aspect ratio nanostructures such as nanowires and nanopillars. In this work, we report an approach to fabricate directly periodic high-aspect-ratio nanopillar arrays on the rough CVD-diamond film by e-beam lithography (EBL) and inductively coupled plasma (ICP) etching method. The as-fabricated diamond nanopillar arrays have a controllable aspect ratio and tunable period with good repeatability and uniformity, and the highest aspect ratio of above 10 with 200nm in diameter can be obtained. This result relies on reduced grain size of CVD-diamond and a special treatment process of the mask-patterning and then effective etching control. The fabrication process does not rely on a thick hard mask layer, but uses a just few nanometers of metal to improve mask adhesion. Masking is also improved by adjusting the growth process of diamond film to make its surface as smooth as possible. Such development of CVD-diamond nanopillar fabrication process, especially having ultrahigh aspect ratio, will likely impact the application of CVD-diamond nanostructure based nanoscale sensors, nanoelectronic devices, and NEMS/MEMS manufacturing. Display Omitted We provide a simple and effective approach to fabricate controllably CVD-diamond nanopillars.The HSQ photoresist process is used to displace traditionally complicated metallic mask process.Reduced grain size and pre/after-treatment process contributes to the whole nanofabrication.The highest aspect ratio of the nanopillar is more than 10 with 200nm in diameter and 500nm in period.As-proposed fabrication process will promisingly extend the applied range of CVD-diamond.

Compared to their 2D counterparts, 3D micro/nanostructures show larger degrees of freedom and richer functionalities; thus, they have attracted increasing attention in the past decades. Moreover, extensive applications of 3D micro/nanostructures are demonstrated in the fields of mechanics, biomedicine, optics, etc., with great advantages. However, the mainstream micro/nanofabrication technologies are planar ones; therefore, they cannot be used directly for the construction of 3D micro/nanostructures, making 3D fabrication at the micro/nanoscale a great challenge. A promising strategy to overcome this is to combine the state-of-the-art planar fabrication techniques with the folding method to produce 3D structures. In this strategy, 2D components can be easily produced by traditional planar techniques, and then, 3D structures are constructed by folding each 2D component to specific orientations. In this way, not only will the advantages of existing planar techniques, such as high precision, programmable patterning, and mass production, be preserved, but the fabrication capability will also be greatly expanded without complex and expensive equipment modification/development. The goal here is to highlight the recent progress of the folding method from the perspective of principles, techniques, and applications, as well as to discuss the existing challenges and future prospectives.

Construction of molecular devices is one of the most promising approaches for the ultimate miniaturization of electronic devices, the groundwork of which is the fabrication of nanogap electrodes. Here we report a method to fabricate nanogap electrodes through thermal annealing based on single grain boundary junction. By performing low temperature thermal process, single grain boundary junction can be broken and change into a suspended gap with gap width down to sub-5 nanometers, which is beyond the fabrication precision of traditional lithography technologies. With the advantage of shape stability, no debris and high time efficiency, such nanogap electrodes is promising in constructing molecular devices with two or three-terminals.

The charge-trapping process, with HfO2 film as the charge-capturing layer, has been investigated by using in situ electron energy-loss spectroscopy and in situ energy-filter image under positive external bias. The results show that oxygen vacancies are non-uniformly distributed throughout the HfO2 trapping layer during the programming process. The distribution of the oxygen vacancies is not the same as that of the reported locations of the trapped electrons, implying that the trapping process is more complex. These bias-induced oxygen defects may affect the device performance characteristics such as the device lifetime. This phenomenon should be considered in the models of trapping processes.

Free-standing metallic nanostructures are considered to be highly relevant to many branches of science and technology with applications of three dimensional metallic nanostructures ranging from optical reflectors, actuators, and antenna, to free-standing electrodes, mechanical, optical, and electrical resonators and sensors. Strain-induced out-of-plane fabrication has emerged as an effective method which uses relaxation of strain-mismatched materials. In this work, we report a study of the thermal annealing-induced shape modification of free-standing nanostructures, which was achieved by introducing compositional or microstructural nonuniformity to the nanowires. In particular gradient, segmented and striped hetero-nanowires were grown by focused-ion-beam-induced chemical vapor deposition, followed by rapid thermal annealing in a N2 atmosphere. Various free-standing nanostructures were produced as a result of the crystalline/grain growth and stress relief.

Display Omitted The trends of 3D surfaces metallization were studied systematically in details.New growth mechanisms has been developed.Various 3D surface structures have been constructed. Nanostructured metal surfaces, in contrast to their corresponding bulk counterparts, have increased area, redistributed surface potential energy and novel physicochemical properties, thus have great potentials to be applied in a wide range of fields. In the work, different fabrication methods were employed to produce semiconducting and polymer conic structures, to provide three-dimensional frameworks with different surface properties, e.g. morphology, microstructure and chemical composition. Followed by metal deposition, 3D metalized conic structures, e.g. Ag-Si, Au/Ni-Si, Au/Ti-Si and Au/Cr-Si pinecones, were formed. The influence of factors, including the thickness and material type of the deposited metals, the metal deposition method, and the geometry, size and material type of the conic frameworks, on the 3D surface metallization process, were investigated and the related mechanisms were discussed.

We report that vertical graphene coating can greatly improve the electrochemical performance and the interfacial stability of silicon nanocone (SNC) anodes for lithium-ion batteries. The coating patterning technology is innovatively employed for side-by-side demonstration of the exclusive influences of graphene coating on the solid-electrolyte interphase (SEI) formation and the structural stability of the SNC electrode. The silicon nanocone-graphene (SNC-G) electrode achieves a longer cycle life (1715 cycles), higher Coulombic efficiency (average 98.2%), better rate capability, and lower electrode polarization than the SNC electrode. The patterning of the graphene coating provides a much direct and convincing morphological comparison between the SNC-G structure and the SNC structure, showing clearly that the SNC-G area maintains a thin SEI layer and stable nanostructure after cycling, while the SNC area is gradually damaged and covered with a thick SEI layer after 100 cycles. Our results clearly indicate the improved electrochemical performance and interfacial stability attributed to the vertical graphene coating, and the as-proposed patterning technology also paves a new way for comparative research on coating materials for lithium-ion batteries.

Spontaneous construction of graphene on boron-doped diamond (111) surface has been found in first-principles calculations. Boron-doping-induced surface reconstruction is the mechanism responsible for the diamond-to-graphene phase transition. Furthermore, the effect on the surface is unexpectedly observed at any doping depth down to the 7th layer, and a low concentration of substituent boron – only ¼ – is effective for graphene formation. Amazingly, when boron atoms are incorporated into the fifth layer, the direct optimization of the 1 × 1 surface automatically gives rise to a graphene structure from the first bilayer with no energy barrier, indicating that the formation of graphene is spontaneous. These findings provide an alternative strategy for graphene synthesis on wide-gap insulators with high thermal conductivity.

Fabricating perfect plasmonic nanostructures has been a major challenge in surface enhanced Raman scattering (SERS) research. Here, a double-layer stacked Au/Al2O3@Au nanosphere structures is designed on the silicon wafer to bring high density, high intensity "hot spots" effect. A simply reproducible high-throughput approach is shown to fabricate feasibly this plasmonic nanostructures by rapid thermal annealing (RTA) and atomic layer deposition process (ALD). The double-layer stacked Au nanospheres construct a three-dimensional plasmonic nanostructure with tunable nanospacing and high-density nanojunctions between adjacent Au nanospheres by ultrathin Al2O3 isolation layer, producing highly strong plasmonic coupling so that the electromagnetic near-field is greatly enhanced to obtain a highly uniform increase of SERS with an enhancement factor (EF) of over 10(7). Both heterogeneous nanosphere group (Au/Al2O3@Ag) and pyramid-shaped arrays structure substrate can help to increase the SERS signals further, with a EF of nearly 10(9). These wafer-scale, high density homo/hetero-metal-nanosphere arrays with tunable nanojunction between adjacent shell-isolated nanospheres have significant implications for ultrasensitive Raman detection, molecular electronics, and nanophotonics.

We propose a simple and fast approach to prepare surface-enhanced Raman scattering (SERS) substrates over a large area with high flexibility by using direct laser writing (DLW) technique. The proposal is demonstrated by the direct fabrication of an array and a complex of symmetry-broken nanocorrals with DLW followed by a metal deposition process. SERS measurements show significant SERS enhancement, which can be controlled through engineering the focused “hot spots” by changing the structural parameters. The experimental observations are further confirmed by our simulations with a finite-difference time-domain tool. The studies can be extended to versatile SERS substrates with arbitrary geometries.

The porous anodic alumina membranes (PAAMs) have been successfully used as templates for the fabrication of functional nano-materials due to their outstanding regularity and physicochemical properties. In this paper, a transparent double-sided anodic alumina membrane with ultra-thin aluminum substrate was fabricated with the three-step anodic oxidation method in the oxalic acid electrolyte. The characters such as the top-surface morphology, membrane thickness, and depth of nanopores of this three-layer (Al2O3-Al-Al2O3) sandwiched nano-structure were controllable through regulating the main anodic oxidation conditions, e.g., anodic oxidation time of various steps, coating remove process. The experiments data revealed that the aluminum substrate is exponential declined with the oxidation time when it was approximately reduced by a few micrometers. This new double-sided anodic alumina membrane can be used as the high-quality functional field emission materials and templates.

A simple and universal templating approach is developed for fabricating large-scale ordered metallic nanocone arrays with high density (5 × 108 tips cm−2). A silicon nanocone array is prepared as the original template to form conical pits in a soft polymer template by thermal nanoimprinting. After metal deposition fills the pits, the resulting large-scale metallic nanocone array with sharp nanotips can be adhered to and peeled onto another polymer substrate by a simple, novel process. Avoiding the challenges of peeling from a hard template, a crucial baking process enables peeling, taking advantage of the difference in glass transition temperature (GTT) between the respective soft polymer materials of the deposition template and the transfer substrate. The method as a whole is designed for perfectible formation of a variety of metallic nanocone arrays. It provides a universally reliable shortcut to fabricate large-scale metallic nanocone arrays without lithography or etching steps, and it can be extended to the fabrication of other three-dimensional metallic-array nanostructures. Further, the as-formed Ag nanocone arrays show a large, stable surface enhancement for Raman scattering due to the nanofocused effect of the electromagnetic field induced by the conical nanostructures.

Three-dimensional (3D) nanostructures and nanodevices have attracted tremendous interest in the past few years due to their special mechanical and physical properties. Nanodevices using 3D nanostructures as the building blocks have been demonstrated to exhibit multifunctionality and functions that conventional planar devices cannot achieve. In this article, we report and review focused ion beam techniques for direct site-specific growth of 3D nanostructures and postgrowth shape modification of freestanding nanostructures by ion beam-induced chemical vapor deposition and ion-beam-irradiation-induced plastic bending, respectively. Such techniques have shown nanometer-scale resolution and accuracy in the fabrication of metallic nanoelectrodes, 3D pickup coils, nanogaps, and multibranched structures. Characterization of the resulting nanostructures shows that focused ion beam techniques allow conducting and superconducting freestanding 3D structures to be tailored in size, geometry, and integrated with planar electronic, mechanical, and superconducting nanodevices, potentially enabling lab-on-a-chip experiments.

Sub-5 nm metal nanogaps have attracted widespread attention in physics, chemistry, material sciences, and biology due to their physical properties, including great plasmon-enhanced effects in light-matter interactions and charge tunneling, Coulomb blockade, and the Kondo effect under an electrical stimulus. These properties especially meet the needs of many cutting-edge devices, such as sensing, optical, molecular, and electronic devices. However, fabricating sub-5 nm nanogaps is still challenging at the present, and scaled and reliable fabrication, improved addressability, and multifunction integration are desired for further applications in commercial devices. The aim of this work is to provide a comprehensive overview of sub-5 nm nanogaps and to present recent advancements in metal nanogaps, including their physical properties, fabrication methods, and device applications, with the ultimate aim to further inspire scientists and engineers in their research.

Here we report a method that enables the fabrication of hollow metallic pyramid plasmonic structures on free-standing copper grids, which were fabricated by direct laser writing lithography followed by noble metal deposition. Gratings on the faces of these pyramids can translate incident light into plasmons that propagate toward the apex of the noble metal coated pyramids. Surface Enhanced Raman Scattering (SERS) measurements confirm that these hollow metallic pyramid structures have superior properties to the planar metal surface and the degree of enhancement can be tuned by the size and geometry of the fabricated structures, which potentially could be used for better understanding of surface enhanced plasmonics on free-standing three dimensional structures as well as find application in the research field of SERS.

Single-walled carbon nanotubes (SWNTs) grown by chemical vapor deposition (CVD) are widely used for fabrication of high-performance nanotube devices. However, the high-temperature growth is incompatible with the current complementary metal-oxide semiconductor (CMOS) technology. We demonstrate a low-temperature and direct deposition of the CVD-grown SWNTs. The nanotubes are synthesized by floating catalytic CVD technique and further carried by the flowing gas directly to the low- temperature area. Individual SWNTs have been successfully deposited on Si/ SiO2 substrates covered with a polymethylmethacrylate layer, which results in a suspended geometry of the nanotube in the fabricated devices. We subsequently investigate the electrical-transport properties of a representative small band gap nanotube, which exhibits an ambipolar feature with p-channel mobility up to 1410 cm 2 V −1 S −1 at room temperature. Furthermore, low- temperature measurements down to 4 K reveal different transport characteristics with the gate voltage biased near zero or at a large negative value, respectively.

Large-area patterned boron carbide nanowires (B4C NWs) have been synthesized using chemical vapor deposition (CVD). The average diameter of B4C NWs is about 50 nm, with a mean length of 20 μm. The B4C NWs have a single-crystal structure and conductivities around 5.1 × 10−2 Ω−1·cm−1. Field emission measurements of patterned B4C NWs films show that their turn-on electric field is 2.7 V/μm, lower than that of continuous B4C NWs films. A single nanowire also exhibits excellent flexibility under high-strain bending cycles without deformation or failure. All together, this suggests that B4C NWs are a promising candidate for flexible cold cathode materials.

Three dimensional (3D) plasmonic nanostructure is perfect for the surface-enhanced Raman scattering (SERS) and also very suitable for surface catalytic reaction, but how to design and fabricate is still a robust task. Here, we show a 3D plasmonic nanohybrid of vertical graphene-nanosheet sandwiched by Ag-nanoparticles on the silicon nanocone array substrate for enhanced surface catalytic reaction. By SERS detection, we find that this hierarchical nanohybrid structure is highly efficient in the enhancement of catalytic reaction, even at a very low concentration of 10−11 M, which is far better than previous reports by four orders of magnitude. A strong electric field enhancement produced in the 3D framework nanohybrids of graphene nanosheet/Ag-nanoparticles is responsible for this great enhancement of catalytic reaction, due to larger electron collective oscillation in the composite system. Especially the oxygen adsorbed on the graphene and Ag nanoparticles can be excited to triplet excited states, and the electrons on the graphene and the nanoparticles can be effectively transferred to the oxygen, which plays very important role in molecular catalytic reactions. Our results demonstrate the contribution of graphene in plasmon-driven catalytic reactions, revealing a co-driven reaction process.This excellent SERS substrate can be used for future plasmon and graphene co-catalytic surface catalytic reactions, graphene-based surface plasmon sensors and so on.

Techniques for scalable fabrication of one-dimensional or quasi-one-dimensional nanowires are of great importance to observe quantum size effects and build quantum information devices. In this work, we developed a technique for size reduction of both lateral and freestanding tungsten composite nanostructures using focused-ion-beam (FIB) thinning. Different exposure times and ion-beam currents were used to control the final size and the thinning rate and accuracy of a group of nanowires, an individual nanowire and a portion of a nanowire by low-current site-specific milling. A transmission electron microscope image of a thinned superconducting tungsten composite nanowire with width reduced from 80nm to 50nm shows uniform shrinking along the length of the wire and high resolution image shows no obvious changes of the morphology after thinning. The variation of the superconducting critical current density upon thinning is insignificant; it is 1.7x10^5 and 1.4x10^5A/cm^2 at 4.26K for the as-deposited and wire with width reduced to 50nm, respectively. These results suggest that FIB-milling is a potential approach for controllable size reduction enabling the observation of size- and quantum effects.

It has been demonstrated that metamaterials play a very important role in plasmonic devices. The behavior of surface plasmon polaritons (SPPs) is highly related with the roughness of metal/dielectric interface, for instance, a smooth metal surface can largely elongate the propagation length of SPP. In this work, an improved template stripping method is developed to fabricate ultrasmooth metamaterials of nanoscale complementary split ring resonators (CSRRs). By using an ultraviolet photoresist of SU-8 as the adhesive, nanoscale metal CSRR structures with ultrasmooth surface were peeled off from silicon template by employing a combined process of pre-baking, UV irradiation and post-baking. By optimization of the pre-baking temperature and the depth of the nanopatterns, ultrasmooth nanoscale CSRRs with a gap of 30nm were obtained. Our results indicate that the approach of template stripping by implementation of an SU-8 adhesive layer is an effective method to produce elaborated hollow nanostructures with ultrasmooth surface and nanoscale gap, which may have potentials in sensing applications.

Freestanding nanostructures are fundamental elements to construct three-dimensional (3D) nanodevices. The bending of nanopillars by ion irradiation can be used to produce overhanging nanostructures. In this paper, we report the bending of focused-ion-beam (FIB) grown platinum nanopillars by FIB irradiation. The results show that for nanopillars originally perpendicular to the substrate, by adjusting the relative geometry of the incident ion beam and the nanopillars, desired bending direction and shape can be achieved. Such nanostructures can be used for 3D nanodevice constructions. Besides, ion irradiation with optimized conditions can be used to improve the surface morphology of the as-deposited nanopillars. Our results suggest that the method of bending freestanding nanoobjects using FIB is likely to be advantageous to construct interconnects in 3D nanostructures towards the properties investigations of selected individual nanoobjects.

A fast reactive ion etching (RIE) treatment method is presented for dramatic enhancement of the field emission performances of nanocrystalline diamond (NCD) films. In this method a moment RIE treatment is able to modify the surface morphologies of NCD films and form a large area of nanoneedle-like arrays on the NCD films, in which the diamond nanoparticles were seeded on the film to serve as an etching mask. These elaborated diamond nanoneedle-like structures showed good uniformity and dense morphology with a controllable aspect ratio and distribution density and thereby significantly increased the electron field emission properties of the NCD films due to the formation of more emitting tips and enhanced field enhancement factor.

Using focused ion beam etching technique, the authors fabricated a 28 atomic monolayers thick, 500 nm wide, and 10 μm long Pb nanobridge from an atomically flat Pb thin film grown on Si by molecular beam epitaxy. Electric transport measurements show exotic resistance oscillations in the superconducting state far below its critical field HC and cascading terraces near the superconducting transition region. Furthermore, the bridge shows an unusual semiconducting behavior above the superconducting transition temperature TC. The results are in contrast to those observed in its counterpart of the two-dimensional thin film.

Electrical conductivity, current-voltage (I-V) characteristics, and low-temperature magnetoresistance of template-synthesized poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires are reported. The room-temperature conductivity of the semiconducting nanowire with a diameter of 82 nm is about 80 S/cm. It is found that with lowering temperature, the I-V curves show a transition from linear to nonlinear around 50 K and a clear Coulomb-gap-like structure appears on the differential conductance (dl/dV) curves possibly due to enhanced electron-electron interaction. The resistance below 70 K is dependent on the applied bias voltage used in the resistance measurements due to the nonlinear I-V characteristics. The magnetoresistance below 10 K is positive and increases with lowering temperature due to the wavefunction shrinkage effect on hopping conduction. Copyright (C) 2009 John Wiley & Sons, Ltd.

We demonstrate the intrinsic memory function of ferroelectric field-effect transistors (FeFETs) based on an integration of individual single-walled carbon nanotubes (SWCNTs) and epitaxial ferroelectric films. In contrast to the previously reported "charge-storage" CNT-FET memories, whose operations are haunted by a lack of control over the "charge traps", the present CNT-FeFETs exhibit a well-defined memory hysteresis loop induced by the reversible remnant polarization of the ferroelectric films. Large memory windows approximately 4 V, data retention time up to 1 week, and ultralow power consumption (energy per bit) of femto-joule, are highlighted in this report. Further simulations and experimental results show that the memory device is valid under operation voltage less than 1 V due to an electric-field enhancement effect induced by the ultrathin SWCNTs.

The walls of magnetic domains can become trapped in a ferromagnetic metallic point contact when the thickness of the film and the width of the contact are less than their critical values 1 . The discovery that domain walls can be moved from such constrictions by a sufficiently large current has attracted considerable attention from researchers working on both fundamental research and potential applications 2‐12 . Here we show that Invar nanocontacts fabricated on silica substrates exhibit a sharp drop in resistance with increasing bias voltage at room temperature in the absence of an applied magnetic field. Moreover, when two nanocontacts are combined in an all-metallic comparison circuit, it is possible to perform logical NOT operations. The use of electrical currents rather than applied magnetic fields to control the domain walls also reduces energy consumption and the risk of crosstalk in devices 13,14 . We fabricated nanocontact structures on an Invar alloy film

Individual zinc oxide tetrapods were designed as multiterminal sensors by the e-beam lithography method. Different from double-terminal sensors, these sensors can give multiple responses to a single signal at the same time. The designed tetrapod devices were employed to detect light with different wavelength. The results indicate that they are remarkable optoelectronic devices, sensitive to ultraviolet light, and have advantages on distinguishing noises and increasing sensitivity. This should be helpful for weak signal measurements of nanodevices.

Single crystalline boron nanocones are obtained by a simple chemical vapor deposition method. Electric conductivity values of boron nanocones are (1.0-7.3) x 10(-5) (Omega cm)(-1). Results of field emission show the low turn-on and threshold electric fields of about 3.5 V mu m(-1) and 5.3 V mu m(-1), respectively. Boron nanocones with good electrical transport and field emission properties are promising candidates for application in flat panel displays and nanoelectronics building blocks.

The mechanical behaviors of microstructures and micro-devices have drawn the attention from researchers on materials and mechanics in recent years. To understand the rule of these behaviors, the deformation measurement techniques with micro/nanometer sensitivity and spatial resolution are required. In this paper, a micro-marker identification method is developed to measure microstructure deformation. The micro-markers were directly produced on the top surface of microstructures by taking advantage of ion milling of focused ion beam (FIB) system. Based on the analysis of marker images captured by electronic microscope with specific correlation software, the deformation information in microstructures can be easily obtained. The principle of the technique is introduced in detail in the paper. An example experiment was executed to measure the displacement and strain distribution in a MEMS device. Obtained results show that the technique can be well applied to the deformation measurement of the micro/nano-electro-mechanical-systems (MEMS/NEMS).

Based on a methanol-thermal reaction method, coating carbon nanotubes (CNTs) with needle-like iron oxide has been achieved. The structure, composition and morphology of the coatings were characterized by using transmission electron microscopy, X-ray energy dispersive spectrum and X-ray photoelectron spectroscopy. The experimental results indicate that the pre-oxidation of CNTs and the acid-based methanol-thermal environment are very important points to obtain dense and uniform coatings on CNTs. Magnetic measurement for the iron oxide coatings indicates that the coercivity has been enhanced after coating.

Freestanding three-dimensional nanostructures have attracted intense attention for their potential application in novel electronic, optical, magnetic, biological and mechanical devices. However, controlled fabrication of highly-ordered, well-shaped and freestanding core-shell hetero-structures in large scale cost-effectively is still a challenge. Here we present the constructing of freestanding hetero-structures by taking advantages of lateral re-deposition, a phenomenon that occurred during plasma-matter interaction and usually to be minimized/avoided in conventional device fabrication. Various freestanding nanowires were irradiated under optimized conditions, in that upon etching, the sputtered species from the supporting substrates are re-deposited laterally onto the core material, mainly through plasma-phase interaction to form complex core-shell structures. Factors, including the supporting substrate, plasma power, irradiation time and gas flow rate, were used to tune the properties of the desired structures. Pencil-like, conic and wing-shape free-standing hetero-structures have been formed with controllable growth rate of sub-nanometer per minute across the width of the structure. The related mechanism was proposed. Our results indicate that such technique might be a potential approach for the fabrication of high aspect-ratio freestanding functional core-shell structures to construct mechanical, optical, biological and electrical devices.

Thickness, homogeneity and coverage of the surface passivation layer on Si anodes for Li-ion batteries have decisive influences on their cyclic performance and coulombic efficiency, but related information is difficult to obtain, especially during cycling. In this work, a well-defined silicon nanocone (SNC) on silicon wafer sample has been fabricated as a model electrode in lithium ion batteries to investigate the growth of surface species on the SNC electrode during cycling using ex situ scanning electronic microscopy. It is observed that an extra 5 μm thick layer covers the top of the SNCs after 25 cycles at 0.1 C. This top layer has been proven to be a solid electrolyte interphase (SEI) layer by designing a solid lithium battery. It is noticed that the SEI layer is much thinner at a high rate of 1 C. The cyclic performance of the SNCs at 1 C looks much better than that of the same electrode at 0.1 C in the half cell. Our findings clearly demonstrate that the formation of the thick SEI on the naked nanostructured Si anode during low rate cycling is a serious problem for practical applications. An in depth understanding of this problem may provide valuable guidance in designing Si-based anode materials.

Single grain boundary junctions are used for the fabrication of suspended nanogap electrodes with a gapwidth down to 1-2 nm through the break of such junctions by focused ion beam (FIB) milling. With advantages of stability and no debris, such nanogap electrodes are suitable for single molecular electronic device construction.

Conductivity and magnetoresistance (MR) measurements on pellets of conducting polyaniline and polypyrrole nanotubes/wires are presented. A transition from small negative MR to large positive MR was measured below 60 K. The positive and negative MR has been discussed in terms of a wavefunction shrinkage effect and a quantum interference effect on hopping conduction. In addition, further studies show that the MR of single polymer nanotubes/wires is very small even at 2 K (MR < 5% at 10 T) compared with that of the pellets (40%-100% at 10 T), and no evident and stable negative MR is observed above 50 K. The results indicate that the MR in the bulk pellet samples made of polymer nanotubes/wires is dominated by a random network of inter-fibril contacts.