[en] Nanostructured diamond films are deposited on mirror-polished silicon wafers under continuous ion bombardment by using a hot-filament chemical vapor deposition (HFCVD) chamber equipped with a substrate bias system. The morphology and phase purity of the diamond film, as related to the different deposition parameters, are evaluated by scanning electron microscopy (SEM) and Raman scattering spectroscopy. The results show that nanostructured diamond films with a large area, low stress and smooth surface can be synthesized on mirror-polished Si substrates by an economical HFCVD method, and the size of diamond clusters in the film can be controlled by a suitable selection of deposition parameters such as the bias current density and the ratio of CH₄ to H₂. Furthermore, the relationship between the film's stress and the diamond clusters' size for the films synthesized under various parameters is revealed. The measurement of field emission from an as-grown nanostructured diamond film shows properties of a low emission threshold and a stable high-emission current density

[en] Free-space nanostructures are the fundamental building blocks of three-dimensional (3D) nanodevices with multi-functionality beyond that achievable by planar devices. Here we developed a reliable technique for the site-specific post-growth geometrical manipulation of freestanding superconducting nanowires using ion-beam irradiation with nanometer-scale resolution to fabricate uniformly shaped and sized clean-surface 3D nanostructures. Such structures could integrate with conventional superconducting quantum interference devices to detect magnetic fields both parallel and normal to the substrate. Property characterizations suggest that our focused-ion-beam technique allows tailoring of freestanding superconducting loops for size and geometry, potentially for lab-on-chip experiments.

[en] We report the results of angle dependent resistivity of NdFeAsO_0.82F_0.18 single crystals in the superconducting state. By doing the scaling of resistivity within the frame of the anisotropic Ginzburg-Landau theory, it is found that the angle dependent resistivity measured under different magnetic fields at a certain temperature can be collapsed onto one curve. As a scaling parameter, the anisotropy Γ can be determined for different temperatures. It is found that Γ(T) increases slowly with decreasing temperature, varying from Γ ≅ 5.48 at T = 50 K to Γ ≅ 6.24 at T = 44 K. This temperature dependence can be understood within the picture of multi-band superconductivity

[en] A measuring system for mechanical characterization of thin films based on a compact in situ micro-tensile tester and scanning electron microscope (SEM) moiré method is proposed. The load is exerted by the tensile tester and the full field strain is measured by SEM moiré method. The configuration of the tensile tester and the principle of SEM moiré method are introduced. In the tensile tester, a lever structure is designed to amplify the displacement imposed by lead–zirconate–titanate (PZT) actuator. The SEM moiré method is applied to measure the strain of the thin film, including both the average strain in the gage section and the local strain distribution at a specific region. As an application, the measuring system is applied to characterize the mechanical property of the free-standing aluminum thin film. The experimental results demonstrate the feasibility of the system and its good application potential for mechanical behavior analysis of film-like materials. (paper)

[en] B-doped ultrananocrystalline diamond (UNCD) films are grown using hot-filament chemical vapor deposition method, and their electrical transport properties varying with temperature are investigated. When the B-doped concentration of UNCD film is low, a step-like increase feature of the resistance is observed with decreasing temperature, reflecting at least three temperature-modified electronic state densities at the Fermi level according to three-dimensional Mott's variable range hopping transport mechanism, which is very different from that of reported B-doped nanodiamond. With increasing B-doped concentration, a superconductive transformation occurs in the UNCD film and the highest transformation temperature of 5.3 K is observed, which is higher than that reported for superconducting nanodiamond films. In addition, the superconducting coherence length is about 0.63 nm, which breaks a reported theoretical and experimental prediction about ultra-nanoscale diamond's superconductivity

[en] Vertically aligned single-crystal SnO₂ nanoshuttle arrays with uniform morphology and a relatively high aspect ratio were synthesized by a simple hot-wall chemical vapor deposition (CVD) method. It was found that regulating the growth temperature gradient could change the shape of the SnO₂ nanostructure from nanoshuttles to nanochisels and nanoneedles, and a self-catalyzing growth process was responsible for tunable morphologies of SnO₂ nanostructures. The as-synthesized SnO₂ nanoshuttles showed ultrahigh flexibility and strong toughness with a large elastic strain of ∼ 6.2, which is much higher than reported for Si and ZnO nanowire as well as most crystalline metallic materials. The field emitter fabricated using SnO₂ nanoshuttle arrays has a low turn-on electric field of around 0.6 V µm⁻¹, and a high field emission current density of above 10 mA cm⁻², which is comparable with the highest emission current density of carbon nanotube and nanowire field emitters.

[en] A novel approach based on the Poisson spot effect in a conventional optical lithography system is presented for fabricating large-scale ordered ring patterns at low cost, in which the pattern geometries are tuned by controlling the exposure dose and deliberate design of the mask patterns. Following this by cryogenic deep etching, the ring patterns are transferred into Si substrates, resulting in various vertical tubular Si array structures. Microscopic analysis indicates that the as-fabricated Si microtubes have smooth interior and exterior surfaces that are uniform in size, shape and wall-thickness, which exhibit potential applications as electronic, biological and medical devices.

[en] The spatially continuous control of the physical properties in semiconductor materials is an important strategy in increasing electron-capturing or light-harvesting efficiencies, which is highly desirable for the application of optoelectronic devices including photodetectors, solar cells and biosensors. Unlike the multi-layer growth of chemical composition modulation, local strain offers a convenient way to continuously tune the physical properties of a single semiconductor layer, and open up new possibility for band engineering within the 2D plane. Here, we demonstrate that the gradient refractive index and bandgap can be generated in atomically thin transition metal dichalcogenide flakes due to the effect of thermal strain difference. A highly resolved confocal scanning optical microscopy is used to perform a real-space light-reflection mapping of suspended atomically thin WSe₂ flakes at the low temperature of 4.2 K, in which the parabolic light-reflection profiles have been observed on suspended monolayer and bilayer WSe₂ flakes. This finding is corroborated by our theoretical model which includes the effect of strain on both the refractive index and bandgap of nanostructures. The inhomogeneous local strain observed here will allow new device functionalities to be integrated within 2D layered materials, such as in-plane photodetectors and photovoltaic devices. (paper)

[en] Nb/Al–AlO_x/Nb tunnel junctions are often used in the studies of macroscopic quantum phenomena and superconducting qubit applications of the Josephson devices. In this work, we describe a convenient and reliable process using electron beam lithography for the fabrication of high-quality, submicron-sized Nb/Al–AlO_x/Nb Josephson junctions. The technique follows the well-known selective Nb etching process and produces high-quality junctions with V_m = 100 mV at 2.3 K for the typical critical current density of 2.2 kA/cm², which can be adjusted by controlling the oxygen pressure and oxidation time during the formation of the tunnelling barrier. We present the results of the temperature dependence of the sub-gap current and in-plane magnetic-field dependence of the critical current, and compare them with the theoretical predictions. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] High-quality continuous uniform monolayer graphene was grown on polycrystalline PtRh_2_0 alloy foils by low pressure chemical vapor deposition. The morphology of graphene was investigated by Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. Analysis results confirm that high quality single-layer graphene was fabricated on PtRh_2_0 foil at 1050 °C using a lower flux of methane under low pressure. Graphene films were transferred onto the SiO_2/Si substrate by the bubbling transfer method. The mobility of a test field effect transistor made of the graphene grown on PtRh_2_0 was measured and reckoned at room temperature, showing that the carrier mobility was about 4000 cm"2 V"−"1 s"−"1. The results indicate that desired quality of single-layer graphene grown on PtRh_2_0 foils can be obtained by tuning reaction conditions