[en] Nanostructured materials possess interesting physical and chemical properties which may differ significantly from their macroscopic counterparts. Understanding the size and shape dependence of nanostructures is important to the rational design of nanomaterials with a desired functionality. Scanning probe microscopy and its derivatives provide unique opportunities to deepen our insight into the electrical characteristics of nanostructures. We have developed several new approaches based on electric force microscopy that enable quantitative characterization of the electrical properties of nanostructured materials. Some example applications include the measurement of the characteristic capacitance of the EFM tip, the surface charge density of materials, and the charge carrier density in graphene and ultrathin organic films. (authors)

[en] Nanofabrication on insulating and flexible films of polydimethylsiloxane (PDMS) using a focused ion beam (FIB) has been illustrated in this study. The charge accumulation effect, which is inevitable in polymeric fabrication, was shown to be relieved by simultaneously introducing electron beam flooding in the area exposed to FIB. The topography of the fabricated pattern is subsequently characterized by using an atomic force microscope (AFM), by which the dependence of height/depth of the fabricated arrays on ion beam dose could be obtained. In addition, the swelling effect and milling effect relating to focused ion beam dose could be identified in this study.

[en] A large-scale molecular dynamics simulation was performed on the microstructure evolutions of Ca₇Mg₃ alloy during rapid cooling process. The structural evolution was analyzed by using the HA bond-type index method and the largest standard cluster analysis method. The validity of the simulation was confirmed by comparing the simulated structure factor S(q) with the experimental one. Results indicate that the simulated S(q) is well agreed with the experimental one. Results also demonstrate that the glass transition temperature is at about 580 K at the cooling rate of 1 × 10¹³ K/s; and the LSCs of [12/555] and [2/433 2/544 8/555] play an important role in the glass transition. These findings can improve the understanding of glass transition of liquid alloy under rapid cooling. (paper)

[en] Atomic force microscopy (AFM) is one of the key techniques for real-space imaging and structure characterization at the micro- and nanometer scale, and many remarkable new functions and techniques have been developed in recent years. Two special areas will be presented here: the various detection modes of AFM and their applications in the nanoscale research and measurement of physical properties, and the development of AFM techniques and their applications in basic and applied science. A brief comment will also be given on the further development of AFM probe techniques and their expanding application areas. (authors)

[en] Objective: To explore the imaging features of chest radiography and CT in patients with avian influenza A (H7N9). Methods: The imaging data of chest radiography and CT in 4 patients with H7N9 confirmed by real-time RT-PCR assay were retrospectively analyzed. All patients had chest radiography at first and 3 underwent CT examination, 3 had follow-up radiography. Results: Chest radiographs showed increased lung markings with pulmonary consolidation and interstitial change in 4 cases and consolidations were bilaterally distributed in 3 cases. The imaging appearances changed quickly during the follow-up. The bilateral consolidations, multiple ground-glass opacities, pleural effusion, hilar and mediastinal lymphadenopathy were found on CT. Conclusions: Avian influenza A (H7N9) has certain imaging features on chest radiography and CT, which is similar to those of H1N1 influenza. The final diagnosis of the avian influenza A (H7N9) depends on epidemiology and laboratory test. (authors)

[en] Friction measurement via atomic force microscope (AFM) relies on accurate calibration for the torsional spring constant of the AFM cantilever and its lateral deflection sensitivity. Here we describe a method that employs a suspended nanowire (SNW) as a reference beam to quantify the torsional spring constant of AFM cantilevers. Based on the fact that a uniform SNW with cylindrical symmetry has an identical spring constant when bent in any direction perpendicular to its axis, the spring constant of the SNW in a normal direction is determined by an AFM cantilever with a known normal spring constant, and is subsequently used as a force transfer standard to calibrate the torsional spring constant of the AFM cantilever. The lateral deflection sensitivity can be accurately measured by pushing the AFM tip laterally on the groove edge. The calibration result is compared to the well-known diamagnetic lateral force calibrator method and shows an uncertainty of 15% or better. The presented method is applicable for the lateral force calibration of AFM cantilevers in a wide range of instruments including inverted configurations and in an ultrahigh vacuum. (paper)

[en] The lateral resolution (LR) and signal-to-noise ratio (SNR) are the essential factors in the applications of scanning probe microscopy in quantitative measurement of surface charge distribution, potential profile, and dielectric properties. We use a model system to comprise Au nanoparticles (NPs) embedded in a polystyrene (PS) matrix to study the effects of various experimental parameters, such as modulation bias voltage, tip-sample distance, and actual tip shape, on the electrostatic interactions between the tips and samples. The results show that LR and SNR decrease when the tip-sample distance increases, while SNR increases with tip modulation voltage. LR is less sensitive to tip modulation voltage, but shows complex dependence on the sample geometric structure. In combination with a numerical simulation based on the integral capacitance model, the electrostatic force interaction between tip and sample was quantitatively analyzed. (authors)

[en] Field-emitted, low-energy electrons from the conducting tip of an atomic force microscope were adopted for nanolithography on calixarene ultrathin films coated on silicon wafers. A structural evolution from protrusion to depression down to a 30 nm spatial resolution was reproducibly obtained by tuning the sample voltage and exposure current in the lithography process. Close analyses of the profiles showed that the nanostructures formed by a single exposure with a high current are almost identical to those created by cumulative exposure with a lower current but an equal number of injected electrons. Surface potential imaging by Kelvin probe force microscopy found a negatively charged region surrounding the groove structures once the structures were formed. We conclude that the mechanism related to the formation of a temporary negative state and molecule decomposition, rather than thermal ablation, is responsible for the low-energy field-emission electron lithography on a calixarene molecular resist. We hope that our elucidation of the underlying mechanism is helpful for molecular resist design and further improving the reproducibility and throughput of nanolithography. (paper)

[en] Photodetectors based on α-phase In₂Se₃ ultrathin films demonstrate unusually high photoresponsivity comparing to those based on other two-dimensional (2D) materials, such as MoS₂. To understand the underlying mechanism, we investigate the ultrafast dynamics of In₂Se₃ ultrathin films ranging from 11 nm to 40 nm on mica and Au substrates, respectively, analogous to the practical layout of a photodetector. Our results show that the carrier lifetime of α-phase In₂Se₃ on mica is nearly independent of thickness and comparable to that of MoS₂, and the efficient charge carrier separation occurs on Au substrate. Because all of the key parameters of In₂Se₃ nanoflakes that determine its photoresponsive behavior are of similar values to those of MoS₂, we suggest that the interface effect, i.e. photogating effect and contact resistance, should be responsible for the dramatic photoresponsivity reported for field-effect transistor-type optoelectronic devices. (paper)