We report that the substrate-free gas-phase graphene synthesis method produces clean and highly ordered graphene sheets that are similar in quality to the graphene obtained through the mechanical exfoliation of highly oriented pyrolytic graphite.

The strong interaction of electrons with small volumes of matter make them an ideal probe for nanomaterials, but our ability to fully use this signal in electron microscopes remains limited by lens aberrations. To bring this unique advantage to bear on materials research requires a sample space for electron scattering experiments in a tunable electron-optical environment. This is the vision for the Transmission Electron Aberration-corrected Microscope (TEAM) project, which was initiated as a collaborative effort to re-design the electron microscope around aberration-correcting optics. The resulting improvements in spatial, spectral and temporal resolution, the increased space around the sample and the possibility of exotic electron-optical settings will enable new types of experiments. This contribution will give an overview of the TEAM project and its current status, illustrate the performance of the TEAM 0.5 instrument, with highlights from early applications of the machine, and outline future scientific opportunities for aberration-corrected microscopy.

A growing number of atomic force microscope (AFM) applications make use of metal-coated probes. Probe metallization can cause adverse side-effects and disadvantages such as stress-induced cantilever bending, thermal expansion mismatch, increased tip radius and limited device lifetime due to coating wear. In this study we demonstrate how to overcome these limitations using microstructural design to create a metallic glass thin film alloy, from which monostructural all-metal AFM cantilevers are fabricated. A detailed compositional study of co-sputtered Cu-Hf films is performed using x-ray diffraction (XRD), nanoindentation, four-point probe and in situ multi-beam optical stress sensing (MOSS). Metallic glass Cu(90)Hf(10) films are found to possess an optimal combination of electrical resistivity (96 microOmega cm), nanoindentation hardness (5.2 GPa), ductility and incremental stress. A continuum model is developed which uses measured MOSS data to predict cantilever warping caused by stress gradients generated during film growth. Subsequently, a microfabrication process is developed to create Cu(90)Hf(10) AFM probes. Uncurled, 1 microm thick cantilevers having lengths of 100-400 microm are fabricated, with tip radii ranging from 10 to 40 nm. As a proof of principle, these all-metal Cu-Hf AFM probes are mounted in a commercial AFM and used to successfully image a known test structure.

Direct imaging of surface molecules and the interfaces between soft and hard materials on functionalized nanoparticles is a great challenge using modern microscopy techniques. We show that graphene, a single atomic layer of sp(2)-bonded carbon atoms, can be employed as an ultrathin support film that enables direct imaging of molecular layers and interfaces in both conventional and atomic-resolution transmission electron microscopy. An atomic-resolution imaging study of the capping layers and interfaces of citrate-stabilized gold nanoparticles is used to demonstrate this novel capability. Our findings reveal the unique potential of graphene as an ideal support film for atomic-resolution transmission electron microscopy of hard and soft nanomaterials.

The hydrogen oxidation reaction (HOR) was studied at the home made TiO(x)-Pt/C nanocatalysts in 0.5 mol dm(-3) HClO(4) at 25 degrees C. Pt/C catalyst was first synthesized by modified ethylene glycol method (EG) on commercially used carbon support (Vulcan XC-72). Then TiO(x)-Pt/C catalyst was prepared by the polyole method followed by TiO(x) post-deposition. The synthesized catalyst was characterized by XRD, TEM and EDX techniques. It was found that Pt/C catalyst nanoparticles were homogenously distributed over carbon support with the mean particle size of about 2.4 nm. The quite similar, homogenous distribution and particle size were obtained for Pt/C doped by TiO(x) catalyst which was the confirmation that TiO(x) post-deposition did not lead to significant growth of the Pt nanoparticles. The electrochemically active surface area of the catalyst was determined by using the cyclic voltammetry technique.The kinetics of hydrogen oxidation was investigated by the linear sweep voltammetry technique at the rotating disc electrode (RDE). The kinetic equations used for the analysis were derived considering the reversible or irreversible nature of the kinetics of the HOR. It was found that the hydrogen oxidation reaction for an investigated catalyst proceeded as an electrochemically reversible reaction. The values determined for the kinetic parameters-Tafel slope of 28 mV dec(-1) and exchange current density about 0.4 mA cm(-2)(Pt) are in good agreement with usually reported values for a hydrogen oxidation reaction with platinum catalysts in acid solutions.

We describe a setup for the resonance frequency measurement of individual microcantilevers. The setup displays both high spatial selectivity and sensitivity to specimen vibrations by utilizing a tapered fiber tip. The high sensitivity to specimen vibrations is achieved by the combination of optical Fabry-Perot interferometry and narrow band rf detection. Wave fronts reflected on the specimen and on the fiber tip end face interfere, thus no reference plane on the specimen is needed, as demonstrated with the example of freestanding silicon nitride microcantilevers. The resulting system is integrated in a DB-235 dual beam focused ion beam (FIB) system, thereby allowing the measurement of microcantilever responses during observation in scanning electron microscopy mode. The FIB was used to modify the optical fiber tip. At this point of our rf system development, the microcantilevers used to characterize the detector were not modified in situ.

The ability of electron microscopes to analyze all the atoms in individual nanostructures is limited by lens aberrations. However, recent advances in aberration-correcting electron optics have led to greatly enhanced instrument performance and new techniques of electron microscopy. The development of an ultrastable electron microscope with aberration-correcting optics and a monochromated high-brightness source has significantly improved instrument resolution and contrast. In the present work, we report information transfer beyond 50 pm and show images of single gold atoms with a signal-to-noise ratio as large as 10. The instrument's new capabilities were exploited to detect a buried Sigma3 {112} grain boundary and observe the dynamic arrangements of single atoms and atom pairs with sub-angstrom resolution. These results mark an important step toward meeting the challenge of determining the three-dimensional atomic-scale structure of nanomaterials.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 - August 7, 2008.

We present a novel method for synthesizing graphene sheets in the gas phase using a substrate-free, atmospheric-pressure microwave plasma reactor. Graphene sheets were synthesized by passing liquid ethanol droplets into an argon plasma. The graphene sheets were characterized by transmission electron microscopy, electron energy loss spectroscopy, Raman spectroscopy, and electron diffraction. We prove that graphene can be created without three-dimensional materials or substrates and demonstrate a possible avenue to the large-scale synthesis of graphene.

A novel reconstruction procedure is proposed to achieve atomic resolution in electron tomography. The method exploits the fact that crystals are discrete assemblies of atoms (atomicity). This constraint enables us to obtain a three-dimensional (3-D) reconstruction of test structures from less than 10 projections even in the presence of noise and defects. Phase contrast transmission electron microscopy (TEM) images of a gold nanocrystal were simulated in six different zone axes. The discrete number of atoms in every column is determined by application of the channelling theory to reconstructed electron exit waves. The procedure is experimentally validated by experiments with gold samples. Our results show that discrete tomography recovers the shape of the particle as well as the position of its 309 atoms from only three projections. Experiments on a nanocrystal that contains several missing atoms, both on the surface and in the core of the nanocrystal, while considering a high noise level in each simulated image were performed to prove the stability of the approach to reconstruct defects. The algorithm is well capable of handling structural defects in a highly noisy environment, even if this causes atom count "errors" in the projection data.