Single nanometre-sized pores (nanopores) embedded in an insulating membrane are an exciting new class of nanosensors for rapid electrical detection and characterization of biomolecules. Notable examples include alpha-hemolysin protein nanopores in lipid membranes and solid-state nanopores in Si3N4. Here we report a new technique for fabricating silicon oxide nanopores with single-nanometre precision and direct visual feedback, using state-of-the-art silicon technology and transmission electron microscopy. First, a pore of 20 nm is opened in a silicon membrane by using electron-beam lithography and anisotropic etching. After thermal oxidation, the pore can be reduced to a single-nanometre when it is exposed to a high-energy electron beam. This fluidizes the silicon oxide leading to a shrinking of the small hole due to surface tension. When the electron beam is switched off, the material quenches and retains its shape. This technique dramatically increases the level of control in the fabrication of a wide range of nanodevices.

of these junctions by chemical functionalization (23) or physical processing can markedly increase the TCR as shown in the annealing experiment ( fig. S3). The presence of intertube junctions dramatically decreases the efficiency of heat transport along the SWNT film, thereby thermally insulating the sensitive element from the supporting substrate, which enhances the temperature response (18). Optimization of the room-temperature performance of the SWNT-based bolometer may provide a cost-efficient alternative to pyroelectric detectors, vanadium dioxide, and amorphous silicon-based bolometer arrays (18).The SWNT networks used here are a mixture of semiconducting and metallic SWNTs; metallic pathways present within such networks reduce the temperature dependence of the resistance (23). The ultimate enhancement of the TCR would be achieved by the exclusive use of semiconducting SWNTs, but even with current preparations, the implementation outlined above in conjunction with recent advances in carbon nanotube thin film preparation technology (3, 7, 22,27,28) allows the manufacture of high-density 2D arrays of SWNT bolometers that are suitable for applications in thermal imaging, spectroscopy, and infrared astronomy (18).References and Notes 1. J. A. Misewich et al., Science 300, 783 (2003). 2. M. Freitag et al., Phys. Rev. Lett. 93, 076803 (2004 Atomic-resolution electron microscopy reveals that pillarlike silicon double columns exist in the hardening nanoprecipitates of AlMgSi alloys, which vary in structure and composition. Upon annealing, the Si 2 pillars provide the skeleton for the nanoparticles to evolve in composition, structure, and morphology. We show that they begin as tiny nuclei with a composition close to Mg 2 Si 2 Al 7 and a minimal mismatch with the aluminum matrix. They subsequently undergo a onedimensional growth in association with compositional change, becoming elongated particles. During the evolution toward the final Mg 5 Si 6 particles, the compositional change is accompanied by a characteristic structural change. Our study explains the nanoscopic reasons that the alloys make excellent automotive materials.A luminum is essential to modern civilizations because of its light weight, strength, and workability. Its many applications include fuel-efficient transportation vehicles (e.g., it comprises about 80% of a commercial aircraft_s unloaded weight), building construction, and food packaging. Pure aluminum is soft and has little strength or resistance to plastic deformation. However, alloyed with small amounts of other elements, it can provide the strength of steel at only half the weight. With thermal treatments, the added alloying elements can form nanometer-sized precipitates, which act as obstacles to dislocation movement in the crystal (atomic matrix), strengthening the aluminum. This phenomenon is known as precipitation hardening, and the hardening nanoprecipitates are named GP zones after the pioneer work by Guinier and Preston on AlCu alloys (1, 2).AlMgSi accounts for a large percentage of...

Al-Mg-Si nanoclusters embedded in aluminum transform through a delicate interplay of two characteristically distinct phase transformations: a diffusion-controlled substitutional transformation associated with solute enrichment and a swift displacive transformation involving collective shifts of columns of atoms once a critical enrichment has been reached. Through first-principles calculations, we show that these transformations are inseparable. Moreover, we show in atomistic detail how precipitates that are not superstructures of the matrix form from a supersaturated solid solution.

Since the successful correction of the spherical aberration (Cs) of the objective lens in a Philips CM 200 FEG ST microscope achieved by Rose and Haider et al [1][2], a few theoretical and computational expectations have been made to show the possible atomic imaging conditions in the Cs-corrected high-resolution transmission electron microscopy (HRTEM) [3][4]. These conditions include the phase-contrast imaging at a small defocus, the amplitude-contrast imaging at about zero defocus and the projected charge density (PCD) contrast imaging at a small over-focus. Meanwhile still some controversial opinions do exist concerning whether or not through-focus exit-wave function reconstruction (EWR) [5] and Cs-corrected HRTEM are complementary or exclusive. Up till now no systematic experimental and theoretical investigations on these issues have been carried out and therefore the theories about the optimum imaging conditions and the image interpretation remain to be either justified or established.In the present work, we conducted a systematic experimental investigation on the image regime of the new microscope, aiming to achieve the highest resolution directly in interpretable atomic images. Atomic images of a 0.136 nm resolution, which was the measured information limit of the microscope, have been obtained in different imaging ways. We also performed through-focus EWR, showing that in this microscope a posteriori correction of the exit-wave for aberrations is greatly simplified and therefore it is a microscope very convenient for users to reconstruct the exit-wave functions. Using the advantages of the Cs-corrected HRTEM, structural details of some solute atomic clusters in an Al-Mg-Si-Cu alloy system were successfully studied.In this microscope, a double hexapole corrector system is implemented to compensate the Cs of the objective lens and at the same time to suppress all the other aberration coefficients of whole the resulting system to the values below their maxima allowed. Owing to its special structure, the microscope requires an additional alignment procedure besides the basic alignment of the microscope. After the proper alignment, the microscope has a Cs value close to zero. We have taken through-focus series of high-resolution images from Si[110] specimens for varying specimen thickness. The obtained images were analyzed with image simulation and image processing.In this novel TEM we are able to obtain Si[110] atomic images of 0.136nm resolution in different imaging regimes. For conventional phase-contrast imaging, silicon black atom dumbbells are observed. For the amplitude-contrast, or more accurately, channeling-contrast imaging, atomic column positions in the images are indicated by the intensity maxima due to the electron channeling effect along columns. In the wave function reconstructed from through-focus image series taken from very thin specimens, the phases are linearly proportional to the projected potentials of atomic columns. Some of these ultra-high resolution images are shown in Fig.1a-d. It i...