Atomic resolution nanofabrication and dynamic characterization

Abstract

Summary form only given. Experiments on individual nanoparticles are generally difficult but can be carried out by the techniques of modern in-situ electron microscopy. With the continuous improvement of in situ techniques inside transmission electron microscope (TEM), the capabilities of TEM extend beyond structural characterization to high-precision nanofabrication and property measurement, which not only enriches the experimental methods of nanoresearch, but also provides new opportunities for the development in nanoscience and nanotechnology. Based on the idea of “setting up a nanolab inside a TEM”, we review our recent progress in atomic resolution nanofabrication and dynamic characterization of structure and properties of nanomaterials. The electron beam can be used as a tool to induce nanofabrication on an atomic scale. Selective irradiation of MWNTs with a focused electron beam can induce changes of their shape such as cutting, bending, welding and drilling a hole on them. In addition, metal crystals can be encapsulated inside graphitic nanocontainers that were designed for in-situ electron irradiation experiments. Under irradiation, the carbon shells contract and lead to compressive forces. By measuring the lattice spacings in HRTEM images of metal crystals inside graphitic shells, pressures on the order 10-20 GPa were determined. Non-hydrostatic pressure, e.g., inside collapsing nanotubes, may deform the crystals considerably. This can be used for studying the deformation behaviour of individual nanometer-sized crystals. Fig. 1 shows how a Co wire inside a carbon nanotube is deformed and extruded when the the nanotube collapses locally under electron irradiation. Another deformation cell, allowing the detailed study of crystal deformation, was designed by electron-beam structuring, as shown in Fig. 2. A 'carbon onion', encapsulating a Au crystal, was punctured by a fully focused electron beam and subsequently exposed to uniform irradiation so that the Au crystal was slowly extruded through the hole. The interaction between metal and carbon was also studied on an atomic scale by introducing Au and Pt atoms into graphene layers. Individual Au or Pt atoms were observed by HRTEM at different temperatures and their migration was monitored. Fig. 3 shows drilling a Snm-diameter hole by electron beam on graphene for third-generation gene sequencing. The mechanism of electron-beam induced high-resolution nanofabrication was also discussed.