Environmental Transmission Electron Microscopy in Nanotechnology

Abstract

We have shown that ETEM is a valuable technique for understanding the response of nanoparticle systems to a gaseous environmentat near atomic-level. The modern ETEM allows the dynamic behavior of the nanoparticles to be studied in real time with atomic-resolutionimaging and electron diffraction in up to 50 Torr of gas pressure. On a machine equipped with a field-emission gun, electronenergy-loss spectra can be recorded using a sub-nanometer probe so that elemental and electronic structural changes occurringin individual nanoparticles can be followed in situ. This powerful combination of in-situ imaging, diffraction and spectroscopy provides detailed information about gas-solid phase transformation mechanisms in individualnanoparticles. Quantitative measurements can be used to derive reaction rates and activation energies from very small areasand should allow full reaction kinetics to be determined as a function of nanoparticles size. The ETEM can also be used toperform in-situ synthesis of nanophase materials. The simultaneous characterization can be performed during synthesis allowing synthesisconditions to be varied and optimized rapidly. Sub-nanometer electron probes can also permit nano-lithographic structuresto be deposited and studied under a wide variety of different conditions.