Further information
Stephen J. Pennycook, ORNL Corporate Fellow, Electron Microscopy Group Leader, Materials Science and Technology Division, Oak Ridge National Laboratory presents this lecture.
Abstract: In recent years the probe size in the scanning transmission electron microscope has decreased more than a factor of two, bringing improved resolution not only laterally but also vertically, allowing defects and even single atoms to be located inside materials in three dimensions. Examples will include mapping of individual Hf atoms inside the gate oxide of a Si/SiO2/HfO2 device structure, and the imaging of Au interstitials inside Si nanowires that match well in both atomic position and relative formation energies with density functional calculations. Single atom sensitivity has also been achieved in electron energy loss spectroscopy, which can not only positively identify the element, but also, from the fine structure, provide information on local bonding, band structure and carrier concentration. Several examples will be shown of oxide materials and heterostructures where spectroscopic analysis reveals the origin of surprising bulk properties including ferromagnetism in Co-doped anatase and collosal ionic conductivity in Y-stabilized ZrO2/SrTiO3 heterostructures.
This research was sponsored by the Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, US Department of Energy and NSF/ECS No. 0224138