UHV-HREM and diffraction of surfaces

Characterization of the structure of surfaces is very important in order to develop a fundamental understanding of the electronic, mechanical and chemical properties of a material. While transmission electron microscopy imaging (TEM) and diffraction (TED) techniques are capable of providing surface structural information at the atomic level, such data would be suspect if obtained under conventional vacuum conditions (10^-6-10^-8 Torr). Ultrahigh vacuum (UHV) conditions are imperative during both preparation and observation of clean surfaces/interfaces. Conventional TEM techniques are very powerful for UHV-TEM investigations; however, the marriage of surface science and conventional TEM to yield an UHV-TEM is a complex task. These complexities and some of the results obtained using UHV-TEM and UHV-TED techniques for surfaces i.e. solid-vacuum interfaces will be illustrated.