Author/Authors :
Armstrong، نويسنده , , Michael R. and Boyden، نويسنده , , Ken and Browning، نويسنده , , Nigel D. and Campbell، نويسنده , , Geoffrey H. and Colvin، نويسنده , , Jeffrey D. and DeHope، نويسنده , , William J. and Frank، نويسنده , , Alan M. and Gibson، نويسنده , , David J. and Hartemann، نويسنده , , Fred and Kim، نويسنده , , Judy S. and King، نويسنده , , Wayne E. and LaGrange، نويسنده , , Thomas B. an، نويسنده ,
Abstract :
Although recent years have seen significant advances in the spatial resolution possible in the transmission electron microscope (TEM), the temporal resolution of most microscopes is limited to video rate at best. This lack of temporal resolution means that our understanding of dynamic processes in materials is extremely limited. High temporal resolution in the TEM can be achieved, however, by replacing the normal thermionic or field emission source with a photoemission source. In this case the temporal resolution is limited only by the ability to create a short pulse of photoexcited electrons in the source, and this can be as short as a few femtoseconds. The operation of the photo-emission source and the control of the subsequent pulse of electrons (containing as many as 5×107 electrons) create significant challenges for a standard microscope column that is designed to operate with a single electron in the column at any one time. In this paper, the generation and control of electron pulses in the TEM to obtain a temporal resolution <10−6 s will be described and the effect of the pulse duration and current density on the spatial resolution of the instrument will be examined. The potential of these levels of temporal and spatial resolution for the study of dynamic materials processes will also be discussed.
