Development of an Ultrafast Scanning Tunneling Microscope

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An ultra fast scanning tunneling microscope will be constructed to image atomic motions over small distances in ultrahigh vacuum. By optimizing the instrument for imaging of small areas (less than 100 A across) atomic resolution imaging will be achieved at ratesup to 10 msec per image for full images, or 100 usec per scan line for narrow images. These rates are 10 to 1000 times faster than currently available UHV instruments. The system will operate at sample temperatures up to and above 600 C. This will permit the observation of dynamical processes on material surfaces with much faster timescales than is currently possible. Samples will also be characterized by LEED. In particular, we will use this instrument to study atomic diffusion of Si adatoms during annealing of the Si(100)-2x1 reconstructed surface as an investigation of the fundamentals of molecular beam epitaxy. We will also study the motion of surface atoms during melting of the Ge(111)-c(2x8) reconstructed surface.