Instrumentation and Measurement Physics(DIMP)
Physique des instruments et mesures (DPIM)

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Hans HALLEN
North Carolina State University

Electron-induced motion of atoms: mechanisms and insights about hot electron transport

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Few-electron-volt energy electrons can induce motion of atoms in metals. We have observed oxygen motion in YBCO films with near-field optical microscopy (NSOM) and gold atom/vacancy motion in gold thin films using ballistic electron emission microscopy (BEEM). This somewhat surprising result can be attributed to localized bond breaking. The process results in an increased local diffusivity of oxygen in YBCO, and to subsurface terrace growth and/or mound formation in gold films. Tunnel electron energy dependence is measured. The threshold behavior is consistent with expectations from band structure. The effect is limited to a single grain in both cases, implying that these hot electrons do not cross grain boundaries -- the electrons loose their excess energy first.