  Scanning tunneling microscopy (STM) observations resolve the structure and
dynamics of metallic glass Cu$_{100-x}$Hf$_{x}$ films and demonstrate STM
control of aging at a metallic glass surface. Surface clusters exhibit
heterogeneous hopping dynamics. Low Hf concentration films feature an aged
surface of larger, slower clusters. Argon ion-sputtering destroys the aged
configuration, yielding a surface in constant fluctuation. STM can locally
restore the relaxed state, allowing for nanoscale lithographic definition of
aged sections.
