Argon-filled nanocavities embedded in a single crystal of copper near the surface reflect electrons and induce a quantum well ͑QW͒ between the nanocavity and the atomically flat Cu͑001͒ surface. The spatial variation of conductance at the surface above the nanocavity was studied by scanning tunnelling microscopy and/or spectroscopy. Interference features were observed over several nanometers at some locations on the surface. In the ͓100͔ and ͓010͔ directions, the interference fringes propagate over longer distances up to tens of nanometers. In addition to these spatially resolved features, the conductance reveals an oscillatory behavior as a function of energy of injected electrons. A model taking into account the specific shape of the nanocavity, as well as the band structure of copper, allows us to simulate the spatial variation of the conductance in close agreement with the experiment. The modeling demonstrates that not only the specific shape of the subsurface nanocavity reflecting electrons is crucial to explain the observed pattern, but also the anisotropy of the band structure and the phenomenon of focusing of hot electrons connected to it. Our approach opens up opportunities to examine buried nano-objects with scanning tunneling microscopy, and also to study how the anisotropy of a crystal influences the spatial variation of QW properties.

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Scanning tunneling microscopy (STM) is used to study the STM-tip-induced movement of Co atoms in a diluted Co/Cu(001) surface alloy. By varying the sample temperature from 4 K up to room temperature, we measured the threshold temperature at which an incorporated Co atom can be moved, which is approximately 150 K. We propose that a vacancy-mediated mechanism is responsible for the observed movement, in which vacancies under the tip area exchange with an embedded Co atom. Finally, we present for the first time a selective movement of single Co embedded atoms.

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