We present a reproducible technique for forming holes on a graphite surface with a scanning tunneling microscope. The holes have an average diameter of 40 Å (20 Å minimum) with an average resolvable spacing of 60 Å. Holes are produced by applying a short voltage pulse (3–8 V, 10–100 μs) across the tunneling gap which removes one or more layers of graphite in a small region directly below the tip. Arrays of hundreds of holes have been formed with yields as high as 99.6%. The writing process has a higher success rate in air or in the presence of water vapor. This suggests that the physical mechanism is a chemical process.
The initial stages and formation of subsequent layers in the room-temperature epitaxy of Ag on Au(111) have been studied using a scanning tunneling microscope in ultrahigh vacuum. Overall, the growth is layer by layer. At submonolayer coverages growth in fingerlike rows locked to the Au(111) (px J3) rectangular reconstruction is observed. One monolayer of Ag removes the substrate surface reconstruction.Higher coverages exhibit clustering and coalescence by growth in terrace shapes consistent with the symmetry of the Ag(111) surface.
High-resolution transmission electron microscopy and scanning tunneling microscopy have been combined to examine the structure of the thin "native" oxide that forms on silicon surfaces at room temperature. Differences in the cleaning procedures for silicon wafers may affect the morphology of this oxide and critically influence further processing on the silicon substrates. An etch that ended with a dip in hydrofluoric acid provided a thinner oxide and a lower interface step density than did a sulfuric peroxide treatment. The availability of complementary information from high-resolution transmission electron microscopy and scanning tunneling microscopy is discussed.
We have used scanning tunneling microscopy to characterize the surface of epitaxial gold on mica in air. We find that these surfaces are simple to prepare, are relatively inert to exposure to air or to water, and have atomically flat terraces extending for up to several hundred angstroms. The observed topography is consistent with the Au(111) surface. It is possible to produce bumps on the surface of less than 100 Å in size in a controlled manner by pulsing the tip voltage while scanning. Self-diffusion of gold is observed in the decay of written features and well as in the movement of existing terrace edges. In some cases, a periodicity in both the geometry of terrace edges and the spatial variation of surface diffusion rates suggest the presence of the 22×1 surface reconstruction.
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