STM Image Gallery       


STM Image Gallery - L'Hexagone

anchor A Copper Perspective Large Graphic
Title : A Copper Perspective
Media : Copper (111)

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Reminiscent of formal Japanese rock gardens, here we see ripples surrounding features on the copper (111) surface. The artists' fortunes took a major turn upward when they determined that the ripples were due to "surface state electrons." These electrons are free to roam about the surface but not to penetrate into the solid. When one of these electrons encounters an obstacle like a step edge, it is partially reflected. The ripples extending away from the step edges and the various defects in the crystal surface are just the standing waves that are created whenever a wave scatters off of something. The standing waves are about 15 Angstroms (roughly 10 atomic diameters) from crest to crest. The amplitude is largest adjacent to the step edge where it is about 0.04 Angstroms from crest to trough.
[Crommie, Lutz & Eigler] Library Link

anchor Circles on Circles Large Graphic
Title : Circles on Circles
Media : Unknown on Copper (111)

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Sometimes Nature is the best artist and all we need to do is catch it in the act. Here we see the result of imperfect sample preparation: two point defects adorning the copper (111) surface. The point defects (possibly impurity atoms) scatter the surface state electrons resulting in circular standing wave patterns.
[Crommie,Lutz & Eigler] Library Link

anchor Xenon Where? Large Graphic
Title : Oh Where, Oh Where Has My Xenon Gone? Oh Where, Oh Where Can He Be?
Media : Xenon on Nickel (110)

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The artists were known to supplement their income with daytime jobs as scientists and here we see their touch being applied to just such a daytime endeavor. The issue was 'Where does xenon bind on a metal surface?' (a burning issue if ever there was one). Here we see not one, but two images overlayed directly on top of one another. The rectangular array of the little magenta bumps are the tops of nickel atoms from one image poking up through the other image (you can do that with the computer). The images are of the same area of the nickel surface, just with and without the xenon atom (the big light blue bump in the center). Defects in the nickel surface are used to get precise registration information so the two images can be correctly overlayed. The computer was used to chop off the top of the xenon atom in order to peer through to the image of the surface without the xenon. When you look through the hole in the xenon atom you see a nickel atom located directly beneath. Evidently, xenon binds to the on-top site.

anchor Untitled Large Graphic
Title : Untitled
Media : Cesium & Iodine on Copper (111)

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Here we see the artists' first use of color mapping. Color is assigned to the surface not only by lights but by local curvature of the surface. This helps to delineate the shape of the object (which, for the curious, is a molecule that they assembled from 8 cesium and 8 iodine atoms).
[Hopkinson, Lutz & Eigler]

anchor Atomic Teeter-Totter Large Graphic
Title : Atomic Teeter-Totter
Media : Sodium & Iodine on Copper (111)

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The big glob is actually a well ordered crystal of 12 sodium and 16 iodine atoms that was assembled by Hopkinson in an attempt to build extended two dimensional structures. To his surprise and delight, the atoms had a mind of their own and spontaneously deformed into a three dimensional crystal. Hopkinson was pleased to discover that this had to do with the absence of commensurability between his crystal and the underlying copper lattice. Sliding the crystal over the surface caused different pairs of sodium atoms to sequentially pop up to the second layer and then pop down to the first layer -- a sort of teeter-totter effect.
[Hopkinson, Lutz & Eigler]

anchor Gadolinium Large Graphic
Title : Response of a Superconductor to a 4f Magnetic Impurity
Media : Gadolinium on Niobium (110)

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The upper image is a constant current topograph of three gadolinium atoms on a niobium (110) surface. The gadolinium atoms are used in this experiment as a magnetic impurity on top of the superconducting niboium sample. The lower image is a simultaneously acquired map of the conductance ( dI/dV ) measured at a D.C. bias just above the gap voltage of the niobium. The lower image shows the spatial extent of the bound state excitation in the superconductor. This excitation was found to fall off on a length scale that is much shorter than the superconductor's coherence length. It shows that the response of a superconductor to a magnetic impurity is dominated by this short range effect.