Tunnel resistance as a function of an Ir tip excursion z towards an Ir surface. Positive z corresponds to decreasing gap width. Transition to point contact is shown by an arrow for a tip excursion ze . The inset represents the degree of reproducibility of the transition. Image reprinted with permission from Ref. 32 .
A scanning electron microscopy image of two different electrochemically etched Cu-tip before (a) and after (b) a point-contact spectroscopy measurement with a piezopositioner.
Conductance as a function of the displacement of two gold electrodes with respect to each other in an MCBJ experiment at 4.2 K. Open squares represent the conductance trace while breaking the contact; a long plateau with a conductance near 1 G 0 is observed before the contact breaks. Open circles show instead the conductance trace while forming back the contact after breaking it; the electrodes need to displace towards each other by a slightly larger displacement than the one in which the electrodes stay in contact while opening the junction. The inset shows the return distance as a function of the length of the long plateau; the 5 Å offset is probably due to the elasticity of the atomic structure. Image reprinted with permission from Ref. 25 .
Construction of a quantum corral by STM manipulation at 6 K. (a)3D STM image taken during the construction of the corral. (b) 3D STM image after completion of the corral. White protrusions represent the 36 Ag adatoms which form the quantum corral (diameter: 31.2 nm). Image reprinted with permission from Ref. 57 .
(a) Structure model of a Au chain construction on top of a NiAl(110) surface. Au atoms bind preferably on top of bridge sites between Ni atoms. (b)–(f) STM constant current images (I = 1 nA; V sample = 2.1 V) showing different steps of the construction of a gold chain up to 20 atoms long (Au20). Image size is 95 Å by 95 Å. Image reprinted with permission from Ref. 66 .
The Au(110) surface with missing raw reconstruction (MRR). In different colors are shown the layers of chains, where the top one can be contacted and pulled with a STM tip.
Explanatory drawings for pulling angle α and tilting angle β; (a) tip (brown) in single-atomic contact with the atom at the end of the chain (grey); (b) freely suspended one-atomic gold chain after tip motion under an angle α in respect to the chain; (c) single ending chain of MRR; the target atom (grey) is surrounded by its five nearest neighbors (red); direction of tip motion indicates different distances between the tip position and the individual nearest neighbors resulting in breaking of bonds between target atom and nearest neighbors one after the other.
Illustration of chain pulling idea on the Au(110) single crystal (different gold layers color coded); pulling direction in dependence of pulling angle α and tilting angle β; (a) tip apex atom (brown) establishing contact with target atom on the end of the chain; definition of pulling direction (α,β) indicated by pointed direction (b) freely suspended monoatomic gold chain between tip and crystal after having been pulled off from the surface by tip retraction.
Drawing of an arbitrarily oriented surface in 3D (a) and STM image showing the exemplary chain direction (b). (a) By mx and by my the orientation of the simplified in 3D is defined. The direction of a single chain on the surface and the direction of the tip motion are indicated. The angle γ defines the direction of the chains in function of x and y. (b) STM image at 300 mK. The missing row reconstruction is displayed and by the orientation of the rows the chain direction γ is defined.
Conductance trace showing a 4 Å conductance plateau at 1 G 0. Atomic rearrangement in the junction is observable in the plateau as well as a jump out of contact and a jump into contact before the final breaking. The STM images on the left show the deposition of tip material in the center, the spot where tip and sample touched.
(a) Schematic representation of lifting a single molecular chain with an STM tip. After contacting the tip with the molecular chain this one can be lifted upon tip vertical retraction because of its flexibility and weak interaction with the substrate. (b)–(d) STM constant current images of the same area after different vertical manipulation steps (images sizes: 25.4 nm by 13.7 nm). The cross indicates the position of the tip during approach and retraction. The manipulated chain changes its shape during the pulling processes. The visible top chain serves as reference. Image reprinted with permission from Ref. 67 .
Article metrics loading...
Full text loading...