Defects current oscillation

Figure Bl.19.6. Constant current 50 mn x 50 mn image of a Cu(l 11) surface held at 4 K. Tliree monatomic steps and numerous point defects are visible. Spatial oscillations (electronic standing waves) with a...

The artificial force is estimated from the intermolecular force field experienced by each molecule. Since the molecules are not in a perfect crystalline position, there always exists a force imbalance, which may be induced by thermal excitation, defects, non-crystalline structures, or other disturbing sources. At each time step the forces acting on each molecule by neighboring molecules are averaged, and the averaged force is used as the amplitude of the external force. Another parameter to be determined is the period of the external cyclic field, which is estimated by the oscillating frequency of the lattice constant divided by the atomic velocity. Moreover, to speed up numerical calculations the external cyclic field frequency of 500 GHz are imposed on some molecules selected from the amorphous-phase, although 2.45 GHz is applied for the experimental microwave assisted crystallization [3], and much lower frequencies are currently tried for the AMFC. 

Figure 24 Constant-current STM image of a Cu(lll) surface measured at 4K (Vt = 0.1 V and It = 1.0 nA). Spatial oscillations with a periodicity of 15 A are clearly emanating from monatomic step edges and point defects. (From Ref. 53.)...

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