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Surface State Waves on Ag(111) at T = 5 K

In 1993 Eigler et al. observed for the first time standing waves on Cu(111) at 4 K, which originate from the well-known parabolic surface state crossing the Fermi level near the Gamma point (Ref. 1). These wave images occur typically at step edges and point defects. Standing waves have also been observed at elevated temperatures on the Au and Ag (111) surfaces (Refs. 2 and 3), although with reduced contrast.

With our low-temperature STM, we have imaged standing surface state waves on a Ag(111) film grown on HOPG, in the constant-current mode. They are surrounding two surface defects (see Figure1 below ). The two images show the standing waves (upper image) and the corresponding topography (lower image). Interesting enough, the hole defect and the adatom defect lead to distinct differences in the centers of the two circular waves which also exhibit nice interference effects.

We have also imaged waves near a screw dislocation on the same surface (see right figure below).The confinement of the surface state waves between the triangle shaped surface steps leads to pronounced constructive-interference maxima.

Standing waves

Figure 1: Acquisition parameters: top: sample voltage: 7 mV, current setpoint: 0.33 nA, 50 nm x 50 nm, bottom: like top with sample voltage: 0.32 V. The bottom image is 4-point averaged and the top image is low-pass Fourier filtered.

standing waves topography

Figure 2: Acquisition parameters: sample voltage: 7 mV, current setpoint: 0.33 nA, 65 nm x 62 nm. The image is low-pass Fourier filtered.



  1. M. F. Crommie, C. P. Lutz, and D. M. Eigler, Nature 363, 524 (1993).
  2. Y. Hasegawa and Ph. Avouris, Phys. Rev. Lett. 71, 1071 (1993).
  3. J. Li, W. D. Schneider, and R. Berndt, Phys. Rev. B. 56, 7656 (1997).