On the theory of scanning tunnel microscopy of nanosized clusters

摘要

Studies of nanosized clusters by scanning tunnel microscopy require not only the determination of the energy spectra and wave functions of the system but also information about the Green function and dynamics of intracluster transitions. For solving this problem, we suggest a modified variant of the theory of multiple scattering. This method allows analysis to be performed using physically visual concepts of tunneling electron transitions between centers that constitute a nanocluster. It is assumed that one-electron nanocluster states (or at least part of them) can be filled at an intermediate electron tunneling stage. Under these conditions, nanosystem energy levels are interpreted as resonances in the tunnel transition of an electron from the tip to the metal surface through centers situated on it. We reveal a peculiar behavior of such resonances in uniform chain structures situated parallel to the surface. If the tip is in the plane that is perpendicular to the surface and passes through the center of the chain, resonances related to antisymmetric states are completely absent in scanning tunnel microscopy spectra. The effects specified remain in force also in the presence of impurities (including spin-dependent impurities) in chains if these impurities do not distort their spatial symmetry.