Effects of the tip and surface electronic structure in STM images of the Cu(014)-O surface measured with W and MnNi probes
Chaika, A.N.1; Semenov, V.N.1; Nazin, S.S.1; Bozhko, S.I.1; Murphy, S.2; Radican , K.2; Shvets, I.V.2
1Russian Federation;
2Ireland

Our previous STM studies of the Cu(014)-O surface reconstruction by W probes [1] showed a selective visualization of atomic features which is related to the electronic structure of the tip and the surface. As a result, none of the STM images of the Cu(014)-O surface demonstrated true atomic arrangement in agreement with the overlayer model supported by XRD data [2] and DFT calculations [3]. Usually, one, two or three atomic rows within terraces consisting of four [100] oriented rows could be distinguished depending on scanning parameters and the tip state. To recover the Cu(014)-O surface atomic structure from the STM images one should combine information obtained by other techniques [2,3] and a number of images which reveal different atomic features within the terraces. A superposition of different images [1] allowed us to rebuild the atomic structure of the Cu(014)-O surface consistent with the overlayer model. In this report we present new experimental data obtained with antiferromagnetic (MnNi) and paramagnetic (W) probes. Just as for tungsten probes [1], MnNi probes allowed us to discriminate a number of atomic features within the terraces. However, in some cases additional unusual features (down to sub-atomic) could be resolved by employing MnNi tips. To qualitatively explain the observed unusual features we have performed tight-binding and DFT calculations of both the tip and the surface electronic structure. Their results as well as the studies of the tip-surface distance dependence of the Cu(014)-O STM images reveal that the selectivity of the STM probes and appearance of sub-atomic features in a number of STM images can be explained by a decisive contribution of different surface and tip electron states dominating at different scanning parameters. As an example, double imaging of the same atom by different legs of the tip dyz orbital could be the reason for the observed doubling of copper atoms along the close-packed {110} direction in the STM images of Cu(014)-O taken with the MnNi probes. This work was supported by the Russian Academy of Sciences and NT-MDT grants. [1] A.N.Chaika, S.I.Bozhko, JETP Lett. 82, 416 (2005) [2] D.A.Walko, I.K.Robinson, Surf. Rev. Lett. 6, 851 (1999). [3] E.Vileg et al., Surf. Sci. 516, 16 (2002).
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