Visualization of\nAtomic Structures on Faceted and\nNonflat Surfaces by the Difference-of-Gaussians Approach

Detailed analysis of scanning probe microscopy (SPM)\ndata acquired\nfor faceted and nonflat surfaces is usually complicated due to the\npresence of a large number of surface areas tilted by large/variable\nangles relative to the scanning plane. As a consequence, standard\nmethods of elimination of global or local slopes by either plane subtraction\nor numerical differentiation seem to be ineffective. We demonstrate\nthat a simple difference-of-Gaussians procedure provides output data\ncorresponding to the projection of a considered surface onto the scanning\nplane without undesirable contrast modifications. This method allows\nus to suppress small-scale noise, minimize effects of finite slopes\nin the SPM images along both fast and slow scanning directions, and\nremove surface ripples without active participation of the operator.\nThis method can be applied for fast on-the-fly visualization of experimental\ndata and for more detailed analysis, including high-precision determination\nof lattice parameters and angles between translation vectors for surface\nreconstruction of different terraces or surface domains. In order\nto estimate geometrical distortions introduced by our procedure, we\ncompare the results obtained by the difference-of-Gaussians approach\nfor the tilted surfaces with direct image rotation in 3D space.