Atomic scale imaging experimental techniques

During the preceding decade the theoretical research has also shifted, possibly as a result of detailed experimental findings. The emphasis is now on microscopic-level reconstruction of surfaces. Advanced surface diffraction and imaging techniques allow detailed characterization of surface morphology at an atomic level. These studies show that metal surfaces contain high concentrations of atomic steps, usually one atom in height, separated by well-ordered terraces. Statistical mechanical theories were developed to explain how atomic-scale processes can lead to the formation of these structures. 

The force microscope is also well suited for atomic and molecular manipulation as it allows the measurement and control of forces involved in the manipulation process. In fact, the force needed to move a Co atom or a CO molecule across a Cu(lll) surface has been quantified in a combined NC-AFM/STM experiment [238]. This experiment and other NC-AFM manipulation experiments have initially been performed at cryogenic temperatures in analogy to procedures known from STM manipulation. However, sophisticated experimental methods of atom tracking and feed-forward techniques also allow imaging, manipulation, and spectroscopy with atomic precision at room temperature [239-242]. Controlled vertical manipulation has been demonstrated by displacement of individual silicon atoms on a Si(lll)7x7 surface by soft nanoindentation [243] and lateral manipulation for adsorbates on a Ge(lll)-c(2x8) surface [244]. The concept of lateral manipulation has further been developed to create atomic structures on semiconductor surfaces at room temperature by using sophisticated manipulation protocols [245, 246]. Room-temperature, atomic-scale manipulation has also been achieved on insulating surfaces [247, 248] however, the processes involved are more complicated and the degree of control is lower in this case. 

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