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Manipulation is the most exciting feature of the non-contact atomic force microscopy technique as it allows building nanostructures on surfaces. Usually vertical manipulations are accompanied by an abrupt tip modification leading to a change of contrast. Here we report on low-temperature experiments demonstrating vertical manipulations of 'super'-Cu atoms on the p(2 Â 1) Cu(110):O surface, both extractions to and depositions from the tip, when the imaging contrast remains the same. These results are rationalized employing a novel and completely general method that combines density functional theory calculations for obtaining energy barriers as a function of tip height and a Kinetic Monte Carlo algorithm for studying the tip dynamics and extraction of manipulation statistics. The model reveals a novel multistep manipulation mechanism combining activated jumps of 'super'-Cu atoms to/from the tip with their drag by and diffusion on the tip.

A sharp probe tip with atomic scale stability is essential and desirable for noncontact atomic force microscopy (NC-AFM) studies at the atomic scale. We observed a Ge(001) surface using both a Si cantilever and a tungsten coated Si cantilever at room temperature in order to investigate the influence of the tip apex structure on the NC-AFM images. By using the Si cantilever, we first obtained four types of image at the atomic scale which can be explained assuming a dimer structure on the tip apex. On the other hand, the home-made tungsten coated tip, which has atomic scale stability and high electric conductivity, imaged the so-called ordered c(4 x 2) structure without any artifacts. The tungsten coated cantilever was found to have significantly higher performance for NC-AFM studies at the atomic scale than the Si cantilever.

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