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Imaging electrostatic field
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On-surface chemical synthesis
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Structural and Electronic Properties of Nitrogen-Doped Graphene
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Role of the electrostatic force in AFM images
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Charge transport between two molecules
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Paper in ACS Nano
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Paper in Nature Comm.
Jul/15 High-resolution AFM images reported at room temperature. »more info

Paper in Nano Letters
Jun/15 The current and the force used for controlled atomic switching of silicon tetramer. »more info

O. Wichterle prize
May/15 M. Ondracek received O. Wichterle prize for outstanding young scientists at the AS CR. »more info

Paper in Nature Comm.

Recent developments in scanning microscopy enable us to resolve the chemical structure of individual molecules deposited on surfaces. The sub-molecular resolution of individual molecules opens up entirely new possibilities in the study of physical and chemical properties of molecular nanostructures. However, it was possible to carry out these measurements only at very low temperatures close to absolute zero with specially modified microscope tips. The modification consists in targeted location of just a single molecule (e.g. carbon monoxide) or a noble gas atom on the apex of the metal tip. The main obstacle to achieving sub-molecular contrast is the relatively weak signal-to-noise ratio detected during measurements. The presence of flexible particles on the apex of the tip results in a significant amplification of the signal, which allows us to achieve high-resolution images. However, such tips are stable only at very low temperatures, close to absolute zero. This condition has dramatically limited the use of this method in terms relevant to important chemical and biological processes, for which e.g. room temperature is essential.

We published in the July issue of the journal Nature Communications a new method that allows you to achieve sub-molecular resolution even at room temperature with standard tips. The optimum measurement parameters enabled a significant enhancement of the detection signal even without requirement of the special tip modification. This achievement pushes significantly the limits of the molecular resolution by means of the scanning probe microscopes. The possibility of imaging individual molecules on surfaces at ambient temperature represents essential prerequisite for the study of catalytic reactions on solid surfaces.

Fig.1 A) Experimental image with the sub-molecular resolution of PTCDA molecule on the silicon surface using an atomic force microscope at room temperature, B) calculated electron density distribution above a PTCDA molecule, which contributes to the formation of high-resolution AFM images, and C, D) optimized atomic structure of PTCDA molecule after deposition on the silicon surface obtained by quantum mechanical computer simulations (see [1]).


[1] K. Iwata et al.,Chemical structure imaging of a single molecule by atomic force microscopy at room temperature Nature Communications 6, 7766 (2015)