Role of tip structure and surface relaxation in atomic resolution dynamic force microscopy:CaF2(111)as a reference surface

Abstract

Reichling, Michael. 2002. Role of tip structure and surface relaxation in atomic resolution dynamic force microscopy: CaF2 (111) All material supplied via Aaltodoc is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user.Powered by TCPDF (www.tcpdf.org)Role of tip structure and surface relaxation in atomic resolution dynamic force microscopy: CaF 2 "111… as a reference surface By combining experimental dynamic scanning force microscope ͑SFM͒ images of the CaF 2 (111) surface with an extensive theoretical modeling, we demonstrate that the two different contrast patterns obtained reproducibly on this surface can be clearly explained in terms of the change of the sign of the electrostatic potential at the tip end. We also present direct theoretical simulations of experimental dynamic SFM images of an ionic surface at different tip-surface distances. Experimental results demonstrate a qualitative transformation of the image pattern, which is fully reproduced by the theoretical modeling and is related to the character of tip-induced displacements of the surface atoms. The modeling of the image transformation upon a systematic reduction of the tip-surface distance with ionic tips allows an estimate of the tip-surface distance present in experiment, where 0.28 -0.40 nm is found to be optimal for stable imaging with well-defined atomic contrast. We also compare the modeling with ionic tips to results for a pure silicon tip. This comparison demonstrates that a silicon tip can yield only one type of image contrast and that the tip-surface interaction is not strong enough to explain the image contrast observed experimentally. The proposed interpretation of two types of images for the CaF 2 (111) surface can also be used to determine the chemical identity of imaged features on other surfaces with similar structure.

Theories of scanning probe microscopes at the atomic scale

“…The white lines in the images are along the ͓2 11͔ direction and indicate the position of the scan lines. Reprinted with permission (Foster et al, 2002). ever, this peak is so small in comparison to the main peak over Ca that it has no affect on the contrast pattern.…”

“…Note that trajectories of only the bottom four atoms (one O 2Ϫ and three Mg 2ϩ ions) of the tip have been included. Reprinted with permission (Foster et al, 2002). which may have two signs of the electrostatic potential probing the surface. Although the MgO tip is clearly an idealized model, it seems to capture correctly both the possibility of different types of tip contamination by the surface and ambient ions and the strength of the shortrange chemical interaction.…”

Polarization effects in noncontact atomic force microscopy: A key to model the tip-sample interaction above charged adatoms

“…The proposed decay length of the interaction force in this model is about one order of magnitude perÅ and thus sufficiently small to explain atomic scale contrast on ionic surfaces. In a series of papers using different model tips on ionic as well as oxide surfaces, Shluger et al point out the importance of the polarization of both, tip and sample surface [14][15][16][17][18] . These extensive calculations consider, in particular, polarization effects; however, it seems difficult to separate them from the different other interactions also described in these works.…”

“…Our purpose is to show how SRE contribution can reproduce trends and orders of magnitude reported in the experiments by Gross et al 56 . However, it is not our intention to fit their results since that would require a fully atomistic description involving a complex simulation process [14][15][16][17][18] . …”

Site-specific force-distance characteristics on NaCl(001): Measurements versus atomistic simulations

“…In principle, similar information can be extracted from a series of images recorded at closely spaced constant distances or frequency shifts. 47 At room temperature, unavoidable drifts must be compensated, using, e.g., recognizable features as markers. Recently, a feature-tracking technique 48 was applied at room temperature to compensate drifts between successive frequency-distance measurements.…”