Recent Trends in Surface Characterization and Chemistry with High‐Resolution Scanning Force Methods

Abstract

The current status and future prospects of non-contact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM) for studying insulating surfaces and thin insulating films in high resolution are discussed. The rapid development of these techniques and their use in combination with other scanning probe microscopy methods over the last few years has made them increasingly relevant for studying, controlling, and functionalizing the surfaces of many key materials. After introducing the instruments and the basic terminology associated with them, state-of-the-art experimental and theoretical studies of insulating surfaces and thin films are discussed, with specific focus on defects, atomic and molecular adsorbates, doping, and metallic nanoclusters. The latest achievements in atomic site-specific force spectroscopy and the identification of defects by crystal doping, work function, and surface charge imaging are reviewed and recent progress being made in high-resolution imaging in air and liquids is detailed. Finally, some of the key challenges for the future development of the considered fields are identified.

Chemical Resolution at Ionic Crystal Surfaces Using Dynamic Atomic Force Microscopy with Metallic Tips

“…Therefore, it is impossible to assign image features to particular surface atoms without knowing the tip polarity. As a result, in spite of the many successes of NC AFM, interpretation, stability, and reproducibility of atomically resolved images are still hampered by difficulties in preparing and characterizing the tip apex and by structural instabilities caused by the strong tipsurface interaction [1]. In this Letter we demonstrate that metallic tips can resolve the surface atomic structure on ionic surfaces at tip-sample separations that avoid such instabilities and enable the unambiguous interpretation of atomic-scale chemical contrast.…”

“…Atomic force microscopy (AFM) operated in ultrahigh vacuum using the dynamical ''noncontact'' mode (NC AFM) is now a well established tool in surface science that is capable of imaging insulating as well as conducting surfaces with true atomic resolution [1,2]. The ability to characterize insulating surfaces and control surface processes down to the atomic scale is extremely important for numerous applications in chemistry, catalysis, nanoscience, and nanotechnology and can be achieved only using AFM.…”

Investigating atomic contrast in atomic force microscopy and Kelvin probe force microscopy on ionic systems using functionalized tips

“…Atomic force microscopy becomes increasingly important for studying surfaces on the atomic scale [1][2][3] as it provides atomic resolution and is not restricted to conducting samples. Furthermore, a wealth of information can be obtained by spectroscopic methods.…”

Understanding image contrast formation in TiO2with force spectroscopy

“…Calculations with model tips, like an MgO cube, 13 provide a basic understanding of the contrast in the protrusion and hole modes in TiO 2 in terms of electrostatic interactions controlled just by the tip apex polarity, as also proposed for other ionic surfaces. 14 The neutral case has been explained as due to the onset of covalent bonding with a nonpolar model Si tip. 10 However, a deeper, quantitative understanding of the contrast and the link with the tip structure requires us to go beyond just nc-AFM imaging.…”