Chemical Identification of the Foremost Tip Atom of Atomic Force Microscope

Abstract

Chemical identification of individual surface atoms has been achieved by measuring the chemical bonds between tip and surface atoms using atomic force microscopy. On the other hand, the discrimination of chemical species at the tip apex is still a challenging task. Here, we perform the chemical identification of a foremost tip atom using bond energies measured on pre-characterized atomic species on a Si surface. We find that chemically different tips show different trends in the scatter plot of bond energies, and that Pauling's equation for polar covalent bonds well describes those trends. On the basis of this knowledge, in-situ chemical identification becomes possible, which can be applied to a broad range of elements in the periodic table. Using the chemically identified (here, Si and Al) tips, we determine the electronegativity of locally formed silicon oxide solely by experiments previously such determination was difficult without the help of theoretical calculations.