Nanoscale 13, 13617-13623 (2021)
Benchmarking atomically defined AFM tips for chemical-selective imaging
Bertram Schulze Lammers1,2, Damla Yesilpinar1,2, Alexander Timmer2, Zhixin Hu3,*, Wei Ji4, Saeed Amirjalayer1,2,5, Harald Fuchs1,2 and Harry Mönig1,2,*
1 Physikalisches Institut, Westfälische Wilhelms-Universität, 48149 Münster, Germany
E-mail: harry.moenig@uni-muenster.de
2 Center for Nanotechnology, 48149 Münster, Germany
3 Center for Quantum Joint Studies and Department of Physics, Tianjin University, Tianjin, China
E-mail: zhixin.hu@tju.edu.cn
4 Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-Nano Devices, Renmin University of China, Beijing, China
5 Center for Multiscale Theory and Computation, 48149 Münster, Germany
Abstract
Controlling the identity of the tip-terminating atom or molecule in low-temperature atomic force microscopy has led to ground breaking progress in surface chemistry and nanotechnology. Lacking a comparative tip-performance assessment, a profound standardization in such experiments is highly desirable. Here we directly compare the imaging and force-spectroscopy capabilities of four atomically defined tips, namely Cu-, Xe-, CO-, and O-terminated Cu-tips (CuOx-tips). Using a nanostructured copper-oxide surface as benchmark system, we found that Cu-tips react with surface oxygen, while chemically inert Xe- and CO-tips allow entering the repulsive force regime enabling increased resolution. However, their high flexibility leads to imaging artifacts and their strong passivation suppresses the chemical contrast. The higher rigidity and selectively increased chemical reactivity of CuOx-tips prevent tip-bending artifacts and generate a distinct chemical contrast. This result is particularly promising in view of future studies on other metal–oxide surfaces.
