Single Molecules Investigated using atomically functionalized qPlus Sensors

Single organic molecules were investigated using scanning tunnelling microscopy (STM), noncontact atomic force microscopy (NC-AFM), and Kelvin probe force microscopy (KPFM) employing a qPlus sensor [F. J. Giessibl, \textit{Appl. Phys. Lett.} \textbf{73}, 3956 (1998)]. The resolution was increased due to tip functionalization by atomic manipulation. Using NC-AFM and CO functionalized tips, atomic resolution on molecules [L. Gross \textit{et al. Science} \textbf{325}, 1110 (2009)] and molecular structure identification was demonstrated [L. Gross \textit{et al. Nature Chem.} \textbf{2}, 821 (2010)]. Moreover, the bond orders of individual carbon-carbon bonds in polycyclic aromatic hydrocarbons and fullerenes were distinguished [L. Gross \textit{et al.} \textit{Science} \textbf{337}, 1326 (2012)]. Using Xe terminated tips the adsorption height and tilt of individual molecules was determined [B. Schuler \textit{et al. PRL }\textbf{111}, 106103 (2013)]. With KPFM information about the intramolecular charge distribution was gained [F. Mohn \textit{et al.} \textit{Nature Nanotechnol.} \textbf{7}, 227 (2012)].