Application of the KolibriSensor^® to combined atomic-resolution scanning tunneling microscopy and noncontact atomic-force microscopy imaging

Combined atomic-resolution scanning tunneling microscopy (STM) and noncontact atomic-force microscopy (NC-AFM) studies are carried out with the piezoelectric KolibriSensor in ultrahigh vacuum at room temperature. The sensor exhibits a very low spectral deflection noise density of only $6.5fm/Hz$ which favors in combination with its high spring constant of 540 000 N/m stable NC-AFM operation at subnanometer oscillation amplitudes. The authors present atomic-resolution imaging on the $Si(111)(7×7)$ surface recorded in STM and NC-AFM feedback mode. They find that the tip surface distance during atomic-resolution imaging on silicon is much smaller for NC-AFM compared to STM. It is shown that atomic-resolution NC-AFM and dynamic STM images of the same area on the $Si(111)(7×7)$ surface enable a discrimination of vacancies and adsorbates. Furthermore, the topography of graphite imaged in dynamic STM and NC-AFM feedback mode is compared.