Identification of OH groups on SrTiO₃(100)-(⁠$13×13$⁠)-R33.7° reconstructed surface by non-contact atomic force microscopy and scanning tunneling microscopy

Atomic resolution imaging of a SrTiO₃(100)-(⁠$13×13$⁠)-R33.7° reconstructed surface using non-contact atomic force microscopy (NC-AFM) and its simultaneous measurement with scanning tunneling microscopy (STM) is presented. Simultaneous STM and NC-AFM imaging reveals three patterns of image contrast depending on the tip apex condition and the relationship between the SrTiO₃(100)-(⁠$13×13$⁠)-R33.7° surface reconstructed structure and the NC-AFM image contrast. The NC-AFM image contrast variation is deduced from the tip apex polarity on the basis of an analysis of two images with opposite contrast. This interpretation is consistent with the results of simultaneous imaging of the SrTiO₃(100)-(⁠$13×13$⁠)-R33.7° surface. Furthermore, the results and interpretation identified an OH group, which is one of the surface defects, and this adsorption site.