Simultaneous noncontact AFM and STM of Ag:Si(111)-(√3 x √3)R30°

The Ag:Si(111)-(root 3 x root 3)R30 degrees surface structure has attracted considerable debate concerning interpretation of scanning tunneling microscope (STM) and noncontact atomic force microscope (NC-AFM) images. In particular, the accepted interpretation of atomic resolution images in NC-AFM has been questioned by theoretical and STM studies. In this paper, we use combined NC-AFM and STM to conclusively show that the inequivalent trimer (IET) configuration best describes the surface ground state. Thermal-averaging effects result in a honeycomb-chained-trimer (HCT) appearance at room temperature, in contrast to studies suggesting that the IET configuration remains stable at higher temperatures [Zhang, Gustafsson, and Johansson, Phys. Rev. B 74, 201304(R) (2006) and J. Phys.: Conf. Ser. 61, 1336 (2007)]. We also comment on results obtained at an intermediate temperature that suggest an intriguing difference between the imaging mechanisms of NC-AFM and STM on structurally fluctuating samples. DOI: 10.1103/PhysRevB.87.075310