We use variable-temperature scanning tunneling microscopy (STM) combined with pattern recognition of STM images to demonstrate that the vicinal Ag(115) surface undergoes a true Kosterlitz-Thouless(KT)-type roughening transition. As predicted, the height correlation function remains finite below the roughening temperature and it evolves to a logarithmically diverging function at and above TR. From a quantitative analysis of the height fluctuations we derive a roughening temperature of TR= 465 ± 25 K. Recent diffraction experiments could not confirm a KT-type roughening transition on vicinal surfaces. We attribute this to small residual errors in local surface orientation, which overshadow the real thermally excited height fluctuations.

Phys. Rev. Lett.

Hoogeman, M. S., Klik, M. A. J., Schlößer, D. C., Kuipers, K., & Frenken, J. W. M. (1999). Real-space measurement of surface roughening. Phys.Rev.Lett., 82, 1728–1731.