title: Nanoscale periodic modulations on sodium chloride surface revealed by tuning fork atomic force microscopy.
abstract: The sodium chloride surface is one of the most common platforms for the study of catalysts, thin film growth, and atmospheric aerosols. Here we report a nanoscale periodic modulation pattern on the surface of a cleaved NaCl single crystal, revealed by non-contact atomic force microscopy with a tuning fork sensor. The surface pattern shows two orthogonal domains, extending over the entire cleavage surface. The spatial modulations exhibit a characteristic period of 5.4 nm, along <110> crystallographic directions of the NaCl. The modulations are robust in vacuum, not affected by the tip-induced electric field or gentle annealing (<300 °C); however, they are eliminated after exposure to water and an atomically flat surface can be recovered by subsequent thermal annealing after water exposure. A strong electrostatic charging is revealed on the cleavage surface which may facilitate the formation of the observed metastable surface reconstruction.
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Kendal W
authors.initials: KW
authors.lastname: Clark
authors.forename: Shengyong
authors.initials: S
authors.lastname: Qin
authors.forename: X-G
authors.initials: XG
authors.lastname: Zhang
authors.forename: An-Ping
authors.initials: AP
authors.lastname: Li