Abstract
Muscovite mica, KAl2(Si3Al)O-10(OH)(2), is a common layered phyllosilicate with perfect cleavage planes. The atomically flat surfaces obtained through cleaving lend themselves to scanning probe techniques with atomic resolution and are ideal to model minerals and clays.
Despite the importance of the cleaved mica surfaces, several questions remain unresolved. It is established that K+ ions decorate the cleaved surface, but their intrinsic ordering - unaffected by the interaction with the environment - is not known.
This work presents clear images of the K+ distribution of cleaved mica obtained with low-temperature non-contact atomic force microscopy (AFM) under ultra-high vacuum (UHV) conditions. The data unveil the presence of short-range ordering, contrasting previous assumptions of random or fully ordered distributions.
Density functional theory (DFT) calculations and Monte Carlo simulations show that the substitutional subsurface Al3+ ions have an important role for the surface K+ ion arrangement. Mica is a naturally occurring 2D mineral that has been heavily studied in many diverse areas.
Here authors present atomic force microscopy images to study the mica surface in ultra-high vacuum conditions; they unveil the distribution of its surface K+ ions and give insights into the distribution of subsurface Al3+ ions.