Fig. 1: Cation ordering on as-cleaved mica.
From: Resolving the intrinsic short-range ordering of K+ ions on cleaved muscovite mica
a, b Crystal structure of mica. Al ions (blue) in the tetrahedral sheets are placed in a pseudo-random arrangement akin to Fig. 4e, showing one possible arrangement fitting the experimental data. a Side view of bulk mica. Cleaving occurs at the K layer, leaving half the K+ cations on each side. b Top view of the surface after cleaving. Before cleaving, each ditrigonal cavity (ring, highlighted in white) is occupied by one K+ ion. After cleaving, 50% K+ ions remain on each cleaved surface. c, d Atomically resolved constant-height nc-AFM images of mica after UHV cleaving, acquired with a CO-functionalized tip and a metal tip, respectively. The images were acquired at 4.7 K with different qPlus sensors and on different samples. Yellow (red) arrows highlight species with darker (fainter) contrast than average. e Fourier Transform of the image shown in panel (c). Yellow circles mark selected diffraction spots of the underlying bulk. Unit cells of the (almost) hexagonal lattice in panels (b), (d), and (e) are highlighted in yellow (strictly speaking, the muscovite unit cell is rectangular because the tetrahedral rings are not perfect hexagons).
