Height and friction AFM images for experiment Cd.16. a) calcite surface prior to the introduction of the Ca2+(aq)-Cd2+(aq)-HCO-3(aq) solution. The positions of 2 steps (1 and 2) are highlighted. b) 43 min. after introducing the solution, the advancement of steps 1 and 2 is clear in the topography image. In the friction image, the new growth layer (Ot-1) has a higher friction than the original calcite surface. The initial position of step 1 is marked as 1'. c) 80 min. after solution introduction, the further advancement of steps 1 and 2 is marked in the topography image. The friction image shows that step 2 has advanced well-over the initial position of step 1, growing a second layer of solid-solution (Ot-2) which possesses a higher friction than one layer of solid-solution (Ot-1). Image size: 3.3 μm × 3.3 μm.