Extended Data Fig. 4: The hydroxylated In2O3(111) surface with increasing water coverages in STM and AFM.
From: Direct assessment of the acidity of individual surface hydroxyls
The STM (top) and AFM images (bottom) were acquired at different regions of the surface. a1, Oxygen-terminated tip. b1–d1, OH-terminated tips. a, a1, Clean In2O3(111) surface. The contrast in STM (empty states) is dominated by the high density of states of the In(5c) and the lower density of states at the In(6c), which gives dark triangles. In AFM, the contrast is dominated by the topmost atoms of the surface, that is, the 12 O(3c) per unit cell. b, b1, Single dissociated water molecules, OWH and OSH. c, c1, Two and three dissociated water molecules per unit cell. d, d1, Saturation with three dissociated water molecules per unit cell in symmetry-equivalent sites, giving rise to a ‘propeller-like feature’ consisting of three brighter (OWH) and darker (OSH at O(β) site) at equivalent positions. For DFT calculations and structural relaxations see ref. 25.
