Extended Data Fig. 2: Distance-dependent STM/AFM images of the clean In2O3(111) surface.
From: Direct assessment of the acidity of individual surface hydroxyls
a, b, O-terminated tip. a, Constant-height STM image (tunnelling current, IT). b, Constant-height AFM images (frequency shift, Δf). From top to bottom, the tip–sample distance was progressively reduced in steps of about 50 pm. c, d, OH-terminated tip. c, Constant-current STM image. d, Same as c but the distance was reduced in steps of about 40 pm.
