Figure 3: Differences in the alignment of water and ammonia molecules at the graphene/BTO interface.

(a,b) Shapes of water (a) and ammonia (b) molecules according to the VSEPR theory. Yellow clouds represent lone pairs of electrons in these molecules; arrows show the directions of the net dipole moments. (c) Idealized pictures of how the orientation of the molecular dipoles at the graphene/BTO interface translates into the polarization of BTO. (d,e) Orientations of the water molecules at the graphene/BTO interface for the cases when BTO is polarized downwards (d) and upwards (e). (f,g) Orientations of the ammonia molecules at the graphene/BTO interface for the cases when BTO is polarized downwards (d) and upwards (e).