Comparison study of metal nanoparticles grown on polarity-patterned ferroelectrics by scanning probe microscopy

We report the surface distribution of metal (Ag, Au) nanoparticles (NPs) grown on polarity-patterned ferroelectrics by photochemical reaction. Single crystalline periodically polarity-patterned LiNbO ₃ (PPLN) was used as a ferroelectric substrate. The NPs were grown by the ultraviolet light exposure of the PPLN in the aqueous solutions including metals. Dimension and surface distribution of the NPs were measured, and the polarity of the patterned regions was identified by scanning probe microscopy. For both of Ag and Au, the NPs formed on +z polarity regions are larger and denser than those on -z polarity regions. In particular, the largest Ag-NPs were grown along the polarity boundary regions of the PPLN, whereas Au-NPs were not specifically grown on the boundary regions. Also, the size and density of the NPs increased with longer ultraviolet exposure time. We will discuss the difference of the surface distribution of the NPs depending on the polarity of ferroelectrics in terms of variation of the surface band structures and the electric field distribution induced by polarity bound charges, surface dipole formation, and defects. This study suggests the possibility of controlling the size and position of metal NPs on the surfaces by polarity patterning of the ferroelectrics.