Plasmon Absorption by Silver Nanoparticles on LiNbO3 Surface

Abstract

The morphology and optical spectra of silver nanoparticles sputtered onto lithium niobate substrates have been studied. Silver films with small mass thicknesses (from 0.5 to 3.0 nm) are found to form oblate spheroidal (disk-like) nanoparticles on the LiNbO3 surface, with a radius of about 7 nm and a height of about 1.2 nm. The corresponding absorption spectra contain a band with a maximum at 520–640 nm, which is associated with the excitation of nanospheroid’s plasmon mode. The location of the plasmon resonance maximum is found to depend on the sign of the lithium niobate surface charge, being equal to 564 nm for the positively charged surface and to 587 nm for the negatively charged one. A mechanism for the explanation of this dependence is proposed.