Electrostatic Monolayering Produces Controlled Refractive Indices

Researchers from the Universidad Publica de Navarra in Spain and from Virginia Polytechnic Institute and NanoSonic Inc., both in Blacksburg, have shown that an electrostatic self-assembled monolayer process can create multilayered thin-film materials with a controlled refractive index.

The process involves depositing alternating positively and negatively charged layers on an ionized substrate, thus providing electrodynamically determined order at a molecular level. The method, published in the December issue of IEEE Photonics Technology Letters, could be applicable to a variety of diverse substrates, such as ceramics, metals and polymers, with different shapes and forms.

During test trials, the researchers formed multiple structure combinations of a cationic electrolyte formed from poly(diallyldimethyl ammonium chloride) and anionic electrolytes formed from poly(sodium 4-styrene-sulfonate) salt and a polymer dye. The trials produced films with a real refractive index that was controlled from 1.424 to 1.615 at a wavelength of 550 nm.