Optical band gap and ultralow dielectric constant materials prepared by a simple dip coating process

Abstract

A simple procedure for producing silica films containing ordered porous silica films, with pore sizes in the range of 40–1000 nm, is described. The precursors were prepared by mixing polystyrene latex (PSL) colloidal spheres and silica nanoparticles. The precursors were dipped vertically onto a silicon wafer or glass substrate and the PSL particles were then completely removed at a temperature of approximately 400 °C. This method permits the pore size to be selected by appropriate adjusting of the size of the PSL particles. The presence of an optical band gap, which is dependent on the dielectric constant periodicity of the material, was clearly observed. A simple medium effective model to calculate the effective refraction index of the film combined with a Bragg diffraction equation exhibit calculation results in agreement with the measured data. The film produced using this procedure has a dielectric constant as low as 1.192, thus confirming that the proposed method has also the potential for producing ultralow dielectric constant materials.