Correlation between microstructure, particle size, dielectric constant, and electrical resistivity of nano-size amorphous SiO2 powder

Pure amorphous SiO₂ powder with nanometer size particles was exposed to various heat treatments up to 1200°C. The microstructure, particle size, dielectric constant and electrical resistivity of the powder were characterized after each heat treatment. It was found that the dielectric constant of the powder is higher compared to that of amorphous SiO₂ thin films. This enhancement is correlated with higher density of Si dangling bonds, which contribute to the polarization of the material. A major decrease in the dielectric constant takes place during heating up to 600°C where neither growth nor crystallization of the particles occur but only pronounced reduction in the density of the Si dangling bonds is observed. Pronounced growth and initial crystallization to a cristobalite phase of the powder particles occur at about 1100°C and have a minor effect on the dielectric constant. The Si dangling bonds also serve as electrical conducting centers in the powder and their annihilation due to the heat treatments is well observed as an increase in the electrical resistivity of the powder.