Ionic transport in fused silica and thin thermal SiO2 films

High temperature ionic conductivity of fused silica and thin SiO2 films has been investigated in the temperature ranges 700-1400 and 570-530 K respect ively by impedance spectroscopy measurements. The results are in agreement with the existence of extrinsic mechanisms in the ionic transport of both t ypes of silicon dioxide, due to the presence of dissociated sodium ions. Th e numerical analysis of the experimental results led to values of 1.3 and 0 .6 eV for the dissociation and migration energies, respectively. No influen ce of hydrogen content on alkali transport was found by considering wet and dry samples, at variance with results previously obtained on crystalline q uartz.