Piezoelectricity in Poled Silica Films with Tetravalent Metal Dopants

Piezoelectricity was produced in silica films with tetravalent metal dopants by poling. Poling treatment in germanium-doped silica (Ge:SiO2) glass films raises their of optical non-linearity and produces, among other things, the Pockels effect. We generated piezoelectricity in poled Ge:SiO2 glass thin films. Tetravalent-metal-doped SiO2 (M4 +:SiO2) films were prepared on Si substrates by RF magnetron sputtering. We used germanium, titanium, and tin as doping materials. The piezoelectricity of the films was compared with the piezoelectricity of quartz. Piezoelectricity of the same order of magnitude as that in quartz was observed in the M4 +:SiO2 films. However, less than a week later, the piezoelectricity disappeared almost completely in all the samples. To prevent the piezoelectricity from disappearing, we tried to pin the doping ions. We developed a pinning technique based on the structure of a Ge:SiO2-Ti:SiO2-Sn:SiO2-super-lattice. This super-lattice structure was very effective in preventing the piezoelectricity from disappearing.