Piezoelectricity and visible light luminescence in tetravalent-metal-doped poled silica thin films

It is known that poling treatment in germanium-doped silica (Ge:SiO2) glass raises their optical nonlinearity and produces the Pockels effect. This means that the poling treatment in Ge:SiO2 produces asymmetry in the glass. 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. However, less than a week later, piezoelectricity disappeared almost completely in all of the samples. To prevent piezoelectricity from disappearing, we attempted to pin the doping ions. We developed a pinning technique based on the superstructure of a Ge-Ti-Sn:SiO2 and Ge-Ti-Zr:SiO2. The superstructure was very effective in preventing piezoelectricity from disappearing. Furthermore, broadband visible light emission was observed in the proposed superstructure film. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 28–37, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20777