Piezoelectric and non-linear optical properties of alpha-quartz type Si1-xGexO2 single crystals

Single crystals of alpha-quartz type Si1-xGexO2 with x < 0.2 were grown in 0.05 M NaOH solution. Infrared measurements confirmed that crystals grown at high pressure and high temperature have a low -OH group defect content. After a few millimeters of crystal growth under these conditions, alpha(3500) reaches 0.1 cm(-1) and no free -OH are present. The d(11) value measured on an X-cut from the crystal with x = 0.0375 is 3.08 pC N-1 (+/- 0.15), in good agreement with the value of 2.97 pC N-1 obtained using density functional theory based calculations. Piezoelectric measurements were performed on the Si1-xGexO2 crystal with x = 0.0375, both at room temperature and after annealing at various temperatures. The piezoelectric signal of the crystal with x = 0.0375 and pure SiO2 disappears after annealing at 635 degrees C and 545 degrees C, respectively. Nonlinear optical ( NLO) properties of Si1-xGexO2 crystals were measured by Maker's fringe technique on Z-cut chi(11) (2) and their corresponding values for x = 0.023 and 0.028 are 1.3(2) pm V-1 and 1.6(2) pm V-1, respectively. These values are in good agreement with density functional theory based calculations. The light induced damage threshold values measured on Si1-xGexO2 crystals with x = 0.023 and 0.028 are very similar to that of alpha-quartz.