Formation of Artificial Twinning Quartz Plate with x-axis Inversion Area by Laser Beam Irradiation

Abstract

We have previously reported an artificial twinning (x-axis inversion) technique by thermal treatment for a rotated Y-cut (RY-cut) quartz plate. However, it is impossible to form an arbitrary x-axis inversion pattern on a quartz plate using this technique. If the x-axis inversion pattern is artificially controlled, it is possible to produce new piezoelectric and/or optical devices. Twinning phenomenon is induced as follows. A metal film (i.e., Cr or NiCr) is deposited on the top surface of a rotated Y-cut quartz plate. Thermal treatment of the plate at about 520–540°C produces x-axis inversion of the quartz under the metal film. The x-axis inversion occurs due to stress that results from the difference in the thermal expansion between the quartz plate and the metal film. This paper presents a new twinning technique using laser scanning that has the potential to form an arbitrary twinning pattern. A quartz plate is placed on a movable stage in a vacuum chamber. On the plate surface, a metal film is deposited and the plate is heated at around 200–500°C. A laser beam is irradiated onto the plate. The metal film on the quartz plate absorbs the light energy and the plate is locally heated. This causes strong mechanical strain and twinning occurs around the irradiated area. As a result, a twinning area with an arbitrary pattern can be produced by scanning the laser spot along the metal film deposited on a RY-cut quartz plate. It was clarified that temperature gradient in the quartz plate is an important factor for twinning. Large temperature gradient produced in the plate by the laser beam irradiation drastically reduces the treatment temperature.