Precise formation technique of x-axis inversion regions on a quartz substrate and its applications to ultrasonic devices

This report represents a simple technique to form x-axis (electrical axis) inverted areas on a quartz plate with fine dimension control. After depositing a thin metal film of chromium, nickel or Nichrome on a quartz plate, the substrate is thermally treated. Thermal treatment at a temperature below the α-β transition temperature (573°C) produces x-axis inversion for the quartz under the film deposited area while the axis inversion does not occur for the undeposited area. The axis inversion phenomenon depends on the cut angle of the substrate. Dimension control of the axis inverted area is possible using a metal film pattern. Applications of the x-axis inversion phenomenon are proposed. For example, a configuration composed of two resonators with different modes on an AT-cut quartz plate is represented. One resonator is formed on the noninverted region and operates as an AT-cut resonator. The other resonator is formed on the axis inverted region and operates as a temperature sensor because of its large frequency temperature coefficient