Roles of a hard bubble suppression layer in ion-implanted bubble devices

A so-called hard bubble suppression (HBS) layer, formed throughout the surface of a bubble garnet film in an ion-implanted bubble device, has been investigated for its role in determining device operational characteristics. The HBS layer has a tendency to weaken charged wall strength and to diffuse bias field distributions by the charged wall at a propagation pattern cusp. Existence of the HBS layer degrades bubble generator current margins in a high current ampiltude region and bubble circulation bias margins in a low bias field region. A bubble detector/annihilator requires the HBS layer in a stretch and retract area for stable annihilation operation. In order to solve the contradictory roles in the device, a partial HBS ion-implantation process has been developed with He+ ions through a detector NiFe film and an SiO2layer masked with an Au lead conductor layer.