Nucleation of 1-µm bubbles via charged walls

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Abstract
The propagation and transfer of 1-&m bubbles via charged walls in ion-implanted contiguous-disk devices was previously reported. A novel bubble nucleator utilizing charged walls to provide a portion of the nucleation field, helping to define the spot where nucleation occurs and also reducing the required current, is described. Controlled nucleation of 1-& bubbles and propagation away from the nucleation site have been tested in several double garnet composites with different material Q factors (2 to 4) in the storage garnet layer. Typically, using a 0.1-&s current pulse along a 5-&m wide conductor, the nucleation current increases from 200 mA to over 800 mA over the entire bias field range (&15 percent) for propagation as the Q factor increases from 2 to 4. Compared to nucleators without charged wall assistance, the reduction in current level attributable to the charged wall is approximately 30-40 percent. This and other data are consistent with a model which assumes that nucleation takes place at the interface between the implanted and unimplanted layers, and that the charged wall contributes a field on the order of 0.5 & 4&M to the nucleation process. The collective operating margins for propagation (350 kHz), generation, transfer and annihilation of 1-&m bubbles along a short contiguous-disk pattern with a 4.5-&m device period are presented.