Dynamic method for characterizing potential wells of bubbles under charged walls

The depth of the potential well Hwof a bubble under a charged wall in an ion-implanted propagation pattern has been characterized by a quasistatic measurement of bubble radius r versus bias field on and off the pattern. The well depth at collapse is found to be considerably larger than at lower bias fields. The extent Xwof the well, or alternatively its maximum gradient (∼Hw/Xw), is determined by a dynamic method as a function of in-plane field Hpand bias field. A pair of conductor lines is positioned above the ion-implanted structure and a pulsed field gradient is applied to drive the bubble out of the potential well. At long pulse lengths the critical gradientH'_{\max}needed to drive the bubble from the well is the maximum gradient of the well. Using a simple parabolic model for the well, the well's extent is given byX_{w}=2H_{w}/H'_{\max}. Experimental results for Xware considerably less than the observed minimum displacements at which a bubble will no longer spontaneously fall back into the well. These results indicate that the shape of the well is fairly flat with the principal rise in potential occurring at a large distance from the edge of the pattern.