Pinholes may mimic tunneling

Interest in magnetic-tunnel junctions has prompted a re-examination of tunn eling measurements through thin insulating films. In any study of metal-ins ulator-metal trilayers, one tries to eliminate the possibility of pinholes (small areas over which the thickness of the insulator goes to zero so that the upper and lower metals of the trilayer make direct contact). Recently, we have presented experimental evidence that ferromagnet-insulator-normal trilayers that appear from current-voltage plots to be pinhole-free may non etheless, in some cases, harbor pinholes. Here, we show how pinholes may ar ise in a simple but realistic model of film deposition and that purely clas sical conduction through pinholes may mimic one aspect of tunneling, the ex ponential decay in current with insulating thickness. (C) 2001 American Ins titute of Physics.