  In this work, a very high, locally applied electric field was used to induce
whisker nucleation on an Sn film. The field was generated by using a conductive
AFM tip and applying a voltage bias between the sample and the conductive
cantilever>The tip-sample separation distance was thus controllable, and any
dielectric breakdown could be avoided. At locations where the AFM tip was
positioned for an extended period, minuscule whiskers were observed, whose
growth direction matched vertical orientation of the field.
