Submicron-resolution study of a thin Ni crystal using a brightness-enhanced positron reemission microscope.

A 1500-A Ni(100) film is back illuminated with 5-keV positrons from a brightness-enhanced slow positron beam. Some of the positrons diff'use through the film and are emitted from the front surface by virtue of the Ni having a negative positron affinity. An immersion objective and projector lens form a 1150x image of the reemitted positrons at a 2D position-sensitive detector. With a resolution of 3000~ 1000 A we observe patches attributable to positron trapping at boundary layers inside the film. The advantages and ultimate capabilities of the positron reemission microscope are also discussed.