Interface Imaging by Scanning Internal Photoemission

A scanning internal photoemission (SIP) technique is used to obtain a high resolution map or image of the potential energy barrier at an insulator interface. The image is produced by displaying the internal photocurrent produced by a monochromatic beam of light scanned across the sample. A special technique was developed for focusing the light to a spot less than one micrometer in diameter. Photoemission images of a Si-SiO
2
interface “stained” with a fractional monolayer of sodium are presented along with photoemission and reflectively images of a Nb
2
O
5
-Bi interface. These SIP images show inhomogeneities related to structural variations, impurities, and defects at the interface that previously were inaccessible to observation.