Effect of tip morphology on images obtained by scanning tunneling microscopy

Abstract
We present several images of the Si(111)7×7 reconstruction showing the effects of simultaneous tunneling from more than one atom on the tip. The observed topographies are described as a superposition of two 7×7 adatom patterns coming from a double tip, with a variety of distances between the two tips. Tips placed as closely as 3 Å can still produce two distinct images, demonstrating that each image originates from a single atom on the tip.