Scanning tunneling microscopy evidences for surface electron scattering by underlying atoms

We have used a homebuilt scanning tunneling microscope (STM) to observe an atomically resolved underlying edge dislocation that occurred in the second layer of graphite. It showed evidence of variable interactions between the topmost two layers near the dislocation edge. Through a special thermal process, we will further demonstrate a variety of STM features scanned near grain boundaries. A collective interference model was proposed to explain these features. It views an STM image as the interference result of the electron waves in the first layer scattered by the potentials that come from the atoms in the first two layers with the second layer contribution being modified by some interlayer interaction factors. This model could correctly simulate all the observed features and revealed that the degree of the interlayer interaction could be quantitatively reflected by the bright-to-dark size ratio of the bright-dark pair at a lattice site. It thus provides a method of quantitatively studying interlayer interactions at the atomic level.