Wave packet dynamical simulation of scanning tunneling microscopy imaging of nanostructures

This work contains a detailed analysis of quantum effects which influence the scanning tunneling microscopic (STM) imaging process of carbon nanostructures. Time dependent scattering of electronic wave packets was calculated on a jellium potential model of the STM junction containing different arrangements of carbon nanotubes and point contacts. Distribution of the probability current and the probability density was derived from the time dependent wave function. The theory allowed one to identify components of pure geometrical origin responsible for characteristic distortions of the STM image of carbon nanosystems.
Several model systems were constructed, each model system consistedof a simulated tip, a support surface, and a carbon nanosystem. The tipconvolution effect was addressed by alculating line cuts over a nanotube; effect of point contacts was studied on the tunnel current; tunnel current for
a nanotube raft was calculated; tunnel current distribution was compared for both supported and unsupported nanotubes; electron wave backscattering was studied by simulating a capped tube; tunnel current distributions were calculated for different STM tip positions above a nanotube Y-junction.
The tunnel current flowing through the STM tip -- nanotube(s) -- support tunnel junction is mainly determined by the tip -- nanotube junction owing to its large tunnel resistance. The tunneling event through the STM model is characterized by two time scales, the nanotube is quickly "charged" with the wave packet coming from the tip then this "charge" flows into the support much slower