Manipulating Atoms and Molecules with STM

With an STM tip as engineering tool for surface modification, artificial atomic-scale architectures can be fabricated [70-72], chemical reactions on surfaces can be induced [63-65] and properties of single molecules can be studied at an atomic level [20, 21]. Manipulations with an STM tip can be performed by precisely controlling tip-sample interactions using tunneling electrons or the inhomogeneous electric field between the tip and sample. 

The following discussion introduces surface/sample modifications through the STM tip by focusing on manipulation of atoms. Manipulation of molecules is based on the same principles examples are listed at the end of this section. 

The STM tip has to be particularly well-defined for manipulation experiments. A controlled contact with the surface is often performed prior to manipulation experiments (see Tutorial 4 on STM tips). An STM manipulation process used to relocate single atoms or molecules across a surface is called a lateral manipulation. Such a lateral manipulation process involves (a) vertically approaching the tip towards the manipulated atom to increase the tip-atom interaction, (b) moving the tip parallel to the surface while the atom stays under the influence of the tip and moves laterally, (c) retracting the tip back to the normal scan height and thereby leaving the atom in its desired final location on the surface. 

The atom can be moved under the influence of the STM by either pulling, pushing or sliding the atom with the tip. 

Which of the movements is initiated can be controlled by choosing appropriate components of the force of the STM tip in the direction perpendicular (FT) and parallel (Fn) to the surface. 

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