Basic Mechanisms for Single Atom Manipulation in Semiconductor Systems with the FM-AFM

Abstract

This chapter unveils the atomic-scale mechanisms that are responsible for the room temperature manipulations of strongly bound atoms on semiconductor surfaces. First-principles simulations, matching the experimental forces, identify the key steps in two paradigmatic examples: the lateral manipulation of single adatom vacancies on the Si(111)-7×7 reconstruction in the attractive regime and the vertical interchange of atoms between the tip and the \(Sn/Si(111) - (\sqrt 3 \times \sqrt 3 )R30^ \circ\) surface by a gentle exploration of the repulsive force regime. Our calculations reveal that the outstanding experimental control of the manipulation under attractive forces comes from the localized reduction of the diffusion energy barriers induced by the tip for the different steps in the complex path followed by the Si adatom during the process. Using selective constraints, to face the difficulties posed by the complexity of a multi-atom contact and operation in the repulsive regime, our simulations illustrate how the vertical interchange can take place at the atomic scale, identify the crucial dimer structure formed by the closest tip and surface atoms, and discuss the role of temperature in the competition with other possible final outcomes (including atom removal or deposition by the tip).