Atom manipulation and nanostructure engineering on III-V semiconductor surfaces
Since its implementation in the early 1990s by the pioneering research of Eigler et al., STM-based atom manipulation has been applied mainly to adsorbates on metal surfaces. We have extended this technique to III-V semiconductor materials and achieved the reversible repositioning of native In adatoms on an InAs(111)A surface grown by molecular beam epitaxy. The repositioning is realized by transferring individual atoms between the surface and the STM tip and vice versa (vertical atom manipulation). Applying this technique in combination with scanning tunneling spectroscopy, we find that assembled In adatom chains (interatomic spacing 8.57 Å) exhibit confined quantum states implying substantial interatomic electronic coupling. Moreover, it is revealed that native In atoms in the InAs(111)A surface layer become bistable in vertical height when a nanostructure is assembled nearby. The binary (reversible) switching of surface atoms, driven by the STM tip, changes their charge state. Coupling between these switching units via Coulomb interaction is facilitated by assembling adatom chains, allowing us to explore the emergence of complex multiple switching at the atomic scale.
Figure:
Left panel: three-dimensional rendering of an STM image showing a sequence of ten In adatoms positioned by vertical manipulation on an InAs(111)A surface to form a linear chain. Pairs of adjacent adatoms can be reversibly switched by the STM tip to form a defect imaged as a large uniform protrusion, see the two features labeled as “In_pop”. Right panel: density-functional theory calculations reveal that the switching is due to surface In atoms in between of assembled In adatoms that become bistable in vertical height. This is evident from the blue curve showing the total energy of an infinite chain as the vertical height a surface In atom in between of chain atoms is varied.
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